Eduovisual
Renal & Urinary
Hypokalemia: evaluation and replacement strategy
— Decreased intake (rare alone; anorexia, alcohol use disorder, tea-and-toast elderly)
— Transcellular shift (insulin, β2-agonists, alkalosis, refeeding, hypokalemic periodic paralysis, B12 therapy for megaloblastic anemia)
— GI losses (diarrhea, laxative abuse, vomiting/NG suction — note vomiting loses K⁺ mostly via renal wasting from alkalosis/aldosterone, not gastric fluid)
— Renal losses (diuretics, hyperaldosteronism, Bartter/Gitelman, RTA type 1/2, hypomagnesemia, amphotericin, cisplatin)
— Sweat losses (endurance athletes, burn patients)
— Patient on loop/thiazide diuretic with new weakness, cramps, or palpitations
— DKA patient receiving insulin (K⁺ falls predictably as it shifts intracellularly)
— Refractory hypokalemia → always check Mg²⁺; hypomagnesemia causes renal K⁺ wasting and prevents repletion
— Hypertension + hypokalemia + metabolic alkalosis → think primary hyperaldosteronism
— Young adult with normotension, hypokalemia, alkalosis, no diuretic use → think Gitelman or surreptitious vomiting
Board pearl: A potassium of 3.3 in a DKA patient is severe functional hypokalemia — total body K⁺ deficit is massive despite the lab value, and you must replete before/with insulin to avoid lethal arrhythmia.
— Generalized weakness, fatigue, myalgias, restless legs
— Cramps, especially lower extremity
— Severe (<2.5): ascending paralysis, hyporeflexia, respiratory muscle weakness, rhabdomyolysis (classic stem: marathon runner with K⁺ 2.2 and CK 18,000)
— Ileus and constipation from smooth muscle involvement
— Palpitations, ectopy, syncope
— Potentiates digoxin toxicity at any K⁺ <4.0 in a digoxin-treated patient
— Predisposes to torsades when QT-prolonging drugs coexist
— Polyuria/polydipsia (nephrogenic DI from impaired ADH response)
— Worsening glucose intolerance
— Metabolic alkalosis perpetuation
— Medications: thiazides, loops, β2-agonists (albuterol nebs), insulin, high-dose penicillins, amphotericin, foscarnet, laxatives, licorice (real glycyrrhizin — black licorice, chewing tobacco)
— GI: vomiting (look for dental erosions, parotid swelling, Russell sign in bulimia), diarrhea pattern, ostomy output, recent bariatric surgery
— Diet: alcohol use, eating disorder, refeeding after starvation
— Family history: Gitelman, Bartter, hypokalemic periodic paralysis (often Asian male, post-exercise or post-high-carb meal, may have thyrotoxicosis)
— BP pattern: young hypertensive on multiple agents with low K⁺ → primary aldosteronism screening
— Hypokalemia + HTN + alkalosis → mineralocorticoid excess
— Hypokalemia + normotension + alkalosis → vomiting, diuretic, Gitelman/Bartter
— Hypokalemia + acidosis → diarrhea or type 1/2 RTA
Key distinction: Vomiting produces low urine chloride (<20), whereas active diuretic use produces high urine chloride — this is the cleanest way to differentiate surreptitious vomiting from surreptitious diuretic abuse on the exam.
— Often unremarkable in mild hypokalemia
— Look for clues to etiology rather than to the K⁺ itself
— Hypertension → mineralocorticoid excess (primary aldosteronism, Cushing, Liddle, licorice), renovascular disease
— Normotension or orthostasis → GI losses, Gitelman, diuretic
— Tachyarrhythmia → severe depletion or coexisting digoxin/QT drug
— Bradycardia with AV block → consider digoxin toxicity potentiated by low K⁺
— Dental enamel erosion, parotid hypertrophy, Russell sign on knuckles → bulimia
— Moon facies, abdominal striae, supraclavicular fat pad → Cushing
— Hyperpigmentation → ectopic ACTH (small cell lung cancer with severe hypokalemic alkalosis is a classic stem)
— Diminished or absent deep tendon reflexes
— Proximal muscle weakness (have patient rise from chair without arms)
— Flaccid paralysis in severe cases — assess respiratory effort, NIF, vital capacity
— Irregular pulse from PACs/PVCs
— Listen for new murmur if heart failure is the diuretic driver
— Hypoactive bowel sounds, distention (ileus)
— Surgical scars suggesting prior bowel resection or bariatric procedure
— Hypovolemic (GI losses, diuretic excess): flat JVP, dry mucosa, orthostasis → expect secondary hyperaldosteronism amplifying K⁺ loss
— Euvolemic to hypervolemic with HTN: primary mineralocorticoid excess
— Hypervolemic with edema but on diuretics: HF/cirrhosis with diuretic-induced hypokalemia
CCS pearl: On a CCS case with weakness and K⁺ 2.4, your first three orders should be cardiac monitor, 12-lead ECG, and IV access — before you order the replacement infusion. The exam rewards safety-first sequencing.
