A 5 mg vial with 2 mL of water gives 2.5 mg/mL. On a U-100 insulin syringe each unit is 0.01 mL, so one unit holds 0.025 mg, or 25 mcg. A 250 mcg dose is therefore 10 units.

The part people get wrong is changing the water volume later. The vial strength is fixed; only the concentration moves. If you had used 1 mL instead, the same 10 units would have been 500 mcg.

I keep the arithmetic and my dose log in one place with the Peptide Tracker & Calculator, which also handles titration schedules.

Reconstitution. A vial's labeled strength is not a dose. Add the diluent, divide the total mass by the volume of water, and you have mg per mL. From there a dose in mL, and in insulin units, follows. Writing that ratio down at the moment you mix prevents most errors.

Titration as a history. Most protocols step up on a schedule. The useful record is the step history – what dose, for how long, and what happened – not just today's number.

Site rotation. Rotating injection sites is easy to lose track of after several weeks.

Expiry after puncture. Worth recording next to the reconstitution ratio, since both start on the same day.

Nothing here is medical advice; dosing decisions belong with your prescriber.