Low blood potassium

Clinically: Hypokalaemia · also low potassium, potassium deficiency, potassium deficiency disease

electrolyte ICD-10 E87.6 MONDO MONDO:0003019 unverified

This describes what this condition typically looks like. It is not a diagnosis and cannot tell you whether you have it -- patterns overlap, results vary between labs, and the same numbers mean different things in different people. Diagnosis usually rests on Potassium, interpreted alongside symptoms and history rather than read off a report.

unverified These explanations are written to be easy to read and have not yet been checked against a source. The ranges and measurement notes on this page show theirs.

definition unverified

Potassium in the blood has fallen below normal. Common causes are fluid lost through vomiting or diarrhoea, and water tablets.

Serum potassium concentration below the normal range (3.5-5.0 mEq/L), with levels below 2.5 mEq/L defining severe, life-threatening hypokalaemia. It usually results from increased potassium excretion or an intracellular shift of potassium, and less commonly from reduced intake.

caveats unverified

This matters because your heart rhythm needs potassium to stay in a narrow range. Magnesium is often low at the same time. Topping up potassium rarely works until the magnesium is fixed as well.

No clinical version written yet.

The typical lab pattern

What the diagnosis rests on

The results a diagnosis is actually made on.

Potassium

low

—

Defined by a serum potassium below the normal range (below 3.5 mEq/L); below 2.5 mEq/L is severe.

Consistent with it

Fits the picture, but not enough on its own.

Magnesium	low	—	Low magnesium comes with more than half of significant cases, and must be corrected for potassium treatment to work.
Carbon dioxide, total	either	—	Bicarbonate is part of the first-line work-up. Some causes come with a high level (metabolic alkalosis), others with a low one (metabolic acidosis).

How it usually feels

Frequencies say how often a symptom accompanies this condition — not the other way round. Most people with any of these symptoms do not have this.