Low to no hot water pressure from bath tub faucet and shower head

You do not give much info so pipe could be frozen or clogged. I would remove the shower head and turn the hot water on and see if I get pressure or if some rust blows out. If you have pressure then clean or replace the showwer head if no pressure it has to be the control valve or clogged pipes. A good guess is the water control knob for the hot water has a problem and should be rebuilt or replaced