Endocrine

GLP-1 receptor agonists for type 2 diabetes management

Clinical Overview and When to Suspect GLP-1 RA Candidacy

— Semaglutide (Ozempic SC weekly, Rybelsus oral daily, Wegovy SC weekly for obesity)

— Dulaglutide (Trulicity SC weekly)

— Liraglutide (Victoza SC daily, Saxenda for obesity)

— Exenatide (Byetta BID, Bydureon weekly)

— Tirzepatide (Mounjaro/Zepbound) — dual GIP/GLP-1, technically a "twincretin" but tested on boards alongside GLP-1 RAs

— T2DM patient with established ASCVD, heart failure, or CKD not at A1c goal on metformin

— T2DM with BMI ≥27 and need for weight loss

— Patient wanting to avoid hypoglycemia (e.g., commercial driver, elderly)

— Failure of metformin monotherapy with A1c 7.5–9% range

Step 3 management: When the vignette emphasizes obesity, prior MI/stroke, or a patient who "wants to lose weight" alongside T2DM, the right next step is usually adding a GLP-1 RA with proven CV benefit — do not wait to maximize metformin first if cardiovascular indication is present. Conversely, if the dominant comorbidity is HFrEF or albuminuric CKD, pivot to SGLT2 inhibitor first. Recognize GLP-1 RAs as disease-modifying, not merely glucose-lowering, agents.

GLP-1 receptor agonists (GLP-1 RAs) are injectable (and one oral, semaglutide) incretin-based therapies that augment glucose-dependent insulin secretion, suppress glucagon, delay gastric emptying, and promote satiety.

Available agents in US practice:

When to suspect a Step 3 stem is steering toward a GLP-1 RA:

ADA 2024 Standards of Care: in T2DM with ASCVD or high CV risk, GLP-1 RA with proven CV benefit (semaglutide, dulaglutide, liraglutide) is recommended independent of A1c or metformin use.

In CKD or HF, SGLT2 inhibitors are preferred first; GLP-1 RA is preferred when weight loss or atherosclerotic risk reduction dominates the picture or when eGFR is too low for SGLT2i benefit on glycemia.

Presentation Patterns and Key History

— 55-year-old with T2DM (A1c 8.2%) on metformin 1 g BID, BMI 34, prior NSTEMI 2 years ago on statin/aspirin — needs add-on therapy

— 62-year-old T2DM with CKD stage 3, albuminuria, on metformin and lisinopril, A1c 7.8%, asking about weight loss

— 48-year-old T2DM, A1c 9.1%, occupation as long-haul truck driver, concerned about hypoglycemia on sulfonylurea

— Post-bariatric evaluation patient or one declining insulin who needs intensification

— Personal or family history of medullary thyroid carcinoma (MTC) or MEN 2 → absolute contraindication

— History of pancreatitis → relative contraindication; weigh risk

— Gastroparesis or severe GERD → GLP-1 RAs delay gastric emptying, worsen symptoms

— History of cholelithiasis or rapid weight loss → increased gallbladder events

— Diabetic retinopathy — rapid A1c drop with semaglutide associated with retinopathy worsening (SUSTAIN-6 signal); ensure recent dilated eye exam

— Pregnancy plans — discontinue at least 2 months before conception (semaglutide t½ ~1 week)

— Bariatric surgery history — efficacy preserved but tolerability matters

Board pearl: A vignette mentioning "father had thyroid cancer treated with thyroidectomy and pheochromocytoma" is a setup for MEN 2A — GLP-1 RA is contraindicated. Choose SGLT2 inhibitor or DPP-4 inhibitor instead. Always screen for personal/family MTC before prescribing.

Typical Step 3 vignette setups that should prompt GLP-1 RA selection:

Key history elements to elicit (and that question stems plant as clues):

Symptoms suggesting current poor control: polyuria, polydipsia, fatigue, blurred vision, weight gain on insulin or sulfonylurea.

Adherence and access: GLP-1 RAs are expensive; ask about insurance coverage, prior authorization, and shortages — a real Step 3 issue.

Physical Exam Findings and Baseline Assessment

— Vitals: BP (target <130/80 in most T2DM), HR (GLP-1 RAs cause modest HR increase ~2–4 bpm), orthostatics if autonomic neuropathy suspected

— Anthropometrics: weight, BMI, waist circumference (central adiposity drives insulin resistance and amplifies GLP-1 RA benefit)

— Skin: acanthosis nigricans (insulin resistance), necrobiosis lipoidica, injection-site lipohypertrophy from prior insulin

— Thyroid: palpate for nodules; a suspicious nodule warrants ultrasound and reconsideration of GLP-1 RA

— Abdominal: epigastric tenderness (pancreatitis risk), RUQ tenderness/Murphy (gallbladder), succussion splash or early satiety (gastroparesis)

— Cardiovascular: carotid bruits, peripheral pulses, JVP, S3 (HF), murmurs — ASCVD/HF reshape drug choice

— Neuro/foot exam: monofilament, vibration, pulses, ulcers — annual diabetic foot exam is mandatory

— Fundoscopic or referral confirmation: dilated eye exam within 12 months before rapid glycemic lowering

— GLP-1 RAs delay gastric emptying; ASA 2023 guidance recommends holding the day-of-procedure dose (daily agents) or the week before (weekly agents) prior to elective procedures requiring sedation to reduce aspiration risk.

