Creatine and your blood values: what actually changes?

Creatine raises your creatinine slightly and changes how much water you hold, but it does not damage the kidneys in healthy people. That small rise makes sense: creatinine is the breakdown product of creatine. It is an arithmetic consequence of your supplement, not an alarm signal.

Creatine is one of the best studied supplements out there. Yet that one blood value still causes needless worry.

Does creatine raise your creatinine?

Yes, creatine can raise your creatinine slightly, and that is normal. Your body breaks creatine down into creatinine, so more creatine in your muscles means a bit more creatinine in your blood. That rise usually sits within or just above the reference range and does not mean kidney damage.

Because creatinine is used to estimate your kidney function, your eGFR can look slightly lower as a result. Your kidneys simply keep working.

Is creatine safe for your kidneys?

In healthy people, creatine at normal doses is described as safe. Meta-analyses and sports-nutrition position stands find no harmful effect on kidney function at doses up to 5 grams a day (Kreider, 2017; Antonio, 2021). If you have an existing kidney condition, discuss it with your doctor first.

The worry around creatine and kidneys comes largely from the confusion with the creatinine value, not from demonstrated damage.

What else changes in your blood and body?

Creatine draws water into your muscle cells, which shifts your hydration and your weight early on. That explains the few kilos many people gain in the first weeks. It is fluid in the muscle, not fat.

How do you test your blood values on creatine?

For a clean picture of your kidneys, do not judge them on creatinine alone. Cystatin C does not depend on your muscle mass or your creatine use, so it often gives a fairer picture (Baxmann, 2008). Combine it with creatinine and urea.

Test on a calm day and drink enough. Our kidney health blood test bundles those markers, so you can track your baseline and your trend.

Read on: blood values for strength athletes, high creatinine from muscle mass and protein intake and your kidneys.

My advice: do not let a slightly raised creatinine keep you off creatine if your kidneys are healthy. If you want certainty, add cystatin C and discuss a persistent deviation with your GP.

References

1. Kreider RB, Kalman DS, Antonio J, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. Journal of the International Society of Sports Nutrition. 2017. PMID: 28615996.
2. Antonio J, Candow DG, Forbes SC, et al. Common questions and misconceptions about creatine supplementation: what does the scientific evidence really show? Journal of the International Society of Sports Nutrition. 2021. PMID: 33557850.
3. Baxmann AC, Ahmed MS, Marques NC, et al. Influence of muscle mass and physical activity on serum and urinary creatinine and serum cystatin C. Clinical Journal of the American Society of Nephrology. 2008. PMID: 18235143.

Disclaimer

Every blood test result includes a professional assessment by a BIG-registered doctor. This article gives general information and is not a substitute for medical advice. A blood test is a tool to walk into the conversation with your GP better informed, not a diagnosis in itself. For treatment decisions, discuss your results with your GP.