Potassium
Primary intracellular mineral for heart rhythm, blood pressure, and muscle contraction
Also known as
Definition
Potassium is the most important intracellular cation and plays a central role in regulating the resting membrane potential, heart rhythm, muscle contraction, nerve impulse conduction, and blood pressure. The kidneys regulate potassium levels precisely. Hypokalemia and hyperkalemia can cause life-threatening cardiac arrhythmias and require rapid intervention.
| Parameter | Value |
|---|---|
| Unit | mmol/l (mEq/l) |
| Reference Range | 3.5–5.0 mmol/l |
| Optimal Range (lab2go) | 4.0–4.8 mmol/l (lab2go Optimum Zone; low end of range increases arrhythmia risk) |
↓ What a low value means
Hypokalemia (< 3.5 mmol/l) arises from diuretics, vomiting, diarrhea, laxative abuse, primary hyperaldosteronism, or inadequate intake. Symptoms: muscle weakness, cramps, cardiac arrhythmias (prolonged QT interval), constipation, fatigue. Life-threatening below 2.5 mmol/l.
↑ What a high value means
Hyperkalemia (> 5.0 mmol/l) occurs with kidney insufficiency, hypoaldosteronism, ACE inhibitors/ARBs, potassium-sparing diuretics, extensive hemolysis, or massive muscle breakdown (rhabdomyolysis). Cardiac risk: dangerous arrhythmias (ventricular fibrillation) at > 6.5 mmol/l.
✓ How to optimize this marker
Potassium-rich sources: bananas, avocados, spinach, potatoes, legumes, dried fruits, tomatoes. Daily requirement: 3500 mg (EFSA) to 4700 mg (US). With diuretic therapy: dietary optimization or supplementation (under medical supervision). Magnesium repletion is important (hypomagnesemia perpetuates hypokalemia).
When to test
In every routine blood panel; mandatory with diuretic therapy, heart disease, kidney insufficiency, diabetes, ACE inhibitor/ARB use, vomiting/diarrhea, eating disorders, or peak athletic training. Exclude pseudohyperkalemia from hemolysis of the blood sample.
Frequently asked questions
Why is potassium so critical for the heart? +
Potassium determines the resting membrane potential of cardiac muscle cells. Too little potassium (< 3.5 mmol/l) lowers the resting potential and makes heart muscle cells hyperexcitable — the risk of ventricular arrhythmias rises. Too much potassium permanently depolarizes heart muscle cells and can cause cardiac arrest.
Does potassium really help with high blood pressure? +
Yes. Potassium increases sodium excretion by the kidneys and acts as a vasodilator. DASH diet studies show that increased potassium intake can lower systolic blood pressure by 3–6 mmHg. The WHO recommends > 3500 mg potassium daily as a cardiovascular protective measure.
Can exercise lead to potassium deficiency? +
Intense exercise increases potassium loss through sweat minimally, but can transiently alter levels through aldosterone activation and redistribution between intra- and extracellular compartments. Chronic potassium deficiency is rare in endurance athletes with a balanced diet. With cramps, also consider magnesium deficiency.
Sources
Last Reviewed: May 28, 2026 · sina
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.