You don't have much health as you roam about the time loop trying to put it right, so keeping on top of all the ways to heal yourself is paramount to your success. Deathloop is a game of gaming things slow, researching, and making a master plan, but one mistake, and it could be all over.
Deathloop uses the Dishonored health mechanic. If you take damage, your health becomes highlighted, and you can regain what is lost upon finding cover and waiting it out—your health will begin to recover, but not entirely. But if you take damage when your health is highlighted, you will lose everything highlighted, and then some.
You have ways beyond waiting it out and recovering naturally. You can find Fiz-Pop bottles throughout the houses and world that will heal you instantly upon use. Plus, there are health stations that exist that will heal you back to full, but these are limited and not practical to find in dire straights.
The last thing that can heal you is certain trinkets, but these will not instantly heal you, like Fiz-Pop. These are more like buffs to help your healing needs, such as regenerating life faster or healing a bit more using Fiz-Pops.
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