— Repeat K⁺ if pseudohypokalemia suspected (extreme leukocytosis >100k drawn into room-temp tube can show falsely low K⁺ from WBC uptake — rare but tested)
— Order basic metabolic panel with magnesium, phosphorus, calcium
— Glucose — DKA, insulin therapy
— Bicarbonate drives the acid-base branch:
– Low HCO₃⁻ → acidosis pathway (diarrhea, RTA)
– High HCO₃⁻ → alkalosis pathway (vomiting, diuretics, mineralocorticoid excess)
— Spot urine K⁺ or 24-hour urine K⁺, ideally with creatinine
— Urine K⁺ <15 mEq/L (or <15 mEq/g Cr) → extrarenal loss (GI) or transcellular shift
— Urine K⁺ >15 (or >25 mEq/g Cr, or TTKG >4) → renal wasting
— Urine chloride for alkalotic patients: <20 = vomiting/contraction (chloride-responsive); >20 = diuretic, Bartter/Gitelman, mineralocorticoid excess (chloride-resistant)
— U waves (after T wave, most specific finding)
— T-wave flattening or inversion
— ST depression
— PR prolongation, prolonged QT → torsades risk
— Frequent PACs/PVCs, AV blocks
— Look for digitalis effect if relevant
— TSH/free T4 if periodic paralysis suspected (thyrotoxic hypokalemic periodic paralysis)
— Aldosterone:renin ratio if HTN + hypokalemia + alkalosis (off interfering meds when possible)
— Cortisol/dexamethasone suppression if Cushing features
— CK if weakness severe — rhabdo
— ABG/VBG for acid-base clarification
Board pearl: TTKG has fallen out of formal favor, but a spot urine K⁺-to-creatinine ratio >13 mEq/g Cr in a hypokalemic patient confirms renal potassium wasting — same answer, cleaner equation.
— Urine calcium-to-creatinine ratio is the splitter:
– Low (<0.1) → Gitelman (thiazide-like distal defect, also hypomagnesemia)
– High (>0.2) → Bartter (loop-like defect, normomagnesemic, presents earlier in life)
— Genetic testing confirms; rule out surreptitious diuretic with urine diuretic screen
— Plasma aldosterone-to-renin ratio (ARR) >20 with aldosterone >15 ng/dL → primary aldosteronism; confirm with saline suppression or oral salt load
— Adrenal CT after biochemical confirmation; adrenal vein sampling to distinguish unilateral adenoma (surgical) from bilateral hyperplasia (medical)
— Low aldosterone + low renin → consider Liddle, licorice, Cushing, 11β-HSD deficiency
— High renin + high aldosterone → renovascular HTN; order renal duplex or CTA
— Urine anion gap (Na + K − Cl):
– Negative → GI bicarbonate loss (diarrhea)
– Positive → distal RTA (type 1) — confirm with urine pH >5.5 despite acidemia
— Type 2 (proximal) RTA → bicarbonaturia, urine pH variable, often Fanconi features (glycosuria, phosphaturia, aminoaciduria)
— TSH (thyrotoxic form, especially Asian males)
— Genetic testing for CACNA1S/SCN4A mutations
— Provocation testing only in specialty setting
— Adrenal CT for primary aldosteronism or Cushing
— Renal ultrasound with Doppler for renovascular HTN
— Pituitary MRI if ACTH-dependent Cushing
— Repeat magnesium — refractory hypokalemia without correcting Mg is a guaranteed wrong-answer setup
Step 3 management: When you confirm primary aldosteronism, the next best step is adrenal CT followed by adrenal vein sampling in candidates ≥35 with biochemical confirmation, because CT alone misclassifies ~25% of cases.
