Sorry I mistyped. I can’t believe I typed that I meant to say carnitine.
Creatine is a cofactor for producing energy. I don’t supplement with creatine. Although potentially I could be short of creatine for the same reason I may be short of carnitine.
Carnitine is what I supplement. Specifically L-carnitine is the one that animals use (the other kind d-carnitine is toxic to us). It is used to shuttle long chained fatty acids into mitochondria to be burned.
We make Carnitine from amino acids (we also make creatine that way too) and one of the steps that we use (methylating the amino acid lysine) is one for which I may be genetically constrained by my methylation status (MTHFR mutation).
In theory for someone like me who methylates less efficiently carnitine could become a rate limit for how fast I can burn fat for energy. I have noticed less energy constraints when cycling so maybe Tommy Wood has a point. It’s not something that would build up if I get too much - I’d just be making expensive pee so I’m happy to supplement just in case.