There is a figure for this. If you are in bed, you should move or be moved about every 2 hours.
About every 2 hours is the whole of the instruction. There’s no separate figure for different people, and no set answer for what to do if two hours isn’t possible — which, for a family caring for someone at home, is often the real question.
Repositioning is part of a larger instruction, which is to relieve the pressure on the area. The other half is equipment. Use pillows, foam cushions, booties, or mattress pads to reduce the pressure. Some pads are water- or air-filled to help support and cushion the area. What type you use depends on the wound and on whether the person is in bed or in a wheelchair. Talk with your provider about what choices would be best, including what shapes and types of material.
Two hours is the number for a bed. There’s a different one for a chair: if you are in a wheelchair, try to change your position every 15 minutes.
How the move is made matters as well as how often. Avoid further injury or friction by not slipping or sliding as you move positions, and try to avoid positions that put pressure on your sore. And do not massage the skin near or on the ulcer. This can cause more damage.
Repositioning is also not the whole of prevention. Check your skin for pressure sores every day, and ask your caregiver or someone you trust to check areas you cannot see.