— Mild (3.0–3.4), asymptomatic, low-risk patient: oral repletion outpatient, address cause
— Moderate (2.5–2.9): oral ± IV repletion, telemetry if cardiac comorbidity
— Severe (<2.5), symptomatic, ECG changes, on digoxin, post-MI, arrhythmia, DKA: IV repletion with continuous cardiac monitoring
— Active ischemia or recent MI (keep K⁺ >4.0)
— Heart failure on digoxin (keep K⁺ >4.0)
— Cirrhosis with hepatic encephalopathy risk
— Patients on QT-prolonging drugs or with congenital long QT
— DKA/HHS receiving insulin
— Severe asthma exacerbation on continuous β-agonists
— For every 0.3 mEq/L decrease in serum K⁺ below 4.0, total body deficit ≈ 100 mEq
— A patient with K⁺ 3.0 has roughly a 300 mEq deficit; a patient with K⁺ 2.0 may have >600 mEq deficit
— This is approximate — recheck levels frequently rather than calculating to perfection
— Oral KCl is preferred whenever the patient can take PO and is not critically symptomatic; safer, slower equilibration
— IV KCl when oral not feasible, severe deficit, symptomatic, or NPO
— Combination when severe but tolerating PO
— Check and replete magnesium before/with K⁺ if Mg <2.0
— Stop or dose-reduce the offending drug (or pair thiazide with K-sparing agent)
— Treat the underlying disorder (anti-emetics, anti-diarrheals when appropriate, spironolactone for aldosteronism)
CCS pearl: On CCS, when you see K⁺ <3.0 with ECG changes, your order set is: cardiac monitor → IV access ×2 → IV KCl in saline (NOT dextrose — dextrose triggers insulin release and drops K⁺ further) → Mg²⁺ → recheck K⁺ in 2–4 hours.
— Standard dose 20–40 mEq PO every 2–4 hours for moderate deficits, up to 40–80 mEq total per dose limit
— Each 10 mEq raises serum K⁺ by ~0.1 mEq/L transiently
— Formulations: extended-release wax matrix or microencapsulated tablets (less GI irritation), liquid (faster but bitter), effervescent
— Take with food and water; avoid lying down for 30 minutes (esophagitis risk, especially with strictures or anticholinergics)
— Peripheral line: maximum 10 mEq/hr, concentration ≤10 mEq/100 mL (burns and phlebitis if higher)
— Central line with telemetry: up to 20 mEq/hr, occasionally 40 mEq/hr in critical settings (ICU only)
— Always in saline, not dextrose-containing fluids
— Recheck K⁺ every 2–4 hours during active repletion
— KCl — first-line; corrects both K⁺ and the chloride deficit of metabolic alkalosis (vomiting, diuretics)
— K-citrate or K-bicarbonate — preferred when hypokalemia coexists with metabolic acidosis (RTA, diarrhea); citrate also helps in calcium stone formers
— K-phosphate — when hypophosphatemia coexists (DKA, refeeding)
— Mg²⁺ <2.0 → 2 g IV magnesium sulfate over 1–2 hours, or oral Mg oxide/gluconate outpatient
— Without Mg correction, renal K⁺ wasting continues and K⁺ won't normalize
— Spironolactone or eplerenone for primary aldosteronism, cirrhosis, heart failure
— Amiloride or triamterene for Liddle syndrome, lithium-induced wasting, or thiazide-induced hypokalemia when ACE-I/ARB insufficient
— ACE-I/ARB in HF/HTN patients on diuretics can blunt K⁺ losses
Board pearl: Never mix KCl into a hanging bag at the bedside — pre-mixed bags only. This is a tested patient-safety item; medication errors with bolus KCl are lethal and a sentinel event.
— K⁺ >5.2: hold KCl, start insulin, recheck in 1–2 hours
— K⁺ 3.3–5.2: add 20–30 mEq KCl to each liter of IVF, continue insulin
— K⁺ <3.3: hold insulin, give 10–20 mEq/hr KCl until K⁺ >3.3, then resume insulin
— Rationale: insulin drives K⁺ intracellularly; giving insulin to a hypokalemic patient triggers fatal arrhythmia
— Anticipate hypokalemia, hypophosphatemia, hypomagnesemia in malnourished patients restarting nutrition
— Start feeds at 25–50% of goal, supplement thiamine first, replete K/Mg/Phos prophylactically, check labs every 12 hours for 72 hours
— Non-selective beta-blocker (propranolol) is preferred — corrects underlying shift
— Give cautious K⁺ repletion; rebound hyperkalemia common because total body K⁺ is normal
— Treat hyperthyroidism definitively
— Unilateral adenoma → laparoscopic adrenalectomy
— Bilateral hyperplasia → spironolactone (50–100 mg/day) or eplerenone (preferred in young men due to gynecomastia with spironolactone, and in pregnancy planning)
— Add ACE-I/ARB first (often sufficient)
— Add K-sparing diuretic (amiloride, triamterene, or low-dose spironolactone) if persistent
— Consider switch from thiazide to chlorthalidone with K-sparing combo
— Lifelong oral KCl + Mg supplementation
— Add spironolactone, amiloride, or NSAIDs (Bartter) to reduce wasting
— Liberal salt intake
Step 3 management: A hypertensive patient on hydrochlorothiazide with persistent K⁺ 3.1 despite 40 mEq KCl daily should prompt either adding an ACE-I/spironolactone OR screening for primary aldosteronism with ARR — don't just keep escalating KCl.
