Minecraft wiki entry for Horses, associated text: The health can be determined by looking at the heads-up display (HUD.) The saddle icons replacing your hunger bar while riding a horse is the horse’s health bar. One heart equals two health points. When you ride a horse that has an odd number of health points, the last health point isn’t shown on the HUD. Sometimes, horses have an odd number of health; one method you can check if the horse has an even or odd number of health points/hitpoints is by hitting the horse and mounting the horse to check the hitpoints. If the HUD shows one less health point lost in health than the attack damage of the player, after the player attacks it, either with or without tools, the horse has 1 more health point than shown in the HUD and thus has an odd number of health. If the HUD shows the exact amount lost in health than the total attack damage of the player after the player attacks it, the horse has an even number of health and it has exactly the number of health points/hitpoints as shown in the HUD. The horse might regenerate one health point right after you attack it, so you might want to try again. Heal the horse to full health and attack it again to check again if you’re correct in checking if the horse has an odd or even number of hitpoints. For example, if a horse appears to have 22 hitpoints and you attack it, if the horse has lost one fewer health points than the damage you inflicted to the horse and if the horse didn’t regenerate, then it means that the horse actually has 23 hitpoints.