What initial investigations should I perform for a patient with suspected hyperkalaemia?

Initial investigations for suspected hyperkalaemia should include:

• Serum potassium measurement to confirm hyperkalaemia and assess severity.
• Repeat serum potassium to exclude spurious hyperkalaemia and monitor trends.
• Serum creatinine and urea to assess kidney function and detect acute kidney injury, as impaired renal excretion is a common cause of hyperkalaemia.
• Electrolytes including sodium, bicarbonate, and magnesium, since electrolyte imbalances often coexist and influence potassium levels.
• Electrocardiogram (ECG) to detect cardiac conduction abnormalities caused by hyperkalaemia.
• Review of medications that may contribute to hyperkalaemia, such as potassium-sparing diuretics, ACE inhibitors, ARBs, and NSAIDs.
• Assessment of volume status and clinical signs of hypovolaemia or fluid overload.

Additional investigations may be guided by clinical context, such as blood glucose for diabetic emergencies or adrenal function tests if adrenal insufficiency is suspected.

These investigations help identify the cause, assess severity, and guide urgent management to prevent life-threatening complications.

References: NICE CKS, NICE NG148, NICE NG243