I don't know about his heart medication. Barb may chime in here. But basically the only difference between powder and liquid is 1 cc of fluid. So if you have powder, you would add 1 cc to the basic 29 cc of fluid you add to 10,000 iu. I would not do 250 iu 2x a day though. Quite a few people have hunger on a dose that high. The standard is 166 iu which is .5 with it mixed the standard way. If you're determined to try the higher dose, I would put less fluid in it though so you don't have so much to hold under the tongue. Stevia in the mix would just be nasty and it might mess up the hcg. It's very fragile. You should refrigerate your unopened vials of hcg.