Creatine Will Raise Your Creatinine. Here's Why That's Not Kidney Damage.
The most persistent myth surrounding creatine supplementation is that it harms the kidneys. The concern stems from a real and measurable observation — creatine does raise serum creatinine — but the interpretation of that observation is wrong in a way that has put a lot of people off one of the most well-researched supplements available.
Understanding the Mechanism
Creatine is stored in skeletal muscle primarily as phosphocreatine. It degrades spontaneously and irreversibly into creatinine at roughly 2% per day. Creatinine is a metabolic waste product, filtered by the kidneys and excreted in urine.
Standard kidney function tests measure serum creatinine and use it to estimate glomerular filtration rate (eGFR). The equation built into that calculation assumes relatively constant creatinine production. When you supplement creatine and increase total body stores, your muscles produce more creatinine. The equation interprets the elevated reading as reduced kidney filtration.
It is not. It is more substrate producing more waste at the same filtration rate. The kidneys haven't changed — the input to the equation has.
What the Research Actually Shows
A 2025 systematic review and meta-analysis examining 21 studies on creatine supplementation and kidney function found exactly this pattern. Creatine was associated with a small but statistically significant rise in serum creatinine (mean difference: 0.07 micromol/L). However, there were no changes in measured GFR, cystatin C, proteinuria, or albuminuria — the markers that genuinely reflect kidney health, independent of creatinine metabolism.
The creatinine number moved. Every actual indicator of kidney function did not.
Kreider and colleagues (JISSN, 2025) conducted the largest creatine safety analysis to date, reviewing 685 human clinical trials involving over 26,000 participants. Side effect prevalence was nearly identical between creatine and placebo: 4.60% vs 4.21% (p=0.828). No significant differences were observed across any of the 49 side effects evaluated, including all renal function markers. Some of these trials ran for up to 14 years.
The Case Reports People Cite
Case reports linking creatine to kidney injury almost invariably involve individuals with pre-existing renal conditions, concurrent use of substances known to affect kidney function, or extreme exertion-related rhabdomyolysis. These are confounded cases. They do not establish a causal relationship between creatine supplementation and kidney damage in otherwise healthy people.
What to Do About Your Bloodwork
If you supplement creatine and have routine blood panels done, there's a reasonable chance your GP will flag your creatinine and eGFR values. This is not a sign that your kidneys are failing. It's a sign that the standard calculation wasn't designed with creatine supplementation in mind.
The practical fix is straightforward: tell your doctor you take creatine and ask for a cystatin C-based eGFR. Cystatin C is produced at a constant rate by all nucleated cells and is entirely unaffected by creatine intake. It gives you an accurate kidney function reading without the interference.
A Note on Pre-Existing Kidney Disease
Most creatine studies have been conducted in healthy populations. For individuals with diagnosed renal impairment, the data is more limited. Pilot studies in haemodialysis patients haven't shown adverse effects beyond the expected creatinine rise, but caution is warranted until a stronger evidence base exists for that population specifically.
The Bottom Line
Creatine raises serum creatinine because of basic biochemistry — more creatine stored in muscle means more creatinine produced. That's arithmetic, not pathology. When you measure kidney function with markers that aren't influenced by creatinine metabolism, creatine supplementation shows no adverse renal effect in healthy individuals, even across years of use.
If your blood results look unusual after starting creatine, the number to question is the creatinine-based eGFR — not the supplement.
References
- Kreider et al., JISSN, 2025
- 2025 Systematic Review/Meta-Analysis: Effect of creatine supplementation on kidney function