How do you use health items in Borderlands 2?

I played Borderlands 1, but it's been a long time. I've searched through the menus, and I can't see how I use any of the red health items. I know I must have some, because when I approach new ones they say "Full". Help?


Solution 1:

The health items are instantly applied in Borderlands 2 (unlike Borderlands 1, where there were some medkits that had to be applied from the inventory). They're useless if you're already at full health.