Vial sizes & concentrations — the chart that turns mg/mL into a safe draw
Updated 2026-08-10 — rebuilt with the conversion charts the questions actually ask for: what's in a vial, how many mL, and how concentrations turn into syringe units.
A vial label answers three different questions, and mixing them up is the root of most dosing errors. How much liquid? That's volume, in mL — common compounded GLP-1 vials hold 1, 2, 2.5, or 3 mL. How strong? That's concentration, in mg/mL. How much drug total? Volume × concentration — a "10 mg vial" might be 1 mL at 10 mg/mL or 2 mL at 5 mg/mL, identical totals with completely different syringe draws. Doses are prescribed in mg; insulin syringes read units (100 units = 1 mL); the label's concentration is the only bridge between them.
The conversion chart: dose × concentration → mL → units
| Your dose | at 2.5 mg/mL | at 5 mg/mL | at 10 mg/mL | at 12.5 mg/mL |
|---|---|---|---|---|
| 2.5 mg | 1 mL · 100 u | 0.5 mL · 50 u | 0.25 mL · 25 u | 0.2 mL · 20 u |
| 5 mg | 2 mL · 200 u | 1 mL · 100 u | 0.5 mL · 50 u | 0.4 mL · 40 u |
| 7.5 mg | — | 1.5 mL · 150 u | 0.75 mL · 75 u | 0.6 mL · 60 u |
| 10 mg | — | 2 mL · 200 u | 1 mL · 100 u | 0.8 mL · 80 u |
Formula behind every cell: prescribed mg ÷ label mg/mL = mL; × 100 = units. The dangerous pattern is volumetric habit — repeating last month's units after the concentration changed — which is why the worked double-dose example is required reading before any refill.
"Ozempic vial": what people actually mean
In the U.S., brand semaglutide ships as pens — Ozempic and Wegovy are multi- or single-dose pen injectors, not vials — so an "Ozempic vial" is almost always a compounded semaglutide vial being described loosely (and "compounded Ozempic" isn't a real product either; the compounded drug is semaglutide). Tirzepatide is the exception where brand vials genuinely exist: Zepbound single-dose vials at the 2.5 and 5 mg starter tiers ship via LillyDirect's $299–$399 self-pay program. If a seller offers "Ozempic in a vial," you're being offered a compounded product — apply the pharmacy-verification workflow before anything else.
Vial size, price, and the beyond-use clock
Bigger vials aren't automatically better value: a large multi-dose vial still dies at its beyond-use date, so dispensed volume beyond what you'll inject before the BUD is paid-for waste. The pricing pages normalize this into effective monthly cost; the practical habit is four label reads on every shipment — concentration, volume, BUD, storage — then the one-line math above, written down before the first draw. Field pricing context: semaglutide from $145 and tirzepatide from $186 effective.
Frequently asked questions
How much is in a vial?
Two answers on every label: volume (commonly 1–3 mL for compounded GLP-1s) and total drug (volume × concentration). A '10 mg vial' can be 1 mL at 10 mg/mL or 2 mL at 5 mg/mL — same total, different draws.
How many mL are in a GLP-1 vial?
Typically 1, 2, 2.5, or 3 mL for compounded semaglutide and tirzepatide — but the label governs. Milligrams of drug come from mL × mg/mL, not from vial size alone.
How do I convert my dose to syringe units?
Prescribed mg ÷ label concentration (mg/mL) = mL; multiply by 100 for units on a U-100 insulin syringe. Recompute on every fill — concentrations change between vials.
Does Ozempic come in a vial?
Not in the U.S. — Ozempic and Wegovy are pens. Vials of semaglutide are compounded products. Brand tirzepatide does offer Zepbound single-dose vials (2.5/5 mg) via LillyDirect at $299–$399.
What are common semaglutide vial sizes?
Compounded programs commonly dispense 1–3 mL vials at concentrations like 2.5 or 5 mg/mL. Size and concentration vary by pharmacy, which is exactly why the label math must be redone every shipment.