Hello everyone,
I just unlocked this achievement a few minutes ago, using a method I was testing. The description says 'Complete a single player mission without using a Medikit or Bandage', okay, but can we die and getting the ach? The answer is YES.
I was on my way, mission 1, to do this fair, without using a Medikit or Bandage. But some enemies did kill me and I respawned quite at the same spot I died, just a few seconds earlier. The checkpoints in this game are very generous, we don't lost minutes of progression if we die. We almost respawn where we died, but just a few seconds earlier.
I think I died 3 times before reaching the end of the mission, and my assumption, test, my guess proved me right as the achievement popped and the debriefing screen.
So dying is not an obstacle. Take the time you want/need, die as many times as you want, but just don't use a Medikit or Bandage. I played almost the entire mission with just one unity of life. The screen gets a little darker as you're very injured, but we still can see clearly and react fine, it doesn't put a big handicap playing wounded.
And last point to confirm my method is that on mission 1 (I don't know for other levels), when we press start to pause the game and check some infos about the mission, in the challenges section I had the one named after the achievement: 'not using a Medikit or Bandage'. Toward the end of the level, I still had zero of those used, even though I died 3 times before.
This method makes this achievement a piece of cake, as long as you don't play a mission on difficulties where checkpoints are unavailable, making it harder if you restart at the very beginning if you die... During my run, I was on normal difficulty.
I hope this solution will help you. Take advantage of this trick to retrieve all the documents and make all the secondary objectives of the mission and thus cumulate several challenges/achievements including not using a Medikit or Bandage! ;-)