Creatine and Acute Kidney Injury Risk
There is no established dose of creatine that definitively causes acute kidney injury in healthy individuals, and current evidence suggests that creatine supplementation at recommended doses (3-5 g/day maintenance, up to 20 g/day loading) does not impair kidney function in people with normal baseline renal function. 1, 2
Evidence from Clinical Studies
Safety in Healthy Populations
Short-term and long-term creatine supplementation (ranging from 5 days to 5 years) at doses between 5-30 g/day showed no significant effects on kidney function markers including glomerular filtration rate in healthy athletes and bodybuilders without underlying kidney disease. 2
Studies examining liver enzymes, urea, glomerular filtration, and albumin excretion rates demonstrated no changes in functionality even during several months of supplementation in both young and older healthy populations. 1
A case study of a 20-year-old man with a single kidney and mildly decreased GFR (81.6 mL/min/1.73 m²) showed no change in measured GFR after 35 days of high-dose creatine (20 g/day for 5 days, then 5 g/day for 30 days). 3
Isolated Case Reports of Kidney Injury
Despite the generally favorable safety profile, there are rare case reports suggesting potential nephrotoxicity:
An 18-year-old man developed acute tubular necrosis while taking creatine monohydrate at recommended doses, with full recovery 25 days after discontinuation. 4
A 24-year-old weight lifter developed acute interstitial nephritis while taking creatine along with multiple other supplements, recovering completely after stopping all supplements. 5
These isolated cases cannot establish causation, as confounding factors (polypharmacy with other supplements, underlying undiagnosed conditions, or idiosyncratic reactions) may have contributed to the kidney injury. 5
High-Risk Populations to Avoid Creatine
Creatine supplementation at doses exceeding 3-5 g/day should not be used by individuals with pre-existing renal disease or those with potential risk factors for renal dysfunction, including:
- Diabetes mellitus 1
- Hypertension 1
- Reduced glomerular filtration rate at baseline 1
- Pre-existing chronic kidney disease 2
Metabolic Considerations
High-dose creatine supplementation (20 g/day) can increase urinary excretion of methylamine and formaldehyde (potential cytotoxic metabolites), though these increases remain within normal ranges and have not been definitively linked to adverse kidney effects. 1, 2
Creatine supplementation increases serum creatinine levels through increased creatine-to-creatinine conversion, which can falsely suggest kidney impairment when using creatinine-based estimates of kidney function. 3
Clinical Monitoring Recommendations
For healthy individuals choosing to use creatine supplementation:
- Pre-supplementation kidney function assessment may be considered for safety but appears unnecessary in normal healthy subjects 1
- If monitoring is performed, use measured GFR rather than creatinine-based estimates, as creatinine levels will artificially increase 3
- Monitor for symptoms of kidney dysfunction (nausea, vomiting, decreased urine output) 4
Bottom Line
No specific dose threshold for creatine-induced AKI has been established in the medical literature. The supplement appears safe at standard doses (3-5 g/day maintenance, 20 g/day loading for 5-7 days) in healthy individuals, but should be avoided entirely in those with existing kidney disease or risk factors for renal dysfunction. 1, 2