Collecting medi-gel in Mass Effect 2 and 3 is very similar to the original game, but it's slightly less necessary because of its more passive role. Collecting medi-gel is still an important task, but its functionality is shifted to being used more for reviving downed teammates than topping off the player's HP. This system is more in line with other shooters and frees up the healing button from the previous game for other uses. Now, instead of a button press, simply wait behind cover after taking damage to restore health using medi-gel. Mass Effect 2 and 3 change medi-gel from being an active part of gameplay to a more passive one. To heal, simply press the 'Y' button on Xbox controllers, 'Triangle' on the PS4 or 'V' on PC.
Keep an eye out for the red medical kits when health gets low. Containers are something of a mixed back when looking for the healing item, however, certain containers are marked red and called 'medical kits' which always hold the item. Finding medi-gel is a little random, but the drop rate is relatively high off of enemies. It can be acquired by exploring each area and searching containers or by defeating enemies.
In the original Mass Effect, medi-gel is an item found in containers all throughout the world.