— Document volume status: dehydration from GI side effects can precipitate AKI, particularly in elderly on ACEi/ARB/diuretic.

CCS pearl: When initiating a GLP-1 RA on the CCS, order at minimum: A1c, basic metabolic panel (eGFR), lipid panel, urine albumin-to-creatinine ratio, LFTs, weight, BP, and document a dilated eye exam referral. Schedule follow-up at 4–8 weeks for tolerance and at 3 months for A1c reassessment.

Exam is rarely diagnostic for "needing a GLP-1 RA" but supports comorbid risk profiling:

Hemodynamic assessment for the perioperative/CCS context:

Diagnostic Workup — Initial Labs and Baseline Testing

— HbA1c — confirms degree of hyperglycemia and sets target (generally <7%, individualized; <8% in frail elderly or limited life expectancy)

— Fasting plasma glucose and, if available, time-in-range data from CGM

— Basic metabolic panel — eGFR, K+, HCO3- (rule out DKA risk before assuming T2DM)

— LFTs — baseline ALT/AST; MASLD (NAFLD) is common and GLP-1 RAs improve hepatic steatosis

— Lipid panel — for ASCVD risk stratification and statin decisions

— Urine albumin-to-creatinine ratio (UACR) — informs CKD staging and choice between GLP-1 RA vs SGLT2i

— TSH — not routine, but if thyroid symptoms or nodules present

— Lipase/amylase — not routinely recommended at baseline or for monitoring per ADA, but obtain if symptoms develop

— Calcitonin — not recommended as routine screening (low PPV)

— If lean, young, ketosis-prone, autoantibody-positive → think T1DM or LADA; GLP-1 RAs are not first-line and insulin is required.

— C-peptide and GAD-65 antibodies if diagnosis ambiguous; low C-peptide + positive antibodies → autoimmune diabetes.

— 10-year ASCVD risk via Pooled Cohort Equations; T2DM is a risk enhancer.

— Document prior MI, stroke, PAD, coronary revascularization — these define established ASCVD and create a Class I indication for GLP-1 RA with proven benefit.

Key distinction: A patient with weight loss, polyuria, polydipsia, and ketones in urine is presenting with possible T1DM/DKA, not T2DM needing a GLP-1 RA. Order C-peptide, GAD-65, beta-hydroxybutyrate before assuming oral/injectable non-insulin therapy is appropriate. Misclassifying a T1DM as T2DM is a recurring Step 3 trap.

Baseline labs before initiating a GLP-1 RA:

Confirm type of diabetes:

ASCVD risk assessment:

Pregnancy test in reproductive-age women before initiation.

Diagnostic Workup — Advanced and Confirmatory Studies

— ECG — baseline; screen for prior silent MI (Q waves), LVH, conduction disease

— Echocardiogram — if HF symptoms, prior MI, or murmur; LVEF guides SGLT2i vs GLP-1 RA priority

— Stress testing — not routine for asymptomatic T2DM, but indicated if angina-equivalent symptoms before exercise prescription

— Coronary calcium score — reasonable in borderline ASCVD risk for statin decision-making, not for GLP-1 RA selection

— Confirm CKD with two eGFR values >3 months apart plus UACR

— Renal ultrasound if rapidly declining eGFR or proteinuria pattern atypical

— If ALT elevated, calculate FIB-4 score; consider transient elastography (FibroScan) for advanced fibrosis in MASLD

— Semaglutide and tirzepatide show histologic improvement in MASH trials

— Palpable nodule → thyroid ultrasound; if TI-RADS suspicious → FNA before GLP-1 RA initiation

— Routine calcitonin screening not recommended

— Symptoms of gastroparesis → gastric emptying scintigraphy before initiation; abnormal study is a relative contraindication

— Acute abdominal pain on therapy → lipase, contrast CT abdomen; sustained elevation or imaging changes → discontinue permanently

— Dilated fundus exam within 12 months; if proliferative retinopathy, treat (panretinal photocoagulation or anti-VEGF) before aggressive A1c reduction to mitigate early worsening

Board pearl: Rapid A1c drops >2 percentage points in 6 months can transiently worsen diabetic retinopathy (SUSTAIN-6 finding with semaglutide). Coordinate ophthalmology before aggressive titration in patients with known retinopathy — this is a patient safety, transition-of-care issue Step 3 likes.

