When you start the run, your Max Health is your Loadout Health.
Some perks / benefits work relative to your Max Health (which can increase during the run from perks or from Miasma’s Absorb), while others work relative to the Loadout Health (which generally doesn’t increase in a run but can be boosted by Health from Mystery Crates)
Bonus Healing
Any healing effects (including Miasma’s Absorb and Mortis’ Plague Cloud) are improved by the following:
- +10% Healing for all heroes from Dr. Toxic (at Level 20 and again at 50) and Prospero (Level 20)
- +30% Healing for Arctor at Level 10
- +20% for each Combat Medic perk
- +2% Healing Bonus in the Skill Tree for some heroes
Tank (Increase Max Health only)
Tank increases your Max Health by x1.5. So if it’s the only Health perk it increases Max Health by 50% of your Loadout Health. But if you have 1 Max Health Up (so health is 1.2 x LoadOut Health) Tank stacks with it to give you 1.8 x Loadout Health (=1.2 x 1.5)
There is no healing apart from the healing you anyway get for Levelling up (if you get it from a perk roll, rather than from a Hidden Treasure)
Max Health Up (Increase Max Health and Heal)
MaxHealthUp increases your Max Health by, and heals by, 20% of your Loadout Health. If you get it from a perk roll (rather than from the Angel or Hidden Treasure) you also get the healing from Levelling up
Gun Heart (Increase Max Health and Heal)
GunHeart increases your Max Health by, and heals by, 10% of your Loadout Health. It also boosts your attack by 15% of your Weapon-specific Base Damage
Heal (Heal only)
Heal (from the Angel or from the Hidden Treasure) heals you by 40% of your Max. Health
Combat Medic (Heal only)
Apart from adding 20% bonus to your Healing, Combat Medic also heals when you take it (regardless of how you get it). The healing is 10% of Max Health and the 20% bonus will already apply.
If you get it from a perk roll (rather than from the Angel or Hidden Treasure) you also get the healing from Levelling up, and the 20% bonus will apply here too
Life Steal / Great Life Steal (Heal only)
Life Steal heals 2% of Loadout Health per kill, while Great Life Steal (appeared in a Battle Pass, then in some endless events but wasn’t included in the 2021 Summer Endless event) heals 5%
Band Aid (Heal only)
Band Aid heals 7% of your Max Health each time you clear a room
Health Kit (Heal only)
These are the little hearts that you get from killing bosses, and from the harmless green enemies in the room before the boss room (except in Castles) and randomly from kills (the chances of this can be increased by the Health Item Drop Bonus skill)
Health Kit healing = 100 + First Aid permanent upgrade + 5% of Max Health
Levelling up (Heal only)
Each time you level up, you heal by your Regen Mastery permanent upgrade