GPAtlas🧭 When to suspect
Hyperkalaemia is most often a laboratory finding rather than a clinical one.
• There is no single agreed definition, but UK guidance treats a serum potassium > 5.5 mmol/L as the threshold for action.
• The majority of cases are asymptomatic and picked up on routine or drug-monitoring bloods.
When symptoms occur they are non-specific:
• Muscle weakness
• Paraesthesia
• Palpitations
• General malaise
The danger is that severe hyperkalaemia can precipitate fatal arrhythmia or cardiac arrest with little warning.
• First confirm the result is genuine (artefactual rises are common).
• Then risk-stratify by the potassium level.
Management is driven almost entirely by the number and the clinical context.
Suspect and actively monitor in:
• Chronic kidney disease (CKD)
• Diabetes
• Heart failure
• Acute kidney injury (AKI)
• Addison's disease
• Anyone taking a drug that raises potassium – particularly renin–angiotensin–aldosterone system inhibitors (RAASi): angiotensin-converting enzyme inhibitors (ACE inhibitors), angiotensin receptor blockers (ARBs) and mineralocorticoid receptor antagonists (MRAs)
| Serum potassium | Classification | Action |
|---|---|---|
| ≤ 5.5 mmol/L | Within reference range | • No action if well • Routine monitoring per risk |
| 5.5–5.9 mmol/L | Mild | • Address reversible causes • Repeat within ~1 week |
| 6.0–6.4 mmol/L | Moderate | Usually managed in community if well: ECG, treat causes, repeat within 1 day |
| ≥ 6.5 mmol/L | Severe | Immediate admission regardless of symptoms or ECG |
Source: UK Kidney Association (2023) · NICE TA1148
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