Long-term oral creatine supplementation does not impair renal function in healthy athletes
Poortmans & Francaux (1999) · Medicine & Science in Sports & Exercise
Topics: Safety & Kidney
- Study type: Cohort study
- Population: Healthy athletes
- Dose: 1-20 g/day
- Duration: Up to 5 years
- Published: 1999
What the study found
A cornerstone safety study. Athletes who had used creatine for up to five years showed no impairment in kidney (renal) function compared with non-users, directly addressing the most common creatine safety concern.
Key findings
- No difference in glomerular filtration rate or kidney markers between long-term users and controls.
- Slightly higher creatinine is a harmless byproduct of creatine metabolism, not kidney damage.
- Supports long-term safety in people with healthy kidneys.
The practical takeaway
The 'creatine harms your kidneys' myth doesn't hold up in healthy people — but those with kidney disease should consult a doctor.