Normal Potassium — FRCA Primary MCQ
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Correct answer: A — 3.5 to 5.0 mmol/L
The best answer is “3.5 to 5.0 mmol/L”. An adult potassium concentration around 3.5 to 5.0 mmol/L is conventionally normal, although local laboratory reference ranges vary slightly. Values below this range indicate hypokalaemia and values above it indicate hyperkalaemia, with urgency determined by severity, ECG changes and clinical context.
Reference: Resuscitation Council UK, Special circumstances guidelines: https://www.resus.org.uk/professional-library/2025-resuscitation-guidelines/special-circumstances-guidelines