DD didn't start to gain weight well until we switched to Zenpep. We also add Duocal powder to her Pediasure (have been doing so since under a year of age). What has really helped her is Pediasure 1.5 (350cals per 8oz) but I know Hazel isn't ready for that yet! <img src="i/expressions/face-icon-small-sad.gif" border="0"> Her dietician suggested an antacid when she wasn't gaining well, but we've been able to avoid it thus far. Each individual is different - even down the type of enzyme formulation that works for them. We tried Creon and her BMs shot up to 6x daily. With Zenpep, she has 1-2 BMs daily. We saw a lot BM variation when she was on Pancrease, but now she's - uh, regular.