Creatine: strong evidence for muscle, and a kidney number it moves on purpose

Creatine works, and it is cheap: 3 to 5 grams of creatine monohydrate a day is one of the best-evidenced ways to add strength, power, and a little muscle if you train. The catch worth knowing before your next physical is that creatine deliberately raises your serum creatinine, the blood marker labs use to estimate kidney function, so your kidney numbers can read worse while healthy kidneys keep filtering exactly as before.

What does creatine do?

Creatine is stored in muscle as phosphocreatine, a fast-recharge energy molecule your muscles tap for short, hard efforts like a heavy set or a sprint. Keeping those stores topped up lets you squeeze out a few more reps and recover faster between sets, which over weeks of training adds up to more strength, more power, and a little more lean mass ¹. The effect is real but modest: a few extra percent on your lifts, built over weeks.

The International Society of Sports Nutrition, a professional body of sports-nutrition researchers, put it plainly, calling creatine the most effective ergogenic (performance-boosting) supplement available to athletes ¹:

Creatine monohydrate is the most effective ergogenic nutritional supplement currently available to athletes with the intent of increasing high-intensity exercise capacity and lean body mass during training.International Society of Sports Nutrition position stand (Kreider et al., 2017) [[1]]

Beyond the gym, creatine has drawn interest for the brain, which also runs on phosphocreatine. The measured effects are modest and clearest when the brain is under stress, such as during sleep deprivation or in older adults, rather than a memory boost for well-rested young people ³. Treat any cognitive benefit as a possible bonus, not the reason to take it.

Is creatine safe for your kidneys, and why does it raise creatinine?

Short answer: in healthy people, creatine has not been shown to harm the kidneys, even at intakes far above the everyday dose and over years of use ²⁵. What it does do is raise your serum creatinine, and it does that by design, not by damaging anything.

That is why a flagged creatinine or a lower eGFR in someone who lifts and supplements is usually a reading problem, not a kidney problem, though it is the clinician who ordered the test, not you, who should make that call. The clean way to check is cystatin C, a different kidney-filtering marker that creatine does not affect; an eGFR based on cystatin C holds steady even as the creatinine-based one dips ². The practical move is simple: tell whoever reads your kidney labs that you take creatine, and if the number worries them, ask for the cystatin C based estimate. One caveat that matters: if the cystatin C based eGFR is also low, or your clinician is still concerned, treat that as a real finding to evaluate, not something to pin on creatine. For the markers themselves, see serum creatinine and eGFR.

If you started creatine and now have an eGFR in hand, the question is where it sits and how far it moved. Drop your number in below to see it against the standard kidney-function bands.

How much creatine per day, and do you need to load?

The everyday dose is 3 to 5 grams of creatine monohydrate a day, taken continuously. That is enough to saturate your muscle stores and keep them there, and reaching full saturation takes about 3 to 4 weeks at that pace ¹.

Loading (a short stretch of about 20 grams a day) gets you to full stores in roughly a week, which matters if you have a competition or a training block starting soon; otherwise it mostly buys faster bloating and, for some people, loose stools. Creatine has been taken at up to 30 grams a day for as long as five years without harm in healthy people ¹, but a bigger dose does not build more muscle once your stores are full, so there is no reason to chase it.

When to take it, and which form to buy

Timing barely moves the needle. Daily consistency is what keeps your stores full, so take creatine whenever you will remember, with or without food.

On the label, plain creatine monohydrate is what you want, ideally one that is third-party tested (look for NSF Certified for Sport or Informed Sport), since supplements are not checked by the FDA for label accuracy before sale ⁴. Fancier forms cost more to solve problems monohydrate does not have.

Creatine is well worth its low price for strength and muscle, and the kidney scare attached to it is mostly a misread lab: keep the dose ordinary, buy plain monohydrate, and tell whoever reads your kidney panel that you take it.