I believe the BA is more useful if the vial sits for awhile after reconstituted (in the fridge). It keeps bacteria from growing inside the vial. I would think that sterile water would be fine by itself if it was used as soon as the hgh was reconstituted. (One time use) or maybe even a day or two after as well. I wouldn’t let it sit for a week or longer without BA. But that’s just my personal beliefs. In short, if you run a vial every couple of days then I’d think sterile water alone is fine. If you run a vial a week I’d use bac water, just to be safe.... generally speaking.