— Higher baseline use of diuretics, laxatives, and ACE-I/ARBs creates competing risks for both hypo- and hyperkalemia
— Polypharmacy review is the single highest-yield intervention — Beers criteria flag chronic high-dose thiazides without K⁺ monitoring
— Decreased thirst and concentrating ability worsen volume contraction and amplify K⁺ losses
— Esophageal dysmotility raises risk of KCl tablet-induced ulceration — prefer liquid or microencapsulated forms; ensure upright posture for 30 minutes
— Falls risk from muscle weakness — assess gait before discharge
— Cognitive impairment may mask symptoms; pharmacist medication reconciliation at transitions
— Replete more cautiously — diminished renal K⁺ excretion means overshoot risk
— Typical dose reduction: start with half the usual oral dose, recheck within 24 hours
— Avoid ACE-I/ARB/spironolactone combinations when GFR <30 unless tightly monitored
— Patients on dialysis: hypokalemia usually means excessive dialytic removal (high K⁺ bath needed, especially in malnourished) or interdialytic GI loss
— Hypokalemia worsens hepatic encephalopathy by promoting renal ammoniagenesis — keep K⁺ ≥4.0 in encephalopathic patients
— Diuretic strategy: spironolactone:furosemide in 100:40 ratio preserves K⁺ balance
— Watch for concurrent hyponatremia; correct K⁺ first if both are low — replacing K⁺ raises Na⁺
— Lactulose-induced diarrhea is a common iatrogenic cause
— Target K⁺ 4.0–5.0
— When loop diuretic causes K⁺ <4.0, uptitrate MRA (spironolactone/eplerenone) before adding KCl supplements
— Monitor labs 1 week after any diuretic or MRA change
Key distinction: In cirrhosis, furosemide alone causes hypokalemia; spironolactone alone causes hyperkalemia — the 100:40 (spiro:furosemide) starting ratio keeps K⁺ neutral. This is a frequent stem.
— Physiologic mild decrease in serum K⁺ (~0.2–0.3 mEq/L) due to volume expansion — usually clinically irrelevant
— Hyperemesis gravidarum is the most common pathologic cause — vomiting → metabolic alkalosis → renal K⁺ wasting
– Treat with IV hydration, antiemetics (ondansetron, doxylamine-pyridoxine), KCl repletion
— Primary aldosteronism in pregnancy: spironolactone is contraindicated (anti-androgen effects on male fetus); use eplerenone or amiloride
— Preeclampsia + MgSO₄ therapy: monitor K⁺ along with Mg, calcium, reflexes
— Bartter syndrome typically presents in infancy with polyuria, failure to thrive, polyhydramnios history
— Gitelman presents later, often in adolescence/adulthood with cramps, tetany
— Diarrheal illness is the leading acquired cause; oral rehydration solutions contain K⁺ for this reason
— Cystic fibrosis: salt and K⁺ losses through sweat, especially in hot climates
— Pediatric doses: 0.5–1 mEq/kg/dose oral KCl, IV repletion at 0.5–1 mEq/kg/hr with continuous monitoring
— Bulimia → vomiting/laxative-induced hypokalemia, metabolic alkalosis, low urine Cl
— Anorexia → poor intake, refeeding risk
— Multidisciplinary referral: psychiatry, nutrition, primary care; do not focus only on the electrolyte
— Inpatient admission criteria include K⁺ <3.0, severe bradycardia, hypoglycemia
— Heat-related K⁺ losses through sweat
— Rhabdomyolysis may transiently cause hyperkalemia, but exertional hypokalemia can also occur with chronic conditioning
— Toluene inhalation (glue/paint sniffing) → distal RTA-like hypokalemic acidosis
— Chronic alcohol use → multifactorial (poor intake, vomiting, hypomagnesemia, diarrhea)
Board pearl: A pregnant woman with HTN, hypokalemia, alkalosis, and a suspicious adrenal nodule needs eplerenone, not spironolactone — and surgery is generally deferred until after delivery unless catecholamine-secreting tumor is also present.
