Originally Posted by xhunterrrr
You have to buy them (or find them to pick up) if you run out of them. You only carry 3 at a time.
I think he's talking about the skill you earn that lets you do it. In Far Cry 3 it was a skill that let you heal without actually using medpacks. You would do an animation where you bandaged yourself up or relocated your joints in your hand. It didn't fill you up completely but it did help.