Creatine and Your Kidneys: What the Research Says

For people with healthy kidneys, creatine at normal doses doesn't damage them. That's the consistent finding from controlled trials lasting up to five years, including studies that measured kidney function directly rather than relying on a blood test (Kreider et al., 2017).

The worry is understandable, because creatine does change one of the main numbers doctors use to check your kidneys. It raises your blood creatinine slightly, and that can make healthy kidneys look like they're struggling on paper. If you already have kidney disease, the picture is different, and you should talk to your doctor before taking it.

The short answer

Why creatine affects your blood test

When your muscles use creatine, a small amount breaks down each day into a waste product called creatinine. Your kidneys filter creatinine out of your blood, so doctors measure it to estimate how well they're working. The lab turns your creatinine into an eGFR, an estimated filtration rate. Higher creatinine means a lower eGFR, which looks like worse kidney function.

Take creatine and there's more of it to break down, so your creatinine rises a little even though your kidneys are filtering exactly as well as before. Muscle mass does the same thing: a muscular person often has higher creatinine than a smaller person with identical kidneys. It's a known limitation of the test, not a sign of damage.

A 2025 meta-analysis of 21 studies found exactly this pattern: creatine caused a small, statistically significant rise in creatinine, but no difference in kidney filtration rate (GFR) between the creatine and placebo groups (Naeini et al., 2025). The authors put the creatinine rise down to creatine's normal breakdown, not to kidney impairment.

Cystatin C: the test that creatine doesn't affect

Cystatin C is another blood marker of kidney function. It isn't made from creatine, so supplements don't push it up. In a 3-month trial, men taking about 10 g of creatine a day saw their cystatin C move the same way as the placebo group's, with no sign of harm (Baxmann et al., 2008). If a routine test flags your kidneys while you're taking creatine, asking about a cystatin C test is a sensible next step.

What the studies show

The type 2 diabetes trial is worth a closer look, because diabetes is a leading cause of kidney disease. Researchers measured kidney filtration with a radioactive tracer, which is far more precise than a creatinine estimate. After 12 weeks it was essentially unchanged: 90 to 96 mL/min in the creatine group, against 98 to 96 in the placebo group (Gualano et al., 2011).

The International Society of Sports Nutrition reviewed the full body of research and concluded there's no compelling evidence that creatine harms the kidneys in healthy people at recommended doses (Kreider et al., 2017).

If you have kidney disease

This is where caution matters. The trials above were mostly in people with healthy kidneys, and the research in people with existing kidney disease is much thinner. There's a published case report from 1998 of a young man with pre-existing kidney disease whose kidney function worsened while he was taking creatine and recovered after he stopped.

One case report doesn't prove creatine caused the problem, but it's enough reason to be careful. If you have chronic kidney disease, a single kidney, a kidney transplant, or have been told your kidney function is reduced, don't take creatine unless your kidney doctor agrees.

Other conditions that put kidneys under strain are worth mentioning to your doctor too: diabetes, high blood pressure, and regular use of anti-inflammatory painkillers (NSAIDs such as ibuprofen).

How to take creatine with your kidneys in mind

1. Stick to 3 to 5 g a day. That's the dose with the most safety data. There's no benefit to taking more. Our creatine calculator works out yours.
2. Tell your doctor you take it, especially before a blood test, so a raised creatinine isn't misread.
3. Ask about cystatin C if a routine test comes back borderline.
4. Buy plain, tested monohydrate. Multi-ingredient products and pre-workouts add unknowns. Look for NSF Certified for Sport or Informed Sport. See the best form of creatine.
5. Drink normally. You don't need extra water for your kidneys' sake.

Our broader page on whether creatine is safe covers the liver, hair, cramps and long-term use.

Questions people ask

Is creatine bad for your kidneys?

Not if your kidneys are healthy. Trials of up to five years at normal doses found no kidney damage. People with kidney disease should only take it with their doctor's approval.

Does creatine raise creatinine?

Yes, slightly, because creatine breaks down into creatinine. That can lower your eGFR on paper without any real change in kidney function.

Should I stop creatine before a blood test?

Tell your doctor you take it instead. If they want an unaffected reading, a cystatin C test isn't influenced by creatine, or they may ask you to pause it for a few weeks first.

TD

Written by Tom D

Tom has trained in the gym for years and has taken 5 g of creatine every day for about a decade, with magnesium on and off for most of the year. Reading the research behind supplements started as a hobby; this site is where he writes it up. He isn't a doctor or dietitian, so every claim links to the study behind it.

Sources

1. Kreider et al. 2017, ISSN position stand on creatine safety and efficacy (JISSN)
2. Poortmans & Francaux 1999, Long-term creatine and renal function in athletes
3. Baxmann et al. 2008, Creatine and renal function: randomized controlled trial
4. Gualano et al. 2011, Creatine and kidney function in type 2 diabetes
5. de Souza e Silva et al. 2019, Creatine and renal function: systematic review
6. Naeini et al. 2025, Creatine and kidney function: systematic review and meta-analysis

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