Basic recovery
Keep food above 16 and hydration above 5 for Mortal's half-point regeneration roughly every four active seconds. Stasis regenerates one point on that interval. Completing the short nighttime bed-sleep transition adds four health, up to the 20-point cap.
Bandages
Two wool arranged vertically make three bandages. Select one and right-click to use it. A bandage restores six health and consumes one item in a finite mode. It does not directly refill food or water.
Herbal remedy
One glowcap mushroom and two wild berries form a herbal remedy in the grid. Select it and right-click. It clears poison and restores two health. The recipe is glowcap/berry across the top with one more berry beneath the first berry; the horizontal mirror is also accepted.
Milk
Milk a cow or goat with an empty bucket, then hold right mouse or R to drink the milk. Any animal-milk bucket clears poison and restores three food and up to eight hydration. You retain the empty bucket. Only portable water, rather than milk, is restricted to wooden drinking vessels.
Poison reduces health while active but does not itself take the final health point. Clear it before another hazard turns a manageable problem into a death.
Settlement doctors
A friendly settlement doctor can treat you when your trade protection/bond is active and you are injured or poisoned. The settlement must have actual bandage supplies. Treatment uses one stored bandage to restore eight health; clearing poison also requires a stored herbal remedy. If the doctor has no bandages, the interaction explains that wool supplies are needed.
This is a finite stock-based service, not unlimited free regeneration. Establish friendly trading relations and respect settlement property before relying on it.
Avoid losing your recovery supplies
Keep spare food, water and bandages in a home chest. Mortal death drops your carried inventory, armor and offhand. A safe wool-bed respawn and a small stocked recovery kit make it easier to retrieve the lost items.