— Ventricular arrhythmias: PVCs, NSVT, sustained VT, torsades de pointes, VF
— Increased digoxin toxicity at any level — Na/K-ATPase competition
— Worsening of ischemic events; hypokalemia post-MI increases mortality
— Atrial fibrillation more refractory to rate/rhythm control
— Progressive ascending weakness
— Respiratory muscle paralysis in severe cases (K⁺ <2.0) → intubation
— Rhabdomyolysis from impaired muscle perfusion (vasoconstriction is K⁺-dependent) — can paradoxically cause subsequent hyperkalemia
— Bulbar and ocular muscles spared (unlike Guillain-Barré)
— Nephrogenic diabetes insipidus — polyuria, polydipsia
— Chronic hypokalemia → hypokalemic nephropathy with interstitial fibrosis, tubular vacuolization, and CKD over years
— Increased renal ammoniagenesis → worsens hepatic encephalopathy in cirrhosis
— Metabolic alkalosis perpetuation (paradoxical aciduria classic finding)
— Ileus, constipation, gastric atony
— Worsening encephalopathy in cirrhosis
— Impaired insulin secretion → glucose intolerance
— Inhibits aldosterone secretion (negative feedback that fails when total body K⁺ depleted)
— Hyperkalemia from over-rapid IV repletion — especially in CKD
— Phlebitis and tissue necrosis from peripheral KCl >10 mEq/hr or concentrated infusions
— Esophageal ulceration from oral KCl tablets, especially in bed-bound or elderly patients
— Rebound hyperkalemia in periodic paralysis when total body K⁺ is normal
— Inadvertent bolus IV KCl — sentinel event, almost always fatal
Step 3 management: A patient on chronic furosemide develops new polyuria and serum K⁺ of 2.9 with osmolality findings suggesting nephrogenic DI — the correct first step is potassium repletion, not desmopressin; the DI is functional and reverses.
— K⁺ <3.0 with any symptoms
— K⁺ <2.5 regardless of symptoms
— Concomitant digoxin therapy with K⁺ <3.5
— Active ischemia, recent MI, or known long QT with K⁺ <3.5
— Hypokalemia + concurrent severe hypomagnesemia
— Failed outpatient repletion attempts
— Sustained ventricular arrhythmia or torsades
— Hemodynamic instability
— Respiratory muscle weakness/impending failure
— Need for IV KCl >10 mEq/hr (requires central line and continuous monitoring)
— Severe DKA with K⁺ <3.3
— Thyrotoxic periodic paralysis with paralysis
— Nephrology: unexplained renal K⁺ wasting, suspected Bartter/Gitelman/RTA, refractory hypokalemia, hypokalemia in CKD
— Endocrinology: suspected primary aldosteronism, Cushing, thyrotoxic periodic paralysis, pheochromocytoma
— Cardiology: arrhythmia management, digoxin toxicity
— Psychiatry/Eating disorders team: suspected bulimia, laxative or diuretic abuse
— Surgery: confirmed adrenal adenoma for adrenalectomy
— GI: chronic diarrhea workup, VIPoma evaluation
— K⁺ 3.0–3.4, asymptomatic, reliable patient
— Cause identified and modifiable (e.g., diuretic dose adjustment)
— No high-risk comorbidities (digoxin, recent MI, severe HF)
— Follow-up within 3–7 days for recheck
— K⁺ ≥3.5 sustained
— Mg²⁺ ≥2.0
— Cause addressed
— Medication reconciliation complete
— Follow-up labs scheduled within 1 week
— Patient understands warning signs (palpitations, weakness, syncope)
CCS pearl: On a CCS case, if you order IV KCl >10 mEq/hr you must also place a central line and document continuous cardiac monitoring — failure to sequence these is a tested patient-safety error.
