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COMPREHENSIVE METABOLIC PANEL (CMP)
Also printed as: K · Serum potassium
Educational only — not medical advice.
Potassium is the main electrolyte inside your cells, and the small amount in your bloodstream is what the test measures. It helps nerves fire and muscles contract, including your heart muscle. Your kidneys do most of the work keeping it in a narrow band.
Potassium is one of the few markers where the lab itself is a common source of variation, so clinicians treat unexpected values with healthy skepticism and often repeat them before reading anything into the result.
TYPICAL ADULT RANGE
Many labs report roughly 3.5–5.2 mmol/L for adults. Ranges vary by lab and by collection method. Reported in mmol/L.
Reference ranges vary by lab, by method, and by age and sex. Always read your own result against the range printed on your report.
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Mildly low potassium has everyday explanations: diuretics, a bout of vomiting or diarrhea, heavy sweating, or simply a diet light on fruits and vegetables. Some blood-pressure and asthma medications shift it too. Because low potassium can affect muscle and heart rhythm when it is significant, your doctor will want to know about persistent lows, muscle cramps, or unusual weakness — but a single mildly low value is common and usually gets rechecked first.
The single most common reason for a high potassium result is the draw itself. If red cells break during collection or the sample sits too long, potassium leaks out and the reported value rises even though your actual level is fine — labs call this hemolysis and often note it on the report. Clenching your fist during the draw does the same thing. Kidney function and certain blood-pressure medications also raise it genuinely. Because of that, an unexpected high potassium is almost always repeated before anyone interprets it, and that repeat is the number worth discussing with your doctor.
Your doctor is the one who can read this number against your history, symptoms, and medications.
Educational only — not medical advice. Lab results only mean something alongside your history, symptoms, medications, and the rest of your panel. Bring questions to your doctor; they are the one who can interpret your results for you.
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