The med kit costs more to use depending on angle, and heaps more of there is an object in between.
Here are some pics of basic angle thing:
Both pictures are using the minimum TUs to use a med kit.
OK, by an object between (for taking even more TUs), I mean: In the diagonal picture, if an object was in the NE square from the south guy. I should have taken a pic for that too. Sorry. I think the extra TUs are also charged for using a stun baton in a similar situation.
Also: if you take a wounded soldier on a mission, you can heal hi up to full at the start. Doing that healing takes way more "ammo" out of the med kit than it should.