BLOOD TEST · SMART CARE POLYCLINIC, DEIRA
Potassium explained
The electrolyte that matters most to heart rhythm — acted on the same day when far outside range.
What the Potassium test measures
A mineral held mostly inside cells, governing the electrical signalling of nerves, muscle and the heart. The blood level is kept in a tight range, and both directions matter. A mildly raised result is often repeated before anything is concluded, because red cells breaking down after the sample is taken can push the number up on their own.1
Reported as part of Kidney Function & Electrolytes.
What the result tells you
The result most likely to prompt a same-day call
A high potassium interferes with the heart's electrical conduction and can cause dangerous rhythms with little or no warning.
The doctor's first question: is it real?
Potassium leaks from red cells if a sample is difficult, delayed or shaken, and clenching the fist raises it. An unexpected high in a well person is repeated first.
When genuinely high
Usually reduced kidney function plus the medicines that conserve potassium — ACE inhibitors, ARBs, certain water tablets — often in combination.
If it's low
Generally losses: water tablets, vomiting or prolonged diarrhoea. It also will not correct while magnesium is low, so the two are read together.
How to prepare
- Fasting
- Not needed
- Best time
- Any time, usually with the rest of the panel
- Avoid before
- Heavy exercise beforehand
- Worth knowing
- Do not clench or pump your fist during the draw — it raises the reading artificially and can force a repeat.
What can move the result
A result outside the usual range does not on its own mean something is wrong. These are the everyday explanations a doctor considers first.
Frequently asked questions
A mineral held mostly inside cells, governing the electrical signalling of nerves, muscle and the heart. The blood level is kept in a tight range, and both directions matter. A mildly raised result is often repeated before anything is concluded, because red cells breaking down after the sample is taken can push the number up on their own. The result most likely to prompt a same-day call: A high potassium interferes with the heart's electrical conduction and can cause dangerous rhythms with little or no warning.
Fasting: Not needed. Best time: Any time, usually with the rest of the panel. Avoid beforehand: Heavy exercise beforehand. Do not clench or pump your fist during the draw — it raises the reading artificially and can force a repeat.
Commonly: a difficult or delayed blood sample, which raises it falsely; clenching the fist during the draw; aCE inhibitors, ARBs and potassium-sparing water tablets; reduced kidney function; vomiting, diarrhoea and low magnesium, which lower it. A single result is not a diagnosis. Values are read against the laboratory's own reference range and alongside your history, your symptoms and the rest of the panel — which is why every package includes a doctor to go through them with you.
At Smart Care Polyclinic, 29 Doha Centre, Al Maktoum Rd, Deira, Dubai. Walk in during opening hours or call +971 (0)4 379 3562.
Sources
Written from current guidance and reviewed 31 August 2026.
Sources cited above
- Simon LV, Rout P. Hyperkalemia. StatPearls, StatPearls Publishing. 2025. PMID 29261936What a raised potassium means clinically, and why a mildly raised result is often repeated — a sample can read high if red cells break down after the draw.
Sources are listed for the specific statements they support. They are published research and guidance, not a substitute for a consultation — what applies to you is decided by a doctor who has assessed you.
- Potassium blood testMedlinePlus, US National Library of Medicine
- Chronic kidney disease and potassium managementKidney Disease: Improving Global Outcomes (KDIGO)
- Blood testsNHS