How to recognize high potassium on an ECG
Other platforms explain it with text and video. In VMS you practice it on the patient.
High potassium can stop the heart with little warning. ECG changes mean the heart is already affected and treatment must start now.
Step by step
Look at the T waves
The earliest sign is tall, narrow, peaked T waves, best seen in the chest leads. [1]
Check P waves and PR
As potassium rises, the PR interval gets longer and P waves flatten or disappear. [1]
Check the QRS
A widening QRS, a sine wave pattern or a slow rhythm are late, dangerous signs that can lead to cardiac arrest. [1]
Stabilize the heart
With ECG changes, give IV calcium (gluconate or chloride) right away to protect the heart while you lower potassium. [2]
Shift potassium into cells
Give IV insulin with dextrose and nebulized albuterol per protocol. Check glucose often after insulin. [1]
Remove potassium and find the cause
Stop potassium sources and drugs that raise it, and use binders, diuretics or dialysis as needed. Monitor the heart and recheck levels. [1]
Common errors
- Assuming a normal ECG means the potassium is safe.
- Waiting for a repeat lab before giving calcium when the ECG shows changes.
- Forgetting glucose checks after giving insulin.
Usual progression (levels are rough; changes can appear at any level) [1]
| Potassium (mEq/L) | ECG finding | Urgency |
|---|---|---|
| About 5.5 to 6.5 | Peaked T waves | Treat and monitor |
| About 6.5 to 7.5 | Long PR, flat or absent P waves | Emergency |
| Over about 7.0 | Wide QRS, slow rhythm | Emergency |
| Very high | Sine wave, VF or asystole | Cardiac arrest risk |
Practice it in VMS
In VMS you do this on the patient, not on paper: every step goes on the checklist with a score, and in Teach mode Blocky tells you what comes next.
VMS cases that train this skill
Sources
Facts and steps follow AAMC Core Entrustable Professional Activities (Core EPAs); NCCPA PANCE Content Blueprint. VMS is not affiliated with these organizations. Updated: 2026-10-11.