Cardiovascular workup when GLP-1 RA selection hinges on ASCVD status:

Renal workup:

Hepatic workup:

Thyroid workup:

Gastric assessment:

Pancreatic assessment:

Ophthalmologic:

Risk Stratification and First-Line Management Logic

— Step 1: Lifestyle + metformin unless contraindicated

— Step 2: Stratify by comorbidity-driven priorities, not A1c alone

— Established ASCVD or high ASCVD risk (≥55 yo with ≥2 risk factors) → GLP-1 RA with proven CV benefit (semaglutide, dulaglutide, liraglutide) OR SGLT2i with proven benefit (empagliflozin, canagliflozin)

— HFrEF or HFpEF → SGLT2i (dapagliflozin, empagliflozin) — Class I

— CKD (eGFR <60 or UACR ≥30) → SGLT2i preferred; add GLP-1 RA if additional A1c lowering or weight loss needed, or if SGLT2i contraindicated

— Obesity-dominant phenotype → GLP-1 RA (semaglutide 2.4 mg or tirzepatide) for greatest weight loss

— Avoid hypoglycemia (commercial driver, frail elderly) → GLP-1 RA, SGLT2i, DPP-4i preferred

— Cost constraint → sulfonylurea, pioglitazone, NPH insulin remain options

— Tirzepatide 15 mg: ~20% body weight

— Semaglutide 2.4 mg: ~15%

— Semaglutide 1 mg (Ozempic): ~6–8%

— Liraglutide 1.8 mg: ~3–4%

— Dulaglutide, exenatide: 2–4%

— LEADER (liraglutide): ↓ MACE, CV death

— SUSTAIN-6 (semaglutide SC): ↓ MACE, ↑ retinopathy signal

— REWIND (dulaglutide): ↓ MACE in primary + secondary prevention

— PIONEER-6 (oral semaglutide): CV safety (noninferior, trend to benefit)

— Exenatide BID and lixisenatide: neutral

Step 3 management: When a vignette gives you a T2DM patient with prior MI + obesity + A1c 8%, the single best answer is to add a GLP-1 RA with proven CV benefit (semaglutide or dulaglutide) on top of metformin — even if A1c is "only" mildly above goal. The indication is cardiovascular, not just glycemic.

ADA 2024 simplified algorithm for T2DM pharmacotherapy:

Decision branches:

Comparative weight loss (approximate):

Comparative CV outcome data:

Pharmacotherapy — Dosing, Titration, and Drug Selection

— Start 0.25 mg weekly × 4 weeks → 0.5 mg weekly × 4 weeks → 1 mg weekly → max 2 mg weekly

— Slow titration minimizes nausea

— Start 3 mg daily × 30 days → 7 mg → 14 mg

— Take on empty stomach with ≤4 oz water, 30 minutes before food/other meds — adherence-critical

— 0.75 mg SC weekly → 1.5 mg → 3 mg → 4.5 mg max

— 0.6 mg SC daily × 1 week → 1.2 mg → 1.8 mg max

— 2 mg SC weekly (largely supplanted by newer agents)

— 2.5 mg SC weekly × 4 weeks → titrate by 2.5 mg every 4 weeks → max 15 mg weekly

— Greatest A1c and weight reduction in head-to-head (SURPASS trials)

— Inject any day of week, any time, with or without food (weekly agents)

— Rotate injection sites (abdomen, thigh, upper arm)

— Missed dose: if within 5 days for weekly agent, take ASAP; if >5 days, skip and resume schedule

— GI side effects: start low, go slow; small frequent low-fat meals; avoid greasy/spicy

— Delayed gastric emptying may slow absorption of oral meds — monitor INR if on warfarin, levothyroxine levels

— Concurrent sulfonylurea or insulin → reduce dose 20% to prevent hypoglycemia

Board pearl: GLP-1 RAs alone do not cause hypoglycemia because insulin secretion is glucose-dependent. Hypoglycemia in a vignette implies a co-prescribed sulfonylurea, glinide, or insulin — the right answer is to reduce the other agent, not stop the GLP-1 RA.

Semaglutide SC (Ozempic):

Semaglutide oral (Rybelsus):

Dulaglutide (Trulicity):

Liraglutide (Victoza):

Exenatide ER (Bydureon):

Tirzepatide (Mounjaro):

Counsel patients on:

Drug interactions:

Combination Therapy and Comparative Pharmacology

— Metformin + GLP-1 RA: foundational; preserves CV/weight benefits, low hypoglycemia

— Metformin + GLP-1 RA + SGLT2i: synergistic; reduces MACE, HF, CKD progression, A1c by ~2–2.5%; increasingly first-line in high-risk patients

— GLP-1 RA + basal insulin: powerful — addresses fasting (insulin) and postprandial (GLP-1 RA) hyperglycemia; fixed-ratio combos include iDegLira (degludec + liraglutide) and iGlarLixi (glargine + lixisenatide); reduce insulin-related weight gain and hypoglycemia

— Avoid GLP-1 RA + DPP-4 inhibitor — redundant mechanism; no added benefit, increased cost

— A1c >10%, symptomatic hyperglycemia, glucose >300, ketosis, catabolic weight loss → start basal insulin (glargine, degludec) and continue GLP-1 RA

— Use basal-only first, add prandial only if needed

— GLP-1 RA: 1.0–1.8%

— Tirzepatide: 1.5–2.2%

— SGLT2i: 0.5–1.0%

— DPP-4i: 0.5–0.8%

— Sulfonylurea: 1.0–1.5% (but weight gain, hypoglycemia)

— Basal insulin: no ceiling

— GLP-1 RAs cost ~$900–1,300/month without insurance

— Coverage requires prior authorization; documentation of metformin trial, BMI, A1c often required

— Compounded semaglutide carries safety/efficacy risks; FDA warns against unregulated compounds

— Drug shortages have been a recurring issue — counsel patients on alternatives

Step 3 management: A patient on metformin + glipizide + basal insulin with A1c 8.5%, BMI 36, prior MI — the best next step is stop glipizide, add GLP-1 RA, and reduce basal insulin by ~20%. This swap improves CV outcomes, drops weight, and lowers hypoglycemia risk simultaneously.

