Potassium is a mineral that keeps your heart rhythm, muscles and nerves working properly.
- Normal range (adults)
- 3.5–5 mmol/L
- Sample
- Blood
- Fasting
- Not usually needed
- Also called
- K, Serum Potassium, S.Potassium, K+, Potassium Serum
Potassium normal range
| Group | mmol/LSame unit in all countries |
|---|---|
| Adults | 3.5–5 |
Ranges vary slightly between laboratories. The range printed on your own report is the one to go by.
Why is the Potassium test done?
It is part of the electrolyte panel and is checked often in people with kidney disease or on blood pressure and heart medicines.
What does a high Potassium level mean?
High potassium (hyperkalemia) can disturb the heart rhythm and becomes dangerous above about 6.0 mmol/L.
Common causes
- Kidney disease
- Medicines such as ACE inhibitors, ARBs, spironolactone and potassium supplements
- Uncontrolled diabetes
- Sample damage during collection (a falsely high result is common)
Diet and lifestyle tips
- If your doctor advises, limit high-potassium foods: bananas, dates, dried fruit, potatoes, tomatoes, oranges, coconut water
- Avoid potassium-based salt substitutes
- Do not take potassium supplements unless prescribed
What does a low Potassium level mean?
Low potassium (hypokalemia) can cause muscle weakness, cramps, constipation and irregular heartbeat.
Common causes
- Vomiting or diarrhoea
- Water pills (diuretics)
- Excess laxative use
- Low magnesium
Diet and lifestyle tips
- Eat potassium-rich foods: bananas, dates, oranges, potatoes, spinach, beans, yogurt, coconut water
- Eat magnesium sources too: nuts, seeds, whole grains
When should you see a doctor?
Seek urgent care for potassium below 3.0 or above 6.0 mmol/L, or for palpitations or muscle weakness.
Last updated
This page is for general education and is not a diagnosis. Normal ranges differ between laboratories, so always compare your result with the reference range printed on your own report, and discuss abnormal results with your doctor.