— Often coexists; causes similar weakness, cramps, arrhythmias (torsades)
— Always check Mg in any hypokalemia workup
— Refractory hypokalemia without Mg correction is the classic exam trap
— Causes: PPIs (chronic use), loop/thiazide diuretics, alcohol, cisplatin, aminoglycosides, EGFR inhibitors, diarrhea
— Can cause similar tetany, paresthesias, QT prolongation
— Trousseau/Chvostek positive (not seen in hypokalemia)
— Often coexists with hypomagnesemia
— Weakness, rhabdomyolysis, respiratory muscle failure overlap
— Common in DKA recovery, refeeding, alcohol withdrawal
— Phosphate <1.0 mg/dL → IV repletion
— Confusion and weakness overlap
— SIADH, thiazide-induced hyponatremia often coexists with hypokalemia (especially elderly on HCTZ — classic stem)
— Metabolic alkalosis itself causes neuromuscular irritability via reduced ionized calcium
— Respiratory alkalosis transiently lowers K⁺ via shift
— Vomiting vs. surreptitious diuretic use vs. Gitelman: all give hypokalemia + alkalosis + normotension; distinguish by urine chloride (vomiting low, others high), urine calcium (Gitelman low), and urine diuretic screen
— Bartter vs. Gitelman: age of onset, urine calcium (Bartter high, Gitelman low), Mg (Gitelman low)
— Primary aldosteronism vs. Cushing vs. Liddle: ARR, dexamethasone suppression, family history and renin/aldosterone both low (Liddle)
— Type 1 vs. Type 2 RTA: urine pH (type 1 >5.5 always; type 2 variable, can acidify), bicarbonate level (lower in type 1), stones (type 1 yes, type 2 no), Fanconi features (type 2)
Key distinction: Hypokalemia + alkalosis + normotension + low urine calcium + hypomagnesemia = Gitelman; same picture with high urine calcium and normal Mg = Bartter; same picture with normal urine Ca/Mg and elevated urine diuretic screen = surreptitious diuretic abuse.
— Acute leukemia with WBC >100k → cells absorb K⁺ from plasma after blood draw at room temperature
— Repeat sample on ice and process immediately
— Insulin administration — therapeutic or endogenous (post-prandial glucose load)
— β2-agonists — albuterol nebs in asthma/COPD exacerbation (predictable 0.3–0.5 mEq/L drop)
— Catecholamine surge — MI, sepsis, alcohol withdrawal, theophylline toxicity
— Alkalosis — both metabolic and respiratory
— Hypokalemic periodic paralysis — familial channelopathy, often triggered by carbs/exercise/cold; thyrotoxic variant in Asian males
— Barium poisoning (industrial exposure)
— Vitamin B12 therapy for severe megaloblastic anemia (rapid cellular uptake)
— VIPoma (Verner-Morrison syndrome) — watery diarrhea, hypokalemia, achlorhydria (WDHA); rare but tested
— Zollinger-Ellison — diarrhea from gastric hypersecretion
— Villous adenoma of rectum — secretory diarrhea with K⁺ loss
— Ileostomy/colostomy high output
— Laxative abuse — alkalosis if vomiting present, acidosis if pure diarrhea; melanosis coli on colonoscopy
— Loop and thiazide diuretics
— Amphotericin B (distal RTA + Mg wasting)
— Aminoglycosides, cisplatin (Mg wasting → K wasting)
— Foscarnet
— High-dose penicillins (nafcillin, piperacillin — non-reabsorbable anions)
— Tenofovir → Fanconi syndrome
— Hyperthyroidism (mild K shifts)
— Cushing syndrome and ectopic ACTH
— Renin-secreting tumors
Board pearl: A young Asian man with sudden flaccid paralysis after a carb-heavy meal, K⁺ 1.8, and tachycardia with tremor → thyrotoxic hypokalemic periodic paralysis. Treatment is propranolol + cautious K⁺, then definitive thyroid management. Avoid aggressive K⁺ — rebound hyperkalemia is common.
— Diuretic-induced: lowest effective dose, add K-sparing agent, or switch class
— Vomiting/diarrhea: treat underlying disorder (gastroenteritis, IBD, eating disorder, hyperemesis)
— Primary aldosteronism: surgery for adenoma, MRA for hyperplasia
— Bartter/Gitelman: lifelong supplementation strategy
— Eating disorder: multidisciplinary care
— Oral KCl maintenance 20–40 mEq/day for ongoing losses (diuretic users, Gitelman); higher doses split BID/TID
— Spironolactone 12.5–50 mg/day or eplerenone 25–50 mg BID for HTN/HF/cirrhosis
— Amiloride 5–10 mg/day when spironolactone not tolerated or in Liddle syndrome
— ACE-I or ARB added to thiazide regimen reduces K⁺ losses
— Magnesium oxide 400 mg/day or Mg lactate for coexisting hypomagnesemia (caution: GI side effects, watch in CKD)
— High-K foods: bananas, oranges, potatoes, tomatoes, beans, spinach, avocado, dried fruits, dairy
— Average dietary K⁺: 40–100 mEq/day; can supplement deficit partially in mild cases
— Salt substitutes (KCl-based) — useful but caution in CKD or ACE-I/ARB users
— Avoid excessive caffeine and alcohol
— Pill burden reduction — combine HCTZ-triamterene or HCTZ-amiloride single tablets
— Medication reconciliation at every visit
— Pharmacist involvement in chronic disease management programs
— Hospital discharge: lab recheck within 1 week, medication list reconciled, primary care follow-up arranged
— Outpatient new diuretic start: BMP at 1–2 weeks, then 4–6 weeks, then every 6–12 months once stable
— Patients on ACE-I + diuretic + MRA combination: every 1–3 months
Step 3 management: When prescribing a thiazide for a hypertensive patient, the value-based, guideline-aligned move is to pair it with an ACE-I or ARB upfront rather than adding KCl supplements — fewer pills, better outcomes, fewer office visits for lab monitoring.
