You can mix as much water as you want and the amount you use will determine the amount of IU's are in each unit of water. Think about it from a mathematic point of view. If the powder is 5000iu and you mixed it with 5ml of bac water, each 1ml of water will be 1000iu. See where I'm going with this? so if you mixed 5000iu with 2.5ml of water(half as much water) each .5ml of water would be 1000iu. If you have a vial large enough to mix 5ml of water in, it will be very easy to mesure your HCG. If you mix in 5ml, then each ml is 1000iu, so each .5ml is 500iu, and each .25ml is 250iu. If you are using 250iu 2x wk, through your cycle, you would inject .25ml of water (25 clicks on an insulin pin)

hope this makes sense bro!! A lot of guys get caught up on these measurements, so don't feel bad, but if you stop and think about it logically, its just simple math ;)