Pharmacies in Warsaw by AcornMan
If, like about half the people in my group, you get some kind of illness during your visit, just look for the green signs that say "Apteka" on them. These are pharmacies, and you'll them all over the place. I was able to find good medication for my cold and cough and even discovered that you can buy codeine over the counter there (albeit in fairly small doses).
Of course, it would be easier if you just brought your own medicine just in case, but if you forget to do so don't worry because chances are you'll find what you need at an apteka without having to see a doctor first.