— Acute repletion in hospital: K⁺ every 2–4 hours during IV repletion, every 6–12 hours during oral repletion
— Post-discharge from acute hypokalemia: BMP within 3–7 days, then 2 weeks, then monthly until stable
— New diuretic prescription: BMP at 1–2 weeks, again at 4–6 weeks, then every 6–12 months when stable
— MRA initiation or up-titration: K⁺ and Cr at 1 week, 2–4 weeks, 3 months, then every 6 months
— Chronic diuretic users with stable K⁺: annual to biannual
— Primary aldosteronism on medical therapy: K⁺, BP, Cr every 3 months
— General target: K⁺ 4.0–5.0 for most patients with cardiovascular disease
— Heart failure on digoxin: K⁺ ≥4.0 strict
— Post-MI: K⁺ 4.0–5.0
— CKD on RAAS blockade: K⁺ ≤5.0 ceiling, tolerate down to 3.8
— Take oral KCl with full glass of water, upright posture, avoid lying down for 30 minutes
— Don't crush extended-release tablets
— Recognize warning signs: palpitations, profound weakness, syncope, severe cramps — call/seek care
— Hydration during illness with vomiting or diarrhea
— Avoid OTC laxatives unless directed
— Salt substitute caution in patients on RAAS blockade
— Address alcohol use disorder with formal counseling/treatment
— Eating disorder: outpatient team-based care, weight monitoring, K⁺ trending
— Athletes: hydration plan, oral rehydration with electrolytes in extreme heat
— Cardiac rehab after MI: ensures lab monitoring is built into the program
— Pill counts, pharmacy refill data
— Spot urine K⁺ to assess intake when adherence questioned
Board pearl: A diabetic on lisinopril, spironolactone, and HCTZ should have K⁺ and Cr checked 1 week after any dose change, then every 3 months. This triad has the tightest follow-up cadence on Step 3.
— Concentrated IV potassium chloride is on ISMP's High-Alert Medication List
— Never store concentrated KCl in patient care areas outside pharmacy (Joint Commission requirement)
— Only pre-mixed, diluted bags at bedside; pharmacy compounds higher concentrations
— Bolus IV KCl is essentially always fatal — labeled as a sentinel event when it occurs
— Independent double-check for IV KCl infusions in many institutions
— Smart pumps with dose error reduction software programmed for KCl limits
— Medication reconciliation errors at admission and discharge are the #1 cause of post-discharge hypokalemia events
— Diuretics added in hospital not communicated to outpatient provider → patient lost to follow-up → severe hypokalemia at home
— Mandatory: discharge summary specifying K⁺ at discharge, supplement dose, follow-up lab date
— Adrenalectomy for aldosteronoma: discuss alternative of lifelong MRA therapy, risk of recurrence, fertility/gynecomastia concerns for spironolactone vs. eplerenone
— Genetic testing for Gitelman/Bartter: counseling for family members, implications for life insurance
— Severe hypokalemia from bulimia may require involuntary hold if patient lacks capacity due to malnutrition and refuses life-saving care
— Multidisciplinary team approach, family involvement when appropriate
— Confidentiality balanced with safety; minors require additional parental notification considerations
— Not specifically required for hypokalemia, but eating disorder in a minor or elder with self-neglect may trigger child/adult protective services contact
— Suspected munchausen-by-proxy with surreptitious diuretic administration to a child is a reportable concern
— Cost of oral KCl supplements and generic K-sparing diuretics — choose affordable formulations
— Access to lab monitoring for patients without insurance: use patient assistance programs and home BP monitoring
Step 3 management: A hospitalized patient is found to have a bedside vial of concentrated KCl on the medication cart. The correct action is to remove the vial immediately, file a safety event report, and notify pharmacy — this is a Joint Commission violation regardless of whether harm occurred.
