A potassium blood test measures the amount of potassium in the fluid portion (serum) of your blood. Potassium is an electrolyte — an electrically charged mineral that helps control the balance of fluids and of acids and bases (pH) in your body, and that helps control muscle and nerve activity, among other important functions.
A provider may order it as part of a routine checkup (it is often included in a group of tests called an electrolyte panel) or to help monitor or diagnose conditions that can affect potassium levels, such as kidney disease, high blood pressure, heart disease, diabetes, or adrenal gland disorders. It may also be ordered for people taking medicines that can affect potassium levels, or who have symptoms possibly linked to high potassium (such as arrhythmia, fatigue, muscle weakness, nausea, or numbness/tingling) or low potassium (such as irregular heartbeat, muscle cramps, weak or twitching muscles, fatigue, nausea, or constipation).
MedlinePlus gives a general normal range of about 3.7 to 5.2 milliequivalents per liter (mEq/L), or 3.70 to 5.20 millimoles per liter (mmol/L). This is a general reference only. Normal ranges may vary slightly among different laboratories and can also differ by the method used and by a person's age and sex. The reference range printed on your own lab report is the authoritative figure for your result, and a single value outside a general range is not, by itself, a diagnosis.
A higher-than-normal potassium level (hyperkalemia) is a general finding that can be seen with many different situations and is not a diagnosis on its own. According to MedlinePlus, it may be associated with things such as kidney insufficiency or failure, Addison disease, hypoaldosteronism, crushed-tissue injury, red blood cell destruction, blood transfusion, hyperkalemic periodic paralysis, metabolic or respiratory acidosis, a high dietary intake of potassium, or the effect of certain medicines (such as ACE inhibitors, ARBs, potassium-sparing diuretics, or beta blockers). This is not a complete list, and results are interpreted in context by a clinician.
A lower-than-normal potassium level (hypokalemia) is likewise a general finding with many possible associations, not a diagnosis. According to MedlinePlus, it may be seen with things such as acute or chronic diarrhea or vomiting; the effect of diuretics (for example hydrochlorothiazide, furosemide, torsemide, or indapamide); hyperaldosteronism or Cushing syndrome; renal artery stenosis or renal tubular acidosis; hypokalemic periodic paralysis; or insufficient dietary potassium. This is not a complete list, and only a clinician can interpret what a given result means for a particular person. This page is general health information, not medical advice, and it does not replace the reference ranges on your own lab report or the judgment of your clinician, who interprets any result together with your history, symptoms, medicines, and other tests.
Reference ranges vary by laboratory, age, sex, and method — the range on your own report is what applies to you. A single value out of range doesn’t confirm any condition; your clinician interprets it alongside your symptoms, history, and other results. This page is general information, not medical advice.
General reference, not medical advice, and not a substitute for your clinician. Lab reference ranges and interpretation depend on the laboratory and on your individual situation — discuss your results with a licensed healthcare professional.