What happens inside your body when you take creatine?

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 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 supplements might tell your body to make less of its own creatine by turning down a key enzyme, kind of like turning off a faucet when you're already getting water from another source.

Your body makes its own creatine, and the only place you can get it from food is meat — plants don’t have any form of creatine your body can actually use.