Combination strategies in T2DM:

When to add insulin despite GLP-1 RA:

Comparing classes at a glance (A1c reduction):

Cost and access (Step 3 health-systems context):

Special Populations — Elderly, Renal, and Hepatic Impairment

— Individualize A1c target: <7.5% in healthy elderly, <8.0–8.5% in those with comorbidity or limited life expectancy

— GLP-1 RAs are preferred over sulfonylureas and basal-bolus insulin due to low hypoglycemia risk

— Caution with frailty, sarcopenia, and anorexia — GLP-1 RA-induced weight loss in low-BMI elderly may worsen functional status

— Monitor volume status — nausea/vomiting → dehydration → AKI, especially with ACEi/ARB/diuretic combinations

— Falls and dizziness: rule out orthostasis from volume depletion

— Most GLP-1 RAs safe across all eGFR levels, including dialysis

— Exenatide: avoid if eGFR <30 (renally cleared)

— Liraglutide, dulaglutide, semaglutide, tirzepatide: no dose adjustment by eGFR

— In CKD with albuminuria, GLP-1 RAs reduce composite renal outcomes (FLOW trial, semaglutide) — they have a renal indication beyond just safety

— Watch for AKI from GI losses; pause therapy during acute illness

— GLP-1 RAs are not hepatically metabolized (cleared by proteolysis) — generally safe in mild–severe hepatic impairment

— Limited data in Child-Pugh C; use cautiously

— Beneficial in MASLD/MASH — improves steatosis, may reduce fibrosis progression

— Severe gastroparesis: contraindicated

— History of bariatric surgery: efficacy preserved; tolerability variable

Board pearl: A frail 82-year-old with T2DM, A1c 7.2%, BMI 22, and unintentional weight loss should not be started on a GLP-1 RA — the answer is to deintensify therapy and relax the A1c target to <8%. Step 3 frequently tests overtreatment in geriatrics.

Elderly (≥65, especially ≥75):

Renal impairment:

Hepatic impairment:

Drug-disease cautions:

Special Populations — Pregnancy, Pediatrics, and Reproductive Health

— GLP-1 RAs are not recommended in pregnancy (limited human data; animal teratogenicity signals)

— Discontinue at least 2 months before planned conception for semaglutide (long half-life ~1 week, washout ~5 weeks)

— Liraglutide: discontinue ≥1 month before conception

— Pregnant T2DM patients → insulin is the standard; metformin and glyburide are second-line and increasingly discouraged

— Counsel reproductive-age women on effective contraception; GLP-1 RAs may reduce oral contraceptive absorption due to delayed gastric emptying — consider backup contraception for 4 weeks after initiation/dose increase (especially tirzepatide labeling)

— Avoid; insufficient data on breast milk transfer; insulin remains preferred

— Liraglutide (Victoza): FDA-approved for T2DM ages ≥10

— Exenatide ER: approved ages ≥10

— Semaglutide (Ozempic): approved ages ≥12 (2023)

— Liraglutide (Saxenda) and semaglutide (Wegovy): approved for obesity ages ≥12

— Tirzepatide: not yet pediatric-approved

— Adolescent T2DM is aggressive; early intensive therapy improves long-term outcomes (TODAY trial showed early failure of monotherapy)

— GLP-1 RAs improve ovulatory function in PCOS via weight loss and insulin sensitization — pregnancies may occur unexpectedly; counsel accordingly

— Not FDA-approved for PCOS or infertility, but used off-label

Key distinction: Gestational diabetes or pregestational T2DM in pregnancy → answer is insulin, never GLP-1 RA. Conversely, a postpartum patient with T2DM who has finished breastfeeding and desires weight loss is an excellent GLP-1 RA candidate.

