Far Cry 2

Yeah, achievement is buggy. Just completed the 3 in the north and it unlocked.

Ditto. 3 in the North :-)

I got it after 2 missions in the North and 3 in the South.
I read you get this achievement after completed 5 underground missions but it seems to be glitched regarding your comments.

I also got it after only 3 missions in the North. Just started about a week ago and figured this would've been patched by now. But once I walked out of the faction safehouse it popped.

Well, it's now 2012, and this hasn't been patched :D
I got it after only doing the three in the north. Just a heads up for newer people to the game, this could be easier than it already appears to be.

I got it after 3 in the north and 2 in the south.

Good solution. +1
If you are farming for suitcases (diamonds), it won't trigger indeed.

I got it after 3 in the north and 3 in the south.

I also only had 3 in the North and 2 in the South ... total! I thought that despite the achievement popping "early" I would still be prompted to do more pill missions later in the story in the South, but I never had to go back to the clinic. FWIW in the South I did all collectible cases, then convoys, then assassinations, then blitzed through the 6 faction missions and 4 final diamond-paid story missions. Only two calls back to the clinic during all of that.

Didn't pop early for me. Performed the Underground missions as soon as they appeared on the map. Notably, there was one occasion where I took the last pill in the bottle. As Bahaumaut mentioned, I was taking the pill as soon as symptoms arose, so this could have had an impact.

Same as Bahaumaut: grabbed all collectibles and finished every side mission possible before doing any main mission that wasn't required by the tutorial, then started on the main missions, had my Sickness level drop to zero, and this achievement popped after doing another Underground mission after the 6th main faction mission while still in the North. I suppose it's better to have the achievement glitched beneficially than making it extremely hard if not impossible to obtain due to a glitch.

This guide is incorrect. There are FOUR Underground locations in the north and four in the south as well. I got the achievement after three in the north so I can confirm it's still buggy as hell. You must have to play the game a ton to run out of pills to the point where you need more though. I only got three prompts in the north to go to Underground locations and only 2 in the south before the end. I have read that difficulty can play a role in how often the attacks happen as well.

Also got mine after 3 in the north and 2 in the south.

I got this after just 1 in the north and 2 in the south.

Little late, but 1 in the North and perhaps 2 in the South. I had an underground mission shown in the North but I couldn't access the building anytime so I left it and never ended up returning. Got my achievement anyway

Got mine after the 3rd in the north. Havent gone south yet.

I have only done two underground missions where I have had to deliver documents. I have just killed Prosper Kouassi. I have to now go and meet the reporter. Have I missed the opportunity to pick up the third underground mission. My last save is quite awhile back.

I dawdled in the North for a long while prior to getting past more than one Main Story mission so as to clear out all the collectibles. During this time, my Pill Bottle was basically infinite. After doing some story missions, I got the Underground missions opened up.

For me, the third mission up north, which occurred after my sixth story mission (which included idling to try and use up more malaria pills beforehand) unlocked this achievement. This was before even going south.

Notably, my Sickness Level went to 0 sometime between my idling, doing the 6th story mission, and then doing the 3rd Underground mission. I'm wondering if it has to do with your sickness level. Theory: Level 0 Malaria, and then perform an underground mission. And Malaria level might only drop if you repeatedly take a pill when the symptoms strike.