Board pearl: When a stem mentions PPI use plus diuretic use plus refractory hypokalemia, the answer is check and replace magnesium — chronic PPI use is a tested cause of hypomagnesemia.
— 24F with DKA, glucose 580, K⁺ 3.1, anion gap 28. Next step? → Hold insulin, give IV KCl until K⁺ >3.3, then start insulin. Tests recognition that insulin will drop K⁺ further.
— 58M on furosemide for HF, K⁺ persistently 3.0 despite 40 mEq KCl daily. Next step? → Check serum magnesium and replete. Distractor: increase KCl dose.
— 42F with HTN on three agents, K⁺ 3.2, alkalosis. Next step? → Plasma aldosterone-to-renin ratio. Followed by adrenal CT and AVS once confirmed.
— 24F with weakness, K⁺ 2.8, alkalosis, normotensive, urine Cl <20 → vomiting/bulimia. Look for dental erosions, Russell sign.
— Urine Cl >40, low urine Ca, low Mg → Gitelman.
— Urine Cl >40, high urine Ca → Bartter.
— Urine Cl >40, urine diuretic screen positive → surreptitious diuretic abuse.
— 28M, recent immigrant from East Asia, weakness after carb meal, K⁺ 1.9, tremor, tachycardia → thyrotoxic periodic paralysis. Treat with propranolol + cautious K⁺.
— Elderly HF patient on digoxin and HCTZ, nausea, vision changes, junctional bradycardia, K⁺ 3.1 → digoxin toxicity potentiated by hypokalemia. Next: digoxin level, replete K⁺ and Mg, consider digoxin-specific Fab if severe.
— Order to "give KCl 40 mEq IV bolus" → call provider, do not administer. Bolus KCl is fatal; max peripheral 10 mEq/hr.
— Patient with hypokalemia, hyperchloremic non-AG acidosis, urine pH 6.5 despite acidemia, kidney stones → type 1 (distal) RTA.
— Elderly on chronic omeprazole + HCTZ, K⁺ 2.9 refractory → hypomagnesemia from PPI.
— Cirrhotic with ascites on furosemide alone develops K⁺ 2.8 → add spironolactone, target 100:40 ratio.
CCS pearl: On CCS hypokalemia cases, advancing the clock without first ordering Mg, ECG, and continuous monitor is the most common cause of point loss — order them in the first screen.
Hypokalemia is a deficiency, a shift, or both — diagnose with serum Mg, urine K⁺, urine Cl, and acid-base status; replete with KCl (oral when possible, IV with limits when severe), always correct magnesium first, and always treat the underlying cause.
— Is it real? (rule out pseudohypokalemia)
— Is it a shift or a loss? (urine K⁺ <15 = extrarenal/shift; >15 = renal)
— What's the acid-base status? (alkalosis vs. acidosis splits the differential)
— What's the BP? (HTN points to mineralocorticoid excess; normotension to GI losses or tubulopathies)
— Oral KCl 20–40 mEq, 10 mEq raises K⁺ ~0.1
— IV KCl peripheral max 10 mEq/hr; central max 20 mEq/hr with telemetry
— Use saline, never dextrose-containing fluids
— Always check and replete Mg
— Recheck K⁺ every 2–4 hours during active repletion
— DKA: hold insulin if K⁺ <3.3
— Refractory hypokalemia: check Mg
— HTN + hypokalemia + alkalosis: ARR for primary aldosteronism
— Vomiting vs. diuretic vs. Gitelman: urine Cl and urine Ca split them
— Thyrotoxic periodic paralysis in Asian male: propranolol first
— Cirrhosis: spironolactone:furosemide 100:40
— Digoxin + low K + low Mg = arrhythmia trifecta — keep K⁺ ≥4.0
— Bolus IV KCl is a sentinel event — never order it
— New diuretic → BMP at 1–2 weeks
— Discharge documentation must include K⁺, Mg, supplement plan, and follow-up labs within 1 week
— Address root cause: medication review, eating disorder screening, endocrine workup when indicated
Step 3 management: The exam rewards clinicians who identify the cause, replete safely with attention to magnesium, monitor with appropriate cadence, and prevent recurrence through medication strategy — not those who simply give KCl and move on.