🧪 Fractional Excretion of Potassium (FEK)
UseWhen to use: hypokalemia workup when deciding renal vs extrarenal potassium loss.
StrataIn hypokalemia, high FEK favors renal wasting; low FEK favors GI/skin losses or low intake.
LimitsWhen not to use: unstable creatinine / unmatched samples. · Pitfall: diuretics confound FEK. · Not a stand-alone diagnosis.
SourceStandard FEK teaching formula
This-shift next steps
After scoring: open the scene pack, peer scores, and the matching pathway. Local reference — no HIS write.
Paste the link in Slack, Teams, X, or LinkedIn — the preview image comes from this page’s Open Graph card.
Methodology · worked example, guidelines & full notes
(UK×PCr)/(PK×UCr)×100%.
When to use
When to use: hypokalemia workup when deciding renal vs extrarenal potassium loss.
How it works
FEK = (UK × PCr) / (PK × UCr) × 100%.
Key points
- (UK×PCr)/(PK×UCr)×100%.
- Hypokalemia phenotyping adjunct.
- Next: Mg, ABG, meds review.
References
- Standard FEK teaching formula
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Urine K | 40 mEq/L |
|---|---|
| Plasma K | 3.0 mEq/L |
| Urine creatinine | 80 mg/dL |
| Plasma creatinine | 1.0 mg/dL |
→FEK16.7%
- UK/PK：13.33
- Cue：≈10–20% — intermediate FEK teaching band
Verification & sources · governance
FAQ
Frequently asked questions
- Does Fractional Excretion of Potassium (FEK) upload patient data? Where is it calculated?
- Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
- How is Fractional Excretion of Potassium (FEK) calculated in practice? Can you show a worked example?
- Inputs: Urine K 40 mEq/L, Plasma K 3.0 mEq/L, Urine creatinine 80 mg/dL, Plasma creatinine 1.0 mg/dL → Result: FEK 16.7 %（UK/PK: 13.33, Cue: ≈10–20% — intermediate FEK teaching band）