Potassium · high result
High potassium (hyperkalemia): what it means, causes and when it is urgent
Short answer
High potassium (hyperkalemia) — above about 5.0–5.2 mmol/L — is frequently a sample artifact: a tight tourniquet, fist clenching, hemolysis (red cells breaking in the tube) or a delay before processing all release potassium and produce a falsely high result, so an unexpected value in someone who feels well is repeated before anything else. True hyperkalemia comes from reduced kidney function, medications that hold potassium (ACE inhibitors, ARBs, spironolactone, potassium supplements, NSAIDs, trimethoprim), uncontrolled diabetes, adrenal insufficiency and tissue breakdown. Potassium affects the heart's rhythm directly, so above about 6.0 mmol/L — or any elevation with weakness, palpitations or an irregular pulse — is treated as an emergency.
Medically reviewed by Youmna DiStefano, MD · Last reviewed November 2026
When does this result need same-day care?
- Potassium above 6.0 mmol/L, or any elevation with palpitations, weakness or an irregular pulse — emergency care; this can stop the heart
- Potassium above 5.5 mmol/L in someone with kidney disease, on an ACE inhibitor/ARB/spironolactone, or with diabetes — same-day care
- A high potassium after extreme exercise or injury with dark urine (rhabdomyolysis) — emergency care
What is the normal range for Potassium?
- age 18+: 3.50 – 5.00 mmol/L
Can reflect kidney issues, certain medications, or sample handling issues. Severe elevations can affect heart rhythm.
Full reference table, citations and testing options: Potassium biomarker page.
What are the common causes of high Potassium?
- Sample artifact — hemolysis, fist clenching during the draw, a tourniquet on too long, a sample left standing or chilled before processing, very high platelet or white cell counts; the most common cause of an unexpected high value
- Reduced kidney function — acute kidney injury or chronic kidney disease, especially once eGFR is below about 30
- Medications — ACE inhibitors, ARBs, spironolactone and eplerenone, amiloride, potassium supplements and salt substitutes, NSAIDs, trimethoprim, heparin, some immunosuppressants
- Uncontrolled diabetes and insulin deficiency — insulin moves potassium into cells; without it potassium stays in the blood (and diabetic kidney disease often adds a low-renin state)
- Adrenal insufficiency (Addison's) and low aldosterone states
- Tissue breakdown — rhabdomyolysis after extreme exercise or crush injury, hemolysis, tumor lysis, burns, large bruises
- Acidosis — hydrogen ions move into cells and potassium moves out
- Rare inherited conditions (hyperkalemic periodic paralysis) and a high-potassium diet only in the presence of kidney disease or the medications above
What symptoms go with high Potassium?
- Usually none until the level is well above range
- Muscle weakness and fatigue, sometimes starting in the legs
- Nausea, tingling
- Palpitations, a slow or irregular heartbeat, and — at high levels — cardiac arrest; the danger is electrical and can occur without warning symptoms
What do clinicians usually check next?
- Repeat with a careful draw — no fist clenching, tourniquet released promptly, sample processed quickly — and ask the lab whether the first sample was hemolyzed
- Creatinine and eGFR, glucose, bicarbonate (CO2) and a full metabolic panel
- Medication review, including over-the-counter NSAIDs, potassium-containing salt substitutes and supplements
- An ECG when potassium is above about 6.0 mmol/L or there are any symptoms — the ECG shows how urgent it is
- Morning cortisol and aldosterone/renin when kidney function and medications do not explain it
- CK and urinalysis when muscle injury is possible; a blood smear or CBC when counts are very high
- Treatment of the cause — dose adjustments, dietary potassium limits when kidney function is reduced, potassium binders in chronic kidney disease — under a clinician
Follow-up tests available at TestWell: CBC with Differential Test ($17.99), Cortisol Test (AM) ($26.49), Aldosterone Test ($61.99), Glucose Test ($14.99).
How do you recheck Potassium?
Prices are cash-pay; every order adds one $6 lab processing fee. Physician authorization is included; no insurance or referral needed.
| Test or panel | Type | Price | Fasting | Results |
|---|---|---|---|---|
| Basic Metabolic Panel | Test · 8 biomarkers | $17.99 | Yes | 1–3 business days |
Common questions
Why would my potassium be high if I feel fine?
Most often the sample: clenching, a tourniquet on too long, or red cells breaking during processing release potassium. A calm repeat draw usually normalizes it.
What is a high potassium level?
Above the lab's upper limit, usually 5.0–5.2 mmol/L. 5.1–5.5 is mild and often artifact; 5.5–6.0 moderate; above 6.0 severe and an emergency because of the heart. The ECG, not just the number, guides how fast it is treated.
What causes high potassium?
After sample artifact: reduced kidney function, medications that retain potassium (ACE inhibitors, ARBs, spironolactone, supplements, NSAIDs, trimethoprim), uncontrolled diabetes, adrenal insufficiency and tissue breakdown. Diet alone almost never causes it in someone with normal kidneys.
Can bananas or diet cause high potassium?
Not with normal kidney function — the kidneys excrete what you eat. With chronic kidney disease, or on potassium-retaining medications, high-potassium foods (bananas, potatoes, tomatoes, oranges, salt substitutes) do add up and a dietary limit is part of treatment.
Is a potassium of 5.3 dangerous?
On its own, rarely — it is a mild elevation and frequently a hemolyzed or clenched-fist sample. Repeat it carefully. If it is real, the question is why: kidney function, medications and glucose answer it in most people, and treatment is adjusting those rather than anything urgent.
How do you lower high potassium?
Mild, real hyperkalemia: stop or reduce the responsible medication, limit dietary potassium if kidney function is low, treat high glucose, sometimes a diuretic or a potassium binder. Severe hyperkalemia is treated in hospital with calcium to protect the heart, insulin and glucose to shift potassium into cells, and removal by binders or dialysis.
Educational content, not a diagnosis. Lab results are one input; a clinician interprets them with your history and exam.