Potassium (Serum): What Your Result Means
Result guide · Electrolytes
Content last reviewed 2026-09-12 · Educational information — not medical advice
Quick answer
Potassium runs heart rhythm. Mild highs are usually lab artifact (hemolyzed draw); genuine highs and lows alike become dangerous quickly. Unexpected extremes get repeated before anyone acts.
What is Potassium (Serum)?
Intracellular potassium concentrations dwarf serum levels ~30-fold, making the measured 3.5–5.0 mmol/L a thin veneer over huge intracellular reserves. Insulin, acid-base status, and catecholamines shuttle potassium across membranes — explaining why diabetic ketoacidosis hides total-body depletion behind normal-looking serum values.
Typical reference interval: Approximately 3.5–5.0 mmol/L.. Laboratories differ — the interval printed on YOUR report always governs.
If your Potassium (Serum) is high
Common reasons Potassium (Serum) runs above the reference interval:
- Hemolysis in the tube — THE artifact — fist clenching, difficult draws, delayed processing lyse cells and spill potassium
- Kidney impairment — reduced excretion — the genuine pathophysiology
- ACE inhibitors/ARBs/spironolactone — predictable pharmacology, monitored combinations
- Acidosis — K+ shifts outward — DKA presents deceptively normal then crashes with insulin
- Tissue breakdown — rhabdomyolysis, tumor lysis, burns
- Type 4 RTA and adrenal insufficiency — aldosterone deficiency states
If your Potassium (Serum) is low
Common reasons Potassium (Serum) runs below the reference interval:
- Thiazide and loop diuretics — the routine outpatient cause
- Vomiting/diarrhea — GI losses plus renal compensation
- Insulin/glucose infusions — shift INTO cells — treats hyperkalemia precisely this way
- Alkalosis — same inward shift
- Magnesium depletion — refractory hypokalemia until magnesium corrected — the overlooked pairing
- Licorice, genetic tubulopathies — rare but real
Symptoms worth knowing
Muscle weakness, cramps, palpitations — then dangerous arrhythmias. ECG changes (peaked T-waves high; flattened T + U-waves low) track severity. Cardiac monitoring accompanies treatment of genuine extremes.
What usually happens next
Get your Potassium (Serum) checked
These lab tests measure Potassium (Serum) directly. Ordering online takes a few minutes and results arrive securely.
We may earn a commission when you order through partner links on the following pages. Educational information here never replaces advice from a qualified healthcare provider.
Panels that include this value
Potassium (Serum) appears as one line inside these broader panels — better value than ordering single markers alone:
Related result guides
Frequently asked questions about Potassium (Serum) results
Bananas — relevant?
One banana ≈ 400mg ≈ barely moves serum potassium in healthy kidneys. Dietary counseling matters in CKD, where multiple servings genuinely accumulate. Healthy people obsess over this unnecessarily.
My potassium was 6.2 but the repeat was 4.4 — which is real?
Almost certainly the second. Hemolysis artifact is common enough that guidelines mandate confirmation before treating asymptomatic modest highs.
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