Lab test glossary · Other
Potassium: what it means
Also known as: K
Potassium is an electrolyte vital for nerve and heart function; both high and low levels can affect heart rhythm.
What it measures
Potassium is an electrolyte that your nerves and muscles — including the heart — depend on. Levels are kept in a tight range by the kidneys and hormones, and both ends of abnormal can affect heart rhythm, which is why it's watched closely.
Typical range
Often roughly 3.5–5.0 mmol/L.
Reference ranges differ between labs and are printed on your own report — always read your result against that range, not a general one.
What a high result can mean
- Reduced kidney function
- Certain blood-pressure and other medications
- A hemolyzed (damaged) sample can falsely raise it
A high value is a starting point for a conversation, not a diagnosis — many causes are benign or temporary.
What a low result can mean
- Diuretics, vomiting, or diarrhea
- Some hormonal conditions
Why the trend matters
Potassium is tightly regulated, so a genuine trend outside the range — not a one-off from a difficult draw — is what matters.
When to talk to your doctor
A potassium clearly outside the range should be reviewed with your doctor promptly, particularly on kidney or blood-pressure medications.
This page is general education about a common lab test — it isn’t medical advice and can’t interpret your specific result. What a value means depends on your history, symptoms, and the rest of your labs, which is a conversation for you and your clinician.