Have had it twice - got it in Nepal and got in in Mexico. In Nepal, there is over-the-counter medication available (Tinidazole) that was very effective and quick. after getting home from Mexico, I found that my doctor was reluctant to treat me with medication until we got a positive test from a stool sample. Several attempts later, no positive tests. Since I had had it before I was familiar with the symptoms and was pretty sure it was the same deal. Both my wife and I were not getting any better, so we contacted a specialist who told us the stool samples hardly ever come back positive. and was sure from the symptoms that we had Giardiasis, and prescribed the usual treatment here isn the US (Flagyl at that time). It was unpleasant but effective. It's not uncommon for Giardiasis to stick with you at a low level: you think you've gotten rid of it, but then when your body comes under stress (like your next strenuous trip to the mountains) it comes back. So I would not leave it untreated If I got it again.