Shield wielder +10% Health
Celtic moustache +12% Health BONUS: +15% Health (while heavy machine guns equipped)
Medic Jacket +12% Health (Will talk about passive below)
U.F Pants +12% Health
Skill tree +15% Health
This equals 76%, but Medic Jacket also gives 30% damage reduction when you have Medikit equipped. To calculate how much health this would be equivalent to, we have to do the following. Think about it this way, if it was 50% DMG reduction, it would be the same as you having double your health.
In the case of 30% DMG reduction, we have to do 100/((100-30)/100) which equals 142, meaning 42% extra health. If we add these up, it's 76% + 42% = 118% TOTAL HEALTH!