Quick Answer
Units on an insulin syringe measure volume, not milligrams of semaglutide. On a standard U-100 syringe, 100 units equal 1 mL. To convert, you need the concentration printed on your vial label: mg = (units ÷ 100) × concentration in mg/mL. Example: 20 units from a 2.5 mg/mL vial is 0.5 mg of semaglutide. Concentrations vary between pharmacies and prescriptions, so no chart on the internet, including this one, overrides your own pharmacy label and your prescriber's instructions. Your prescriber sets your dose; this page only explains the math.
Why Semaglutide Is Measured in Units at All
Brand-name semaglutide (Wegovy, Ozempic) comes in pre-filled pens with fixed, labeled doses, per the FDA labels for those products. Compounded semaglutide, prepared for an individual patient by a state-licensed compounding pharmacy (section 503A) under a physician's prescription, is usually dispensed as a vial, and you draw each dose with a U-100 insulin syringe.
U-100 syringes are marked in units because they were designed for insulin. The marking is pure volume:
The syringe has no idea what liquid is in it. That is why the same unit count can mean very different milligram doses from different vials.
Compounded semaglutide is not FDA-approved as a final product and is not a generic version of, or interchangeable with, the brand-name pens. Doses do not transfer between products, or between vials of different concentrations, without your physician's direction.
The Conversion Formula
Two directions, one piece of required information (your vial's concentration in mg/mL, printed on the pharmacy label):
*Units to mg:*
mg = (units ÷ 100) × concentration (mg/mL)
*mg to units:*
units = (mg ÷ concentration) × 100
Example both ways with a 2.5 mg/mL vial:
Conversion Chart by Vial Concentration
The doses in the left column mirror the weekly dose levels used in the titration schedule of the FDA-approved brand product (Wegovy climbs from 0.25 mg to 2.4 mg per week per its label). Your prescriber may use different doses; this chart is math, not a dosing recommendation.
| Dose | 1 mg/mL vial | 2.5 mg/mL vial | 5 mg/mL vial |
|---|---|---|---|
| 0.25 mg | 25 units | 10 units | 5 units |
| 0.5 mg | 50 units | 20 units | 10 units |
| 1.0 mg | 100 units | 40 units | 20 units |
| 1.7 mg | 170 units* | 68 units | 34 units |
| 2.4 mg | 240 units* | 96 units | 48 units |
*More than 100 units exceeds a 1 mL syringe. If your instructions ever imply drawing more than one full syringe, stop and call your pharmacy; in practice, higher doses are dispensed at higher concentrations so the volume stays small.
Read the chart in one direction only: find your vial's concentration first, then your prescribed dose. Using the wrong column is the classic error, and it changes the dose by 2 to 5 times.
The Five Rules That Prevent Dosing Errors
1. Your pharmacy label is the final word. Concentration varies between compounding pharmacies and can change between refills. Re-read every new vial. 2. Your prescriber sets the dose. Titration decisions (when to increase, whether to stay longer at a step) belong to your physician, not to a schedule you found online. See our semaglutide dosage chart guide for how physicians typically structure titration. 3. Never reuse someone else's units. A friend's 25 units may be a completely different milligram dose than your 25 units. 4. Confirm after any change. New pharmacy, new concentration, new syringe size: one message to your care team before the next injection. Our clinicians are listed on the care team page. 5. When in doubt, do not inject. A skipped dose while you wait for your pharmacy to confirm is far better than a guessed one. If you take too much semaglutide, contact your prescriber or Poison Control (1-800-222-1222) right away.
Common Mistakes We Want You to Avoid
The Bottom Line
Semaglutide units-to-mg conversion is one formula: mg = (units ÷ 100) × your vial's concentration in mg/mL. The formula is easy; the discipline is what protects you. Check the label on every vial, follow the dose your prescriber set, and call your pharmacy the moment anything does not line up. If you are considering physician-supervised semaglutide treatment where dosing instructions come with the vial and a clinician you can message, that is exactly how our program is built. Learn more in our compounded semaglutide guide.
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This article is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider. Never change your dose or perform a dose conversion on your own; your prescriber's instructions and your pharmacy label are the final authority. Compounded medications are not FDA-approved as final products. Individual results may vary.
Frequently Asked Questions
How many units is 0.25 mg of semaglutide?
It depends entirely on your vial's concentration. On a standard U-100 insulin syringe, 0.25 mg equals 10 units if the vial is 2.5 mg/mL, 25 units if it is 1 mg/mL, and 5 units if it is 5 mg/mL. There is no universal answer, which is why you must use the concentration printed on your own pharmacy label and the instructions from your prescriber, never a number from a forum or a friend.
How many units is 1 mg of semaglutide?
On a U-100 insulin syringe, 1 mg of semaglutide is 40 units at a concentration of 2.5 mg/mL, 100 units at 1 mg/mL, and 20 units at 5 mg/mL. Check the concentration on your vial label and confirm the unit count with your pharmacy or prescriber before drawing a dose.
Is 1 unit of semaglutide the same as 1 mg?
No. A unit on a U-100 insulin syringe is a volume measurement: 1 unit equals 0.01 mL of liquid. How many milligrams of semaglutide that volume contains depends on the vial's concentration. Confusing units with milligrams is the single most common conversion mistake, and it can lead to a dose that is several times too high or too low.
Why did my unit count change after switching pharmacies or refills?
Because compounded semaglutide concentrations vary between pharmacies and sometimes between prescriptions. If your previous vial was 2.5 mg/mL and your new vial is 5 mg/mL, the same milligram dose is half the units. This is why you should never carry over a unit count from an old vial: re-read the label on every new vial and confirm the draw with your pharmacy or prescriber if anything changed.
Do Wegovy and Ozempic pens use units?
No. Brand-name Wegovy and Ozempic come in pre-filled, fixed-dose pens: you dial or use the labeled dose in milligrams and the pen delivers the measured amount, per the FDA labels for those products. Unit-based dosing with an insulin syringe applies to compounded semaglutide dispensed in vials. Compounded semaglutide is not FDA-approved as a final product and is not a generic version of, or interchangeable with, the brand pens, and the doses are not directly transferable between products without your physician's direction.
What should I do if my syringe markings do not match my instructions?
Stop and call your pharmacy or prescriber before injecting anything. Do not guess, do not average, and do not use someone else's conversion. Mismatches usually mean a different syringe size (U-100 syringes come in 0.3 mL, 0.5 mL, and 1 mL versions), a different concentration than expected, or instructions written for a previous vial. Each is resolved with one phone call.
Majesta Health medical content is written against primary sources (FDA labels, peer-reviewed trials, HHS and CDC publications) and passes a documented compliance review before publication. We are rolling out named physician review with US-licensed clinicians from our partner MD Integrations (MDI): each reviewed article will show the reviewing physician's name, NPI, and review date. MDI is LegitScript certified and SOC 2 Type II accredited.
- US-licensed physicians affiliated with our clinical partner MD Integrations (LegitScript certified, HIPAA, SOC 2 Type II, ISO certified)
- Board-certified in primary care and obesity medicine
- Active state medical licensure required for every prescribing clinician
- Active DEA registration where applicable (note: GLP-1 medications are not controlled substances)
- Telehealth practice across the states we currently serve through the MD Integrations Medical Services Organization (coverage varies by state; see our states page)
- Dispensing pharmacy partner: Belmar Pharma Solutions (LegitScript certified, NABP accredited); Majesta prescriptions are dispensed through Belmar's state-licensed 503A compounding pharmacy