A potassium of 5.1
| Where it fallscommonly reported adult reference ranges | Hyperkalaemia |
|---|---|
| Potassium | 5.1mmol/L |
| Usual reference range | 3.5 – 5.0mmol/L |
| Severe hypokalaemia | under 2.5mmol/L |
| Moderate hypokalaemia | 2.5 – 2.9mmol/L |
| Mild hypokalaemia | 3 – 3.4mmol/L |
| Normal | 3.5 – 5mmol/L |
| Hyperkalaemiathis reading | 5 – 5.9mmol/L |
| Severe hyperkalaemia | 6 and abovemmol/L |
Notes
- One reading is not a diagnosis. Potassium moves with kidney function, diuretics, ACE inhibitors and ARBs, insulin, vomiting or diarrhoea — and how the blood sample itself was taken. A clinician reads it against your history and usually against a repeat, not on its own.
- Reference ranges differ between laboratories. The bands above follow commonly reported adult reference ranges. Your own report prints the range its analyser was calibrated against, and that printed range is the one to compare against — a difference of a few units between labs is normal and does not mean either is wrong.
- A high potassium is a false alarm often enough that laboratories name the artefact. Pseudohyperkalaemia happens when red cells break during collection — a tight tourniquet, a fist clenched repeatedly, a fine needle, a shaken tube, or a sample left too long before processing — releasing potassium into the serum. A raised result in someone with normal kidneys, on no relevant medicine and with no symptoms is repeated before it is treated.
- Potassium is one of the few results where the number itself is the emergency. Above about 6.5 mmol/L the risk is cardiac arrhythmia, and an ECG is done immediately rather than waiting for a repeat. It is also why medicines that raise potassium — ACE inhibitors, ARBs, spironolactone, trimethoprim — are monitored with blood tests rather than by symptoms, because there usually are none until the heart is affected.
What potassium of 5.1 mmol/L means
A reading of 5.1 mmol/L falls in Hyperkalaemia by commonly reported adult reference ranges.
The usual reference range is 3.5 – 5.0 mmol/L.
Reading it next to the rest of the picture
A single figure is a snapshot. What somebody experienced does with it is set by what sits around it — the other figures on the same report, the history behind them, and what the previous result was. Two people can hand over the same number and leave with different advice, and neither has been given the wrong answer.
That is also why the bands on this page are drawn from a named source rather than a rounded rule of thumb. A threshold is a decision point somebody argued for in print, not a law of nature, and knowing which document a line comes from is what lets you tell a meaningful result from a borderline one.
Nearby sizes
Read more
- CBC Normal Ranges — What Each Line on the Result MeansA value marked high or low on a CBC is common and is often not significant on its own. The pattern across lines is what a clinician reads.
- eGFR Normal Range: Above 90, and the Stages Below IteGFR is an estimate built from creatinine, age and sex — and the estimate is better than the raw creatinine it comes from, for a reason worth understanding.
- TSH Normal Range: 0.4–4.0 mIU/L, and the Number Moves BackwardsTSH runs opposite to the gland it measures. High TSH means the thyroid is underactive, and that inversion catches almost everyone reading their own result.
- Cholesterol Numbers: What Total, LDL, HDL and Triglycerides MeanA lipid panel reports four numbers and the one printed largest — total cholesterol — is the least useful of them.