What Is Creatine? How It Works and What It Does

Creatine is a natural compound your body uses to make energy quickly. It's built from amino acids, stored mostly in your muscles, and used in the first few seconds of any hard effort: a heavy lift, a sprint, jumping off the floor. Taking it as a supplement tops up those stores so your muscles can do a little more work before they tire.

It isn't a steroid, a hormone or a stimulant. Your body makes some every day, you get more from meat and fish, and supplements simply add to what's already there. It's also one of the most researched supplements in existence, with hundreds of controlled trials behind it.

A note from me, Tom: I've taken 5 g of creatine monohydrate a day for about ten years. This page is the explanation I wish I'd had when I started.

Where creatine comes from

Your body needs to replace roughly 1 to 3 g of creatine a day, depending on how much muscle you carry (Kreider et al., 2017). About half of that comes from food. The rest your body makes itself, mainly in the liver and kidneys, from the amino acids arginine and glycine.

The food sources are red meat and seafood. A pound of uncooked beef or salmon provides about 1 to 2 g. A normal mixed diet supplying 1 to 2 g a day leaves your muscles roughly 60 to 80% full. That gap is what supplements fill.

Plant foods contain almost no creatine, so vegetarians and vegans start with lower stores. They tend to see a bigger jump when they start supplementing.

Where it's stored

About 95% of the creatine in your body sits in your skeletal muscles. The other 5% is mostly in the brain and testes.

Inside the muscle, about two-thirds is stored as phosphocreatine, a form with a phosphate group attached, and the rest as free creatine. That split matters, because phosphocreatine is the part that does the work.

How creatine works

Your muscles run on a molecule called ATP. When a muscle contracts, it breaks ATP down and releases energy. The catch is that muscles only hold a few seconds' worth of ATP at any moment.

That's where phosphocreatine comes in. It hands its phosphate group back to the spent ATP, rebuilding it almost instantly. This is the fastest energy system your body has. It powers roughly the first 10 seconds of all-out effort, before slower systems that burn carbohydrate and fat take over.

Supplementing raises the creatine and phosphocreatine in your muscles by about 20 to 40% above what a normal diet gives you. With fuller stores, your muscles can rebuild ATP a bit longer and recover between efforts a bit faster. In practice, that means an extra rep or two per set, or slightly faster repeat sprints.

What creatine actually does for you

The effect on any single workout is small. The value comes from adding up those extra reps over weeks and months of training.

The most important line in that table is the last one. Creatine helps you train harder. If you don't train, there's little for it to amplify.

For women specifically, including after menopause, see our guide to creatine for women.

What creatine isn't

• It isn't a steroid. Creatine doesn't act like a hormone and isn't on any anti-doping banned list. A review of twelve studies found ten showed no change in testosterone, and the other two found only small changes within the normal range.
• It isn't a stimulant. It won't make you feel energized the way caffeine does. Most people feel nothing at all from a single dose.
• It isn't fat-burning. It contains no calories and doesn't change how your body stores fat. A small rise on the scale in the first weeks is water inside muscle, not fat. Our page on creatine bloating and water weight explains why.
• It isn't new. Scientists identified it in meat in 1832, and athletes have used supplements since the early 1990s.

How to take it

The short version: 3 to 5 g of creatine monohydrate a day, every day, at whatever time you'll remember. A loading phase is optional. Our creatine dosage guide covers the details, including loading, timing and what to mix it with.

Monohydrate is the form to buy. It's the one used in almost all the research, it's the cheapest, and newer forms haven't beaten it in head-to-head trials. Our comparison of creatine forms goes through HCl, micronized, Creapure and the rest.

Is it safe?

For healthy adults at normal doses, yes. Studies have run for up to five years, and the International Society of Sports Nutrition found no compelling evidence of harm to kidney function in healthy people. The only side effect that shows up consistently is a small amount of weight gain from water held in muscle.

There are exceptions worth knowing about, including existing kidney disease and pregnancy. Our page on whether creatine is safe covers who should check with a doctor first.

Questions people ask

Is creatine natural?

Yes. Your body makes creatine from amino acids, and you get more from meat and fish. Supplements are made synthetically, but the creatine is identical to the kind in your muscles, and it contains no animal products.

Is creatine a steroid?

No. It doesn't act like a hormone, and it isn't banned by anti-doping agencies. Studies of testosterone mostly found no change at all.

Will I feel creatine working?

Probably not from a single dose. It isn't a stimulant. Most people notice it as an extra rep or two in their sets after three or four weeks of daily use.

Do I need creatine if I eat meat?

You don't need it, but a typical diet leaves your muscles only 60 to 80% full. A supplement takes them close to their limit, which is where the performance benefit comes from.

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. Antonio et al. 2021, Common questions and misconceptions about creatine (JISSN)
3. Smith-Ryan et al. 2021, Creatine supplementation in women's health (Nutrients)

We link to the original study wherever we can. Read how we grade evidence and choose products.