Potassium blood test: what it means
What it measures
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.
Why it’s ordered
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).
General reference range
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.
If it’s high
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.
If it’s low
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.
A result is not a diagnosis
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.
Medicines that can move this result
ACE inhibitors lower aldosterone, the hormone that tells the kidney to flush potassium into the urine, so more potassium stays in the blood. The label puts this at 2.2% of hypertension patients and 4.8% of heart-failure patients.
Source ↗Blocking the angiotensin II receptor lowers aldosterone the same way an ACE inhibitor does, so the kidney holds on to potassium instead of excreting it.
Source ↗It blocks aldosterone directly at the kidney — a "potassium-sparing" diuretic, meaning water and sodium leave in the urine but potassium is held back. High potassium is common enough with it that the drug is contraindicated in anyone already hyperkalemic.
Source ↗Trimethoprim (the second half of Bactrim/co-trimoxazole) blocks a sodium channel in the kidney tubule much as a potassium-sparing diuretic does, so less potassium is passed into the urine. The label documents this most clearly at the high doses used for P. jirovecii pneumonia, but notes ordinary doses can do it too in people with reduced kidney function or on other potassium-raising drugs.
Source ↗This thiazide "water pill" blocks sodium reabsorption partway along the kidney tubule, so more sodium reaches the segment downstream where the kidney swaps it for potassium — and that potassium leaves in the urine.
Source ↗A loop diuretic drives a large volume of urine and potassium is washed out with it — the heavier the diuresis, the bigger the drop. Low dietary intake, cirrhosis, steroids or laxatives make it worse.
Source ↗Beta-agonists move potassium out of the blood and into cells ("intracellular shunting"), so the measured blood level dips even though total body potassium has not changed. The effect is usually short-lived after a treatment.
Source ↗Insulin drives potassium from the bloodstream into cells, so the measured blood level falls — the same effect is used deliberately, with glucose, to treat dangerously high potassium.
Source ↗Do not stop a prescribed medicine over a lab number. These are recognised associations, not a finding about your result — your value may have nothing to do with any medicine you take, and the list is not complete. Bring it to whoever prescribed the drug; they can weigh it against why you are taking it.
Frequently asked
- What does the Potassium blood test measure?
- 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.
- What is a normal Potassium blood test range?
- 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.
- What does a high result mean?
- 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.
- What does a low result mean?
- 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.
Other lab tests
Sources
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.