If healthy young adults take a high dose of creatine for a week, their body shows big changes in certain chemicals in the blood — some go up, one goes down — but nothing changes much after that during a long lower-dose phase.

Taking creatine every day for 20 weeks lowers a substance in your blood called guanidinoacetate—by half in the first week and by about a third afterward—which suggests your body starts making less of its own creatine.

If young, healthy guys take a lot of creatine for 5 days straight, their muscles soak it up and end up with about 21% more creatine inside them.

Taking creatine powder for about a week—first a lot, then a little—can boost the amount of creatine in your muscles by over 13%, which helps your muscles store more energy.

If young, healthy guys take a lot of creatine with a high-carb diet after a tough workout, their muscles store more creatine within just a few days — and it keeps going up the longer they take it.

Taking 21 grams of creatine a day for 5 days can boost the amount of creatine in your muscles by about 30%, but it doesn’t make your muscles build protein faster or break it down slower, whether you’ve eaten or not.