DeniseRN_TPA said:

Dead space is the answer to the missing dose.

Sharing my dosing arithmetic titration experience with compounded semaglutide — I have been tracking injection volumes meticulously:

Using 5mg/2mL concentration with 1cc insulin syringes:

• Month 1: 10 units (0.25mg) — mild appetite reduction
• Month 2: 20 units (0.5mg) — significant appetite suppression
• Month 3: 30 units (0.75mg) — custom intermediate dose
• Month 4: 40 units (1.0mg) — optimal for me, staying here

The beauty of compounded vials is you can do custom intermediate doses. My provider was great about tailoring to my response.

One thing that is still open after Dr.GutHealth’s answer:

How to check the arithmetic without trusting a website calculator, since three calculators gave me three answers?

BethLabQueen said:

Sharing my dosing arithmetic titration experience with compounded semaglutide — I have been tracking injection volumes meticulously: Using 5mg/2mL…

Quick syringe math for dosing arithmetic dosing: if your vial is reconstituted at 5mg/2mL, that's 2.5mg/mL. For a 0.25mg dose you need 0.1mL = 10 units on an insulin syringe.

I keep a chart on my fridge:

• 0.25mg = 10 units
• 0.5mg = 20 units
• 1.0mg = 40 units
• 1.25mg = 50 units

Always double-check your concentration before drawing up!

Closing the loop on my own question.

Resolved. I wrote mg, ml and mg/ml on the vial in marker and did the division in that order, and the two of us now get the same number every time.

Dr.LipidDallas said:

Quick syringe math for dosing arithmetic dosing: if your vial is reconstituted at 5mg/2mL, that's 2.5mg/mL.

Agreed, and it is worth saying that rounding to the nearest whole unit is usually acceptable at maintenance doses and is not acceptable at the bottom of a ladder, where one unit can be a fifth of the intended dose.