My bathtub hot water is running out slow, but the cold water runs good, have a single handle levler moen?

Sounds like you might have some crud blocking the hot water inlets on the cartridge.
Shut the water off ands open up the faucet. Remove the cartridge and check and clean the inlet ports. While the valve's open place a pan over it and turn the hot water on to flush out the supply. You should have a full sream when you do this. If not let me know. Good luck, Tom