The mixing fluid it came with is most likely sterile water. Do not use this. This is designed for mixing and injecting the whole vial all at one time. Over time, the HCG will break down while it is in sterile water. You want to use Bacteriostatic water, which can be found online for cheap. Maybe $5-$10. If your vial is 5000iu, all you have to do is mix 2.5ml of bac water into your HCG vial. At this mix, 1/2ml of water is equal to 1000iu. So 1/4ml of water will be 500iu HCG. Easy!