Pregnancy:

Lactation:

Pediatrics:

Reproductive endocrinology:

Complications and Adverse Outcomes

— Nausea (15–40%), vomiting, diarrhea, constipation, dyspepsia

— Mitigation: slow titration, small low-fat meals, avoid layering doses

— Usually improves over 4–8 weeks; persistent severe symptoms → reduce dose or discontinue

— Rare (~0.1–0.2%); causal link debated but FDA labeling warns

— Discontinue permanently if confirmed

— Increased cholelithiasis, cholecystitis (RR ~1.3); driven by rapid weight loss and gallbladder hypomotility

— Volume depletion from GI losses, especially with ACEi/ARB/diuretic; usually reversible

— Rodent signal; no confirmed human causation but black-box warning

— Absolute contraindications: personal/family history of MTC, MEN 2

— Associated with rapid A1c reduction; pre-treat proliferative retinopathy

— Reports of severe gastroparesis, sometimes persistent after discontinuation

— Aspiration risk with anesthesia — hold per ASA guidance before elective procedures

— ASA 2023: hold daily agents the day of procedure, weekly agents 1 week prior, or treat as full stomach with RSI

— EMA and FDA reviewed; no confirmed causal link, but counsel patients to report mood changes

— Emerging signal (2024 observational data); rare

Step 3 management: A patient on semaglutide presenting with epigastric pain radiating to the back, lipase 5× ULN → hold GLP-1 RA, admit for pancreatitis management (IV fluids, NPO, analgesia, imaging). Do not resume the drug after recovery — switch to an alternative class.

Gastrointestinal (most common):

Acute pancreatitis:

Gallbladder disease:

Acute kidney injury:

Medullary thyroid carcinoma / C-cell tumors:

Diabetic retinopathy worsening:

Injection-site reactions: mild, self-limited

Hypoglycemia: only when combined with sulfonylureas or insulin

Gastroparesis / ileus:

Pulmonary aspiration during anesthesia:

Suicidal ideation signal:

Non-arteritic anterior ischemic optic neuropathy (NAION):

When to Escalate Care — Consultation and Inpatient Triage

— Persistent vomiting with signs of dehydration → IV fluids, electrolyte correction

— Suspected pancreatitis (epigastric pain, vomiting, lipase elevation) → admit

— Suspected cholecystitis (RUQ pain, fever, Murphy's sign, leukocytosis) → surgery consult, RUQ ultrasound

— Hyperglycemic crisis (DKA, HHS) despite GLP-1 RA → admit; reassess diabetes classification (consider missed T1DM/LADA)

— Severe hypoglycemia → almost always points to coadministered sulfonylurea/insulin; adjust regimen

— Hospitalized patients on GLP-1 RAs: generally hold during acute illness; transition to basal-bolus insulin with correctional scale

— Resume GLP-1 RA at discharge if tolerating PO and clinically stable

— Perioperative: hold weekly agents 1 week prior, daily agents day-of per ASA; if not held, treat as full stomach with rapid-sequence induction or postpone elective procedure

— Endocrinology: A1c >9% despite combination therapy, suspected T1DM/LADA, complex insulin regimens

— Cardiology: established ASCVD requiring coordinated secondary prevention

— Nephrology: eGFR <30, rapid eGFR decline, refractory albuminuria

— Gastroenterology: gastroparesis evaluation, recurrent pancreatitis workup

— Bariatric surgery: BMI ≥35 with comorbidity or ≥40 without, refractory to pharmacotherapy

— Ophthalmology: pre-treatment of proliferative retinopathy before aggressive A1c lowering

— Diabetes educator / RDN: every patient at initiation; reinforces injection technique, diet

CCS pearl: On a CCS case, when a patient on semaglutide is admitted with pancreatitis: order hold semaglutide, NPO, IV LR, IV analgesia, lipase, CT abdomen with contrast, RUQ US to exclude gallstones, and document permanent discontinuation in the discharge summary with alternative agent plan (e.g., SGLT2i or pioglitazone).

Outpatient → urgent care/ED escalation:

Inpatient management considerations:

Specialty consultations:

Telephone triage red flags: severe abdominal pain, intractable vomiting, sudden visual loss, signs of bowel obstruction.

Key Differentials — Same-Category Therapeutic Choices

— Mechanism: inhibit degradation of endogenous GLP-1 (modest incretin effect)

— A1c lowering: 0.5–0.8% (less than GLP-1 RA)

— Weight neutral, no CV benefit (saxagliptin/alogliptin → ↑ HF hospitalization)

— Oral, well-tolerated, cheap generics

— Do not combine with GLP-1 RA

— Mechanism: glucosuria via SGLT2 inhibition in proximal tubule

— Benefits: HF (↓ hospitalization in HFrEF and HFpEF), CKD (slows progression), MACE reduction

— Risks: euglycemic DKA, genital mycotic infections, volume depletion, Fournier gangrene (rare)

— Often complementary to GLP-1 RA in high-risk patients

— Most potent A1c and weight reduction; tested separately from "pure" GLP-1 RAs but clinically comparable

— Adjunct to insulin in T1DM/T2DM; rarely used; similar GI side effects

— Cheap, effective; reduces stroke recurrence in insulin-resistant patients (IRIS trial)

— Risks: weight gain, edema, HF exacerbation, fractures, bladder cancer signal

— Effective, cheap, but hypoglycemia and weight gain

— No ceiling; needed for severe hyperglycemia or T1DM

Key distinction: GLP-1 RAs vs DPP-4 inhibitors — both target the incretin axis, but only GLP-1 RAs achieve pharmacologic receptor activation, with proven CV/weight/renal benefits. DPP-4i merely amplifies physiologic GLP-1 and is essentially weight neutral, CV neutral. Never combine the two.

