Reconstitution calculator
Mixing a powder with water changes nothing about the amount in the vial. It changes the concentration, and therefore how much liquid holds a given amount. Getting that arithmetic wrong is the most common way someone ends up taking ten times what they intended. This page shows the working, so the number can be checked.
How the arithmetic works
Concentration is the amount in the vial divided by the water added. A 5 mg vial with 2 mL of water gives 2.5 mg per mL, which is 2,500 mcg per mL.
Volume to draw is the dose divided by the concentration. A 250 mcg dose at 2,500 mcg per mL is 0.1 mL.
Insulin units are the part that catches people out. A U-100 syringe has 100 units per mL, so 0.1 mL is 10 units. The marks on the barrel measure volume, not the amount of compound, so the same 10 units holds a different amount every time the mixing changes.
What this page does not do
It does not tell you what to take, how often, or whether to take anything at all. It converts numbers you supply. The amount per dose has to come from somewhere, and for an unapproved compound there is often no established human dose to come from. Where the book reports a range, it reports what was used in a cited trial or what is commonly reported, and says which of the two it is.
Edition 1.0. Not medical advice. Sterile technique, storage and expiry matter as much as the arithmetic, and a clinician is the right person to discuss any of it with.