As you play Rules of Survival you're bound to get hurt. If it's a scratch or a bullet to the face, the many medical items below scattered around the map can help you get back into the fight.
Bandages (10 HP)
Sports Drink (Heals overtime)
Med Kit (Heals 45)
First-Aid Kit (Heals 100)
Cardio and Tonic (Heals overtime)