Within T2DM pharmacotherapy, distinguish GLP-1 RAs from related classes:

DPP-4 inhibitors (sitagliptin, linagliptin, saxagliptin, alogliptin):

SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin, ertugliflozin):

Tirzepatide (dual GIP/GLP-1):

Amylin analogs (pramlintide):

Pioglitazone (TZD):

Sulfonylureas (glipizide, glimepiride):

Insulin (basal, prandial):

Key Differentials — Other-Category Causes and Mimics

— Lean adult with sudden hyperglycemia, ketonuria, autoantibody-positive (GAD-65, IA-2, ZnT8), low C-peptide

— Requires insulin, not GLP-1 RA monotherapy

— Strong autosomal-dominant family history, young onset, antibody-negative

— HNF1A-MODY responds to sulfonylureas; GLP-1 RA not first-line

— Steroid-induced → insulin or basal therapy preferred

— Pancreatogenic (type 3c) post-pancreatitis/pancreatectomy → insulin

— Cushing syndrome, acromegaly, pheochromocytoma → treat the primary endocrinopathy

— Hemochromatosis ("bronze diabetes") → phlebotomy, treat iron overload

— Semaglutide 2.4 mg (Wegovy), liraglutide 3 mg (Saxenda), tirzepatide (Zepbound) approved for chronic weight management with BMI ≥30, or ≥27 with comorbidity

— Different indication, different dosing

— Acute care with IV insulin, fluids, electrolytes — not the time for GLP-1 RA

— Diabetic gastroparesis worsens on GLP-1 RA; treat with prokinetics (metoclopramide short-term), dietary modification, glycemic control via other agents

— GLP-1 RAs contraindicated

— Cause is usually insulin/sulfonylurea, not GLP-1 RA; address those agents

Board pearl: A 28-year-old lean patient with new hyperglycemia, BMI 23, A1c 11%, ketones positive, and family history of "thyroid disease" → this is autoimmune (T1DM or LADA), not T2DM. Check GAD-65 and C-peptide, start insulin, and avoid GLP-1 RA. Do not be misled by "adult onset" — LADA is common.

Differentiating clinical scenarios where a "GLP-1 RA" answer might be wrong:

Type 1 diabetes / LADA:

MODY (maturokwartonset diabetes of the young):

Secondary diabetes:

Obesity without diabetes:

DKA/HHS at presentation:

Gastroparesis:

Anorexia, eating disorders, cachexia:

Hypoglycemia unawareness or severe recurrent hypoglycemia:

Secondary Prevention, Long-Term Plan, and Discharge Medications

— A1c <7% in most adults; individualize

— BP <130/80, statin therapy per ASCVD risk

— LDL <70 in established ASCVD; <100 in primary prevention with diabetes

— UACR <30 mg/g; treat with ACEi/ARB if albuminuric

— Weight reduction ≥5–10% for metabolic benefit

— High-intensity statin (atorvastatin 80 or rosuvastatin 40)

— Aspirin 81 mg + P2Y12 inhibitor per ACS protocol

— ACEi or ARB

— Beta-blocker if reduced EF or recent MI

— GLP-1 RA with proven CV benefit (semaglutide or dulaglutide)

— SGLT2i (empagliflozin or dapagliflozin) — especially if HF or CKD

— Metformin continued (hold transiently if AKI or contrast exposure)

— Mediterranean or DASH diet, ≥150 min/week moderate aerobic + 2 sessions resistance training

— Smoking cessation, alcohol moderation

— Sleep hygiene; screen for OSA (common in T2DM/obesity)

Step 3 management: A post-MI T2DM patient discharged on metformin and insulin with no SGLT2i or GLP-1 RA is a quality-of-care gap. The correct intervention is to add a GLP-1 RA (or SGLT2i) at discharge rather than deferring to outpatient follow-up — early initiation captures the cardioprotective benefit and reduces 30-day readmission.

Long-term goals on GLP-1 RA therapy:

Discharge medication bundle (post-MI T2DM patient as paradigm):

Lifestyle:

Vaccinations: annual influenza, COVID-19 boosters, pneumococcal (PCV20 or PCV15+PPSV23), hepatitis B (ages 19–59 with diabetes), RSV if ≥60, zoster if ≥50

Cancer screening: maintain age-appropriate; obesity-related cancers (colorectal, endometrial, breast, pancreatic) may decrease with sustained weight loss

Mental health: screen for depression (PHQ-9) annually; comorbid in 20–30% of T2DM

Follow-Up, Monitoring, and Counseling Cadence

— 2–4 weeks: phone/portal check-in for GI tolerance, injection technique, dose titration

— 3 months: A1c, weight, BP, basic metabolic panel; assess goal attainment

— 6 months: A1c, lipid panel, UACR, LFTs if MASLD; consider dose escalation if A1c >7%

— Annually: comprehensive diabetes review — dilated eye exam, monofilament foot exam, UACR, eGFR, lipid panel, A1c, dental, depression screen

