A high potassium in a stable outpatient with chronic kidney disease should prompt one question before any treatment decision: how did the sample get to the laboratory. Pseudohyperkalaemia from a difficult venepuncture, a fist clenched during sampling, a small-gauge needle, a delayed or refrigerated sample, or a sample taken above a running drip will all produce a number that looks like a reason to stop a renin-angiotensin blocker.
And stopping it is the harm. A patient taken off an ACE inhibitor or ARB after one raised result frequently never goes back on, and the drug that was slowing their disease is lost to a laboratory artefact. Before acting, ask when and how the sample was taken and whether there was any difficulty, check whether haemolysis was flagged, and repeat it properly — same-day if the patient is unwell, at the next visit if they are not.
Where the result is genuine, treat the potassium rather than reflexively withdrawing the drug: review dietary sources, check for a non-steroidal or a potassium-sparing diuretic nobody recorded, consider a binder, and reduce the dose before stopping it.
- Ask how the sample was taken before acting on an isolated high potassium
- Check whether haemolysis was flagged on the report
- Repeat properly before withdrawing a renin-angiotensin blocker
- Where the result is real, look for the added drug or the dietary change before stopping treatment
Why it matters
A drug stopped on a spurious result is rarely restarted, and the patient loses the treatment slowing their disease.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for nephrology, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free