What this test measures
Potassium is the major intracellular cation — about 98% of the body's potassium is inside cells, only 2% in extracellular fluid. The narrow serum range (3.5–5.0 mEq/L) is tightly defended because even small changes affect nerve conduction, muscle contraction and the heart's electrical activity.
Potassium balance is maintained by intake (diet), excretion (mainly kidneys — about 90%), and shifts between intracellular and extracellular compartments (driven by insulin, catecholamines, acid-base status, and aldosterone). Hyperkalaemia is one of the few electrolyte derangements that can cause sudden cardiac death — it deserves prompt action.
Why it matters
In India, potassium abnormalities are common and clinically important. Low potassium is seen with diuretic use (very common in hypertension and heart failure), severe diarrhoea / vomiting, hyperaldosteronism, magnesium deficiency, and tropical conditions like Vibrio cholerae enteritis. High potassium is the dangerous one — common with CKD (especially eGFR <45), ACE inhibitors / ARBs / spironolactone, severe diabetes, rhabdomyolysis, and tumour lysis. Hyperkalaemia >6 mEq/L can cause peaked T waves, widened QRS and ventricular arrhythmia.
Potassium is part of every electrolyte panel and is the most-watched lab value in hospitalised patients on the wards.
How to prepare
No fasting required. Avoid prolonged fist-clenching and tight tourniquet — both falsely raise potassium (pseudohyperkalaemia). The sample must be processed promptly — delayed processing and haemolysis can spuriously raise potassium by 0.5–1.0 mEq/L. Mention all medications, especially diuretics, ACE inhibitors / ARBs, spironolactone, potassium supplements.
Markers & reference ranges
Reference ranges below are typical adult values. Your lab's reported range may differ slightly based on the assay platform and patient demographics — always read your report against the range printed on it.
| Marker | Normal range | If low | If high |
|---|---|---|---|
| Potassium (mEq/L)[1][2] | 3.5 – 5.0 | Hypokalaemia. <3.5 — muscle weakness, cramps, palpitations, ECG changes. <2.5 — life-threatening: paralysis, arrhythmia. Causes — diuretics (loop, thiazide), vomiting, diarrhoea, low intake, magnesium deficiency, hyperaldosteronism (primary or secondary), renal tubular acidosis (type 1, 2), insulin / beta-agonist treatment (shift into cells), Cushing's syndrome. | Hyperkalaemia. >5.0 — first check for pseudohyperkalaemia (haemolysis, prolonged tourniquet). >6.0 — significant; check ECG, hold ACEi/ARB/spironolactone. >6.5 with ECG changes — emergency: calcium gluconate (membrane stabilisation), insulin + dextrose (shift), salbutamol, sodium bicarbonate if acidotic, potassium binders, dialysis if severe. Causes — CKD (especially eGFR <45), ACEi / ARB / spironolactone / heparin / NSAID, severe acidosis, rhabdomyolysis, tumour lysis, severe tissue injury, Addison's disease. |
Potassium ranges and what they mean
| Potassium (mEq/L) | Status | Risk | Action |
|---|---|---|---|
| < 2.5 | Severe hypokalaemia | Paralysis, arrhythmia | IV potassium under cardiac monitoring + Mg replacement |
| 2.5 – 3.4 | Mild–moderate hypokalaemia | Cramps, weakness, ectopy | Oral / IV potassium; check magnesium; review diuretic |
| 3.5 – 5.0 | Normal | No risk | No action |
| 5.1 – 5.9 | Mild hyperkalaemia | Often asymptomatic; rule out pseudohyperkalaemia | Repeat with proper technique; review ACEi/ARB/K-sparing drug; reduce dietary K |
| 6.0 – 6.4 | Moderate hyperkalaemia | ECG changes possible | Stop offending drug; ECG; possibly insulin + dextrose; potassium binder |
| ≥ 6.5 with ECG changes | Severe — emergency | Ventricular arrhythmia, cardiac arrest | IV calcium, insulin + dextrose, salbutamol, dialysis if needed |
Frequently asked questions
My potassium came back 5.4. Should I worry?
Mild hyperkalaemia is sometimes from sample handling (haemolysis, delay, tight tourniquet) — confirm with a fresh, properly drawn sample. If genuinely raised, review medications (ACE inhibitor, ARB, spironolactone, potassium supplements, NSAIDs) and kidney function. >6.0 needs prompt action.
Do I need to fast?
No fasting required. Avoid prolonged fist clenching and tight tourniquet during sample collection — they falsely raise potassium.
Why does my potassium drop on diuretics?
Loop and thiazide diuretics increase urinary potassium loss. Potassium-sparing diuretics (spironolactone, eplerenone, amiloride) do the opposite and can cause hyperkalaemia. Doctors choose the diuretic and monitor accordingly.
What foods are high in potassium?
Bananas, oranges, tomatoes, potatoes, sweet potatoes, coconut water, spinach, dates, beans, dal, and salt substitutes (which use potassium chloride). CKD patients with high potassium are advised to limit these.
My potassium is 3.2. How do I correct it?
Mild hypokalaemia — oral potassium chloride or potassium-rich diet, plus addressing the cause (diuretic dose adjustment, magnesium replacement). Severe (<2.5) or symptomatic — IV potassium with cardiac monitoring.
Can hyperkalaemia cause cardiac arrest?
Yes. Potassium >6.5 can cause peaked T waves, widened QRS, sine-wave pattern and ventricular fibrillation. It is one of the few electrolyte derangements that needs immediate emergency action.
Are ACE inhibitors safe in CKD?
They are recommended in CKD because they slow progression — but they raise potassium. Most patients tolerate them well with regular monitoring. The drug is stopped or reduced only if potassium consistently exceeds 5.5 despite dietary measures.
Related Kidney / Electrolytes tests
Tests commonly ordered alongside POTASSIUM, or that help interpret an unexpected result.
Sources & references
- NIH MedlinePlus — Potassium Blood Test · accessed 2026-05-30T00:00:00.000Z
- NCBI StatPearls — Hyperkalemia · accessed 2026-05-30T00:00:00.000Z
- KDIGO 2024 CKD Guideline · accessed 2026-05-30T00:00:00.000Z
Book with Zelnoo
Get your POTASSIUM test done at home — transparent prices, NABL-accredited labs.
Zelnoo lets you compare diagnostic test prices across NABL-accredited labs in Mumbai & Thane, book a free home phlebotomist visit, and receive digital reports in 24–48 hours into a consent-first report vault. No subscriptions, no membership fees — pay only for the test you book.
Book POTASSIUM now