Why your eGFR drops on creatine
eGFR is calculated from serum creatinine, which is assumed to come only from muscle turnover. Supplementing creatine adds an external source, so creatinine rises by roughly 10–30 µmol/L and eGFR falls proportionally. Nothing has happened to the filters. If a clinician does not know you take creatine, this can be misread as new kidney disease and trigger unnecessary investigation.
Getting an accurate answer
- Tell your GP you take creatine, and for how long.
- Repeat the test after 2–3 weeks off the supplement.
- Ask about a cystatin C-based eGFR, which is not affected by creatine or muscle mass.
- Check the urine ACR — a normal ACR alongside a modestly reduced eGFR in a muscular person is reassuring.
If you already have CKD
The trials showing safety were done in people with normal kidney function. In CKD the concerns are the extra nitrogen load, the difficulty of monitoring, and product purity in unregulated supplements. Discuss it with your nephrologist rather than deciding alone — and remember that resistance training itself, without supplements, is beneficial in kidney disease.









