Hit Points
Hit Points (HP) are the basic unit of character health in Urban Dead. When a character reaches zero hit points the character becomes a dead body, that must stand up as a zombie to continue gameplay.
The maximum number of Hit Points is fifty, though the Body Building skill increases the maximum to sixty (and remains in effect if the character becomes a zombie). Players with the Diagnosis (human) or Scent Blood (zombie) can see the HP values of survivors next to their names. Diagnosis carries over to your zombie character.
Losing Hit Points
Characters typically lose Hit Points by being attacked by other characters (alive or undead). When a character successfully attacks a target, the target loses Hit Points equal to the damage the attack deals.
Survivors also lose Hit Points from being infected by a bite attack from a zombie with Infectious Bite.
Anyone wearing a flak jacket takes 20% less damage from gunshot wounds. Flak jackets will have the same effect on your zombie character.
there is also a chance to lose hit points when atemting to free run into a ruined building.
Gaining Hit Points
The most effective method by which survivors can heal themselves or other survivors (or zombies, if they so wish, but that would be helping the zombie cause, not the survivors) is with first-aid kits, found mainly in mall drugstores and hospitals, though sometimes in churches. A first-aid kit grants 5HP to the person it is used on. The First Aid Skill allows survivors to heal 10HP from using a first-aid kit. First-aid kits are at their most effective when they are used by someone with the surgery skill in a powered hospital or infirmary. This makes them heal 15HP. Healing yourself gives you no XP. Healing another gives 5XP, regardless of the amount of HP healed.
Another method of gaining HP for survivors is through beer or wine, that are found in pubs (The "Something" Arms), clubs, and mall liquor stores, (wine is also found in churches) though these are inefficient, as they only heal 1HP per AP. Their only real use (apart from RP purposes) is to broadcast the fact you have body building to those with Diagnosis when you haven't got a first-aid kit yourself.
Zombies can heal themselves directly in only one way, and that is through using bite attacks with the skill Digestion. With this skill, each successful bite yields 4HP.
Another way to gain HP is to simply stand up. Standing up refreshes your HP. Unfortunately, you can only stand up if you're dead or revivifying. Standing up after death gives you your max HP, and after revivification gives you half the max HP.