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 creatine in two steps: first, it combines glycine and arginine to make a middle substance, then it adds a methyl group to turn that into creatine.

A chemical that looks like creatine can block muscle cells from taking in creatine — in rat muscle tests, it stopped 82% of the creatine from getting in when used at a certain strength, which means it might be pretending to be creatine to get in first.

The best way to get the building blocks your body needs to make creatine is by eating meat and fat from animals like cows and sheep.

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.