First Aid Med

9 fixed on Standard (same on Village of Shadows):

• Old Man's House: breakable crate by the door (chapter 2).
• Tower of Worship Battlements: barrels at the top of the NW stairs, right before Mutated Dimitrescu (chapter 4).
• Drowned Houses (Reservoir): wooden cabinet on the north side (chapter 8).
• Stronghold: barrel on the north side of the Main Hall B1 level, candlelit ledge on the west side of the Small Cavern's south chamber and alcove in the west wall of the Large Cavern (chapter 10).
• Factory: metal desk NW in the Power Room and table NW in the Scrapheap (chapter 11).
• Altar: large weapons crate SW, after the Factory.

The Duke also sells it and the Survival Resources Pack includes 1.

Restores all of your health ("Medicine that fully heals all wounds"). Use it with the heal button (R on Control Type A) without opening the menu, or from the inventory with "Use". It does not work at full health, nor while you drive Heisenberg's self-propelled artillery (the tank at the end of chapter 11).

Herb + Chem Fluid

Takes 2 slots. The Duke sells it for 1,000 Lei: crafting it is free, so save every Herb and Chem Fluid for this. In the red, back off before healing: near death your health creeps back up to yellow on every difficulty. Free scripted heals: on entering the castle and during House Beneviento. On Village of Shadows the Duke stocks 99. The challenge "Don't Trust That Snake Oil" (35,000 CP) asks you to finish the story using four or fewer recovery items (the LZ Answerer's green mode does not count).