— A1c every 3 months until at goal, then every 6 months

— Weight at every visit (target ≥5% loss at 3–6 months for "responder")

— Renal function every 6–12 months (more often if CKD or on ACEi/ARB)

— LFTs if MASLD or symptoms

— Lipase only if symptomatic, not routine

— Inject same day each week for weekly agents; use reminder apps

— Refrigerate unopened pens; opened pens stable at room temp ~30–56 days depending on agent

— Discard needles in sharps container — biohazard counseling

— Sick-day rules: hold during severe vomiting/dehydration; never stop insulin if T1DM; check ketones if T2DM with prolonged illness

— Travel: carry pen in original packaging with prescription label; TSA-compliant

— Discontinuation: weight regain common (~⅔ of lost weight within 1 year after stopping semaglutide 2.4 mg — STEP-1 extension); discuss long-term commitment upfront

— Refer to registered dietitian and certified diabetes care and education specialist (CDCES)

— DPP (Diabetes Prevention Program) for prediabetes

— Cardiac rehab post-MI/CABG

CCS pearl: Schedule a follow-up at 4 weeks after GLP-1 RA initiation to assess tolerance and titrate, plus a 3-month A1c check. Order dilated eye exam, foot exam, UACR, eGFR, lipid panel annually. Missing these ordering steps on CCS costs points even if the diagnosis is correct.

Follow-up schedule after GLP-1 RA initiation:

Monitoring parameters during therapy:

Counseling pearls:

Rehab/lifestyle support:

Ethical, Legal, and Patient Safety Considerations

— Discuss black-box warning for MTC and personal/family screening

— Disclose off-label use for weight loss if prescribed without T2DM, and cost implications

— Explain long-term commitment — discontinuation leads to weight regain and glycemic deterioration; this affects autonomy and adherence decisions

— Failure to hold GLP-1 RA preoperatively has caused aspiration events under anesthesia

— ASA 2023 guidance: hold weekly agents ≥1 week, daily agents day-of, or treat as full stomach with RSI

— Document hold instructions clearly in transition-of-care notes — surgical, anesthesia, primary care, and endocrine teams must align; this is a classic handoff failure Step 3 tests

— FDA has warned against unregulated compounded semaglutide/tirzepatide due to dosing errors, contamination, and counterfeit products

— Counsel patients to obtain medication from licensed pharmacies only

— During shortages, prioritize diabetes indication over weight-loss-only use ethically; some institutions have allocation policies

— Insurance step-therapy requirements raise equity concerns — be prepared to appeal denials with documentation

— Severe adverse events (anaphylaxis, severe pancreatitis, MTC) → report to FDA MedWatch

— Informed assent + parental consent; weight stigma counseling

— Document contraception counseling at initiation; report exposed pregnancies to manufacturer registries

— Screen for eating disorder history before prescribing for obesity; GLP-1 RAs can exacerbate restrictive patterns

— Counsel commercial drivers, pilots, machine operators on hypoglycemia risk only when combined with sulfonylureas/insulin

Step 3 management: A patient on weekly semaglutide presents for elective cholecystectomy and the surgical team did not receive medication reconciliation. The correct action is to postpone the elective procedure or proceed with full-stomach precautions (RSI) — and institute a systems-level fix: medication reconciliation protocols that flag GLP-1 RAs preoperatively.

Informed consent and shared decision-making:

Perioperative safety:

Compounded GLP-1 RAs:

Drug shortages and equitable access:

Mandatory reporting and disclosure:

Pediatric and adolescent considerations:

Pregnancy unintended exposure:

Disordered eating:

Driving and occupational safety:

High-Yield Associations and Rapid-Fire Clinical Facts

Board pearl: If the stem mentions MTC, MEN 2, severe gastroparesis, or pregnancy → GLP-1 RA is wrong answer. If the stem emphasizes ASCVD + obesity + T2DM → GLP-1 RA is right answer. Train this pattern recognition; it accounts for the majority of Step 3 endocrine pharmacology questions on this class.

Glucose-dependent insulin secretion → no hypoglycemia as monotherapy

Black-box warning: MTC and MEN 2 → absolute contraindications

Semaglutide = SC weekly (Ozempic, Wegovy) and oral daily (Rybelsus); long half-life ~1 week

Tirzepatide = dual GIP/GLP-1 → greatest A1c and weight reduction

Proven CV benefit: liraglutide (LEADER), semaglutide SC (SUSTAIN-6), dulaglutide (REWIND)

Neutral CV: exenatide, lixisenatide

Renal benefit: semaglutide (FLOW trial) — slows CKD progression in T2DM

MASH improvement: semaglutide, tirzepatide histologic benefit

Combine with: metformin, SGLT2i, basal insulin, pioglitazone

Do NOT combine with: DPP-4 inhibitor (redundant)

Reduce dose of co-prescribed sulfonylurea or insulin by ~20% to avoid hypoglycemia

Hold weekly GLP-1 RA 1 week before elective procedures (ASA 2023); daily agents day-of

