I have hot water but the pressure is very low the cold water is fine and all the other taps in the house are fine for hot water pressure

Sounds like you have debris inside your faucet hot port, Please tell us if this is shower, kitchen or sink faucet and tell us the model number, Thanks.

John

Two knob or single lever?

If you have Posi-Temp built in, it could just be either a deffective faucet or a safety stopper inside the faucet handle is incorectly positioned. If it is a single lever for the shower just find the screw holding the handle (moen hides these pretty well).