The main thing that made the GI Dr have us have the sweat test done was the weight loss ( he is 14 months and 14lbs he was almost 16lbs at 10 months) He has always struggled with his weight especially when we tried adding more fat and calories it seam to make him lose more weight, the mucus in the poop and the 3 infections in 1 month requiring antibiotics 3 different times.