Discontinue ≥2 months before conception (semaglutide); pregnancy → insulin

Pediatric approvals: liraglutide ≥10, semaglutide ≥12

Rapid A1c reduction → diabetic retinopathy worsening signal (SUSTAIN-6)

Gallbladder events ↑ with rapid weight loss

AKI from GI volume losses, especially with ACEi/ARB/diuretic

Weight loss approximate: tirzepatide 15 mg ~20%, semaglutide 2.4 mg ~15%, liraglutide 3 mg ~8%

Oral semaglutide: empty stomach, ≤4 oz water, 30 min before food/meds

Stopping = weight regain (⅔ within 1 year)

Off-label: PCOS, NASH, addiction (active research)

Cost ~$900–1,300/month; prior auth common

Backup contraception × 4 weeks after starting/dose-increasing tirzepatide (labeling)

Board Question Stem Patterns

— 58-year-old T2DM, A1c 7.6% on metformin, prior MI 1 year ago, BMI 32. Next step?

— Answer: Add semaglutide or dulaglutide (GLP-1 RA with CV benefit)

— Distractor: "intensify metformin" (already at max), "add sitagliptin" (no CV benefit)

— Patient eligible for GLP-1 RA but family history of "thyroid cancer treated with thyroidectomy at young age" or pheochromocytoma.

— Answer: Choose SGLT2i or alternative; avoid GLP-1 RA

— T2DM on glipizide + semaglutide presents with hypoglycemia

— Answer: Stop or reduce glipizide, continue semaglutide

— Patient on weekly semaglutide scheduled for elective surgery

— Answer: Hold semaglutide 1 week prior to procedure

— Reproductive-age woman on semaglutide planning conception in 3 months

— Answer: Discontinue ≥2 months before; switch to metformin or insulin

— Lean adult, recent weight loss, polyuria, ketones, antibodies positive

— Answer: Insulin; check GAD-65, C-peptide; not GLP-1 RA

— Patient with proliferative retinopathy and A1c 10.5%

— Answer: Ophthalmology referral first; aggressive glycemic lowering after retinopathy treatment

— Patient on liraglutide with epigastric pain, lipase 800

— Answer: Discontinue permanently; do not rechallenge

— Frail 82-year-old, BMI 22, A1c 6.8% on metformin + GLP-1 RA, weight loss, falls

— Answer: Deintensify — discontinue GLP-1 RA, relax A1c target

Step 3 management: Recognize that Step 3 questions emphasize the next best step in management rather than diagnosis. For GLP-1 RAs, the "next step" answer almost always involves either adding for comorbidity-driven indication, holding for safety, or substituting when contraindicated. Build a flowchart mentally before reading answer choices.

Pattern 1 — The cardioprotection pivot:

Pattern 2 — The MTC contraindication trap:

Pattern 3 — The hypoglycemia attribution:

Pattern 4 — The perioperative aspiration risk:

Pattern 5 — The pregnancy planning question:

Pattern 6 — The misdiagnosed T1DM:

Pattern 7 — The retinopathy precaution:

Pattern 8 — The pancreatitis decision:

Pattern 9 — The overtreatment in elderly:

One-Line Recap

GLP-1 receptor agonists are incretin-based, glucose-dependent therapies that lower A1c by 1–2%, drive substantial weight loss, and provide cardiovascular and renal protection — making them first-line add-ons (or substitutes for metformin) in T2DM patients with ASCVD, obesity, or CKD, provided no contraindications such as MTC/MEN 2, severe gastroparesis, or pregnancy exist.

Board pearl: GLP-1 RAs are no longer "diabetes drugs that also lose weight" — they are cardiometabolic disease-modifying agents whose indications are driven by comorbidity profile, not glycemia alone. Master the comorbidity-driven decision tree (ASCVD → GLP-1 RA; HF/CKD → SGLT2i; obesity → GLP-1 RA or tirzepatide; pregnancy → insulin) and the contraindication checklist, and the majority of Step 3 questions on this topic become pattern recognition rather than calculation.

Choose a GLP-1 RA with proven CV benefit (semaglutide, dulaglutide, liraglutide) for patients with established ASCVD or high CV risk — independent of A1c or metformin status; pair with SGLT2i in HF/CKD for stacked benefits.

Absolute contraindications: personal/family history of MTC or MEN 2, prior serious hypersensitivity; relative: severe gastroparesis, recurrent pancreatitis, pregnancy planning within 2 months, untreated proliferative retinopathy with very high A1c.

Safety bundle: titrate slowly to minimize GI effects, reduce concurrent sulfonylurea/insulin by ~20%, hold weekly agents 1 week before elective procedures (ASA 2023), counsel reproductive-age women on contraception, and monitor renal function during acute illness.

Step 3 testable pearls: no hypoglycemia as monotherapy, weight regain after discontinuation, rapid A1c drop can worsen retinopathy, do not combine with DPP-4 inhibitors, and remember that the question stem hints — "prior MI + BMI 34," "family thyroid cancer + pheochromocytoma," or "planning pregnancy" — define the right answer faster than memorizing trial names.