Brand Mounjaro comes in a pre-filled pen. If you are drawing tirzepatide with a syringe, you are using a vial: a Zepbound single-dose vial or a compounded multi-dose vial. The steps are the same either way. Check the strength on the label. Draw your units on a U-100 insulin syringe. Clean a spot on the belly, thigh or upper arm. Inject under the skin. Drop the syringe in a sharps container. If you are new to the drug, start with our tirzepatide guide, then follow the steps below.
Key takeaways
- Mounjaro pens need no syringe. Syringe injections are for vials, and compounded tirzepatide is the usual reason someone is drawing from a vial.
- Units come from the vial concentration: at 10 mg/mL, 2.5 mg is 25 units, 5 mg is 50 units, 15 mg is 150 units (two draws).
- Labeled sites are the abdomen, thigh and upper arm. Rotate every week.
- The label dose schedule applies regardless of device: 2.5 mg once weekly for 4 weeks, then 2.5 mg steps after at least 4 weeks each, up to 15 mg.
- Compounded tirzepatide is not FDA approved and is not interchangeable with Mounjaro or Zepbound.
Pen versus vial and syringe
| Product | Device | Dose measuring | Sites |
|---|---|---|---|
| Mounjaro (brand) | Single-use pen, hidden needle | Fixed dose per pen; no math | Abdomen, thigh, upper arm |
| Zepbound (brand) | Single-use pen, or single-dose vial with a syringe | Fixed per pen or per vial | Abdomen, thigh, upper arm |
| Compounded tirzepatide | Multi-dose vial, U-100 insulin syringe | You draw units based on the vial's mg/mL | Abdomen, thigh, upper arm |
Source: Zepbound and Mounjaro prescribing information (dosage forms and administration); compounded product per the dispensing pharmacy.
Step 1: convert your dose to units
A U-100 insulin syringe reads in units, and 100 units equals 1 mL. Divide your dose in mg by the concentration in mg/mL to get mL, then multiply by 100. The concentration is on the vial label and can differ between vials. This table uses 10 mg/mL as the example; at 5 mg/mL double the units, at 20 mg/mL halve them.
Check your GLP-1 eligibility
Use our free BMI Calculator to see if you may qualify for provider-reviewed GLP-1 therapy.
Try the BMI Calculator →| Weekly dose | mL at 10 mg/mL | Units at 10 mg/mL |
|---|---|---|
| 2.5 mg | 0.25 | 25 |
| 5 mg | 0.5 | 50 |
| 7.5 mg | 0.75 | 75 |
| 10 mg | 1.0 | 100 |
| 12.5 mg | 1.25 | 125 (two draws) |
| 15 mg | 1.5 | 150 (two draws) |
Source: arithmetic from the labeled strengths and the U-100 standard. The concentration on your vial controls; confirm with the pharmacy.
Every concentration is on the tirzepatide dosage chart, and the calculator does the math for your own vial. If your vial arrived as a powder, mix it first using the pharmacy's water volume; see how to mix tirzepatide powder.
Step 2 to 6: draw and inject
| Step | What to do | Why |
|---|---|---|
| 2. Set up | Wash hands. Lay out the vial, a new syringe, alcohol swabs and a sharps container. Check the vial label for concentration and beyond-use date. Look at the liquid: clear, no particles. | The label says not to use a solution with particles or discoloration. |
| 3. Prepare the vial | Wipe the rubber top with alcohol and let it dry. Pull the plunger to your unit mark to fill the syringe with air, push the needle through the stopper, and push the air into the vial. | Air in equalizes pressure so the liquid draws smoothly. |
| 4. Draw the dose | Turn the vial upside down with the needle in it. Pull the plunger slowly to your unit mark. Tap the syringe so bubbles rise, push them back into the vial, and re-check the mark. | Bubbles displace medication and make the dose short. |
| 5. Inject | Clean the site and let it dry. Pinch a fold of skin if your pharmacy advises, insert the needle straight in, push the plunger all the way, hold a few seconds, withdraw. | Subcutaneous injection into the fatty layer, per the label. |
| 6. Finish | Do not recap. Drop the syringe in the sharps container. Return the vial to the fridge. Note the date and site. | Prevents needle injuries and keeps rotation on track. |
Source: general subcutaneous technique consistent with the Zepbound and Mounjaro prescribing information; your pharmacy's directions control where they differ.
If you want to see it done, the video embedded on this page walks through a syringe injection, and the Zepbound pen video covers the pen for comparison.
Mounjaro injection sites
The label lists three: the abdomen, the thigh and the upper arm. It says to rotate and does not rank them. Rotation means a different site or a different area within the site each week; a simple pattern is abdomen left, thigh right, abdomen right, thigh left. Site details and a rotation chart are on where do you inject tirzepatide.
How to inject Mounjaro or tirzepatide in the belly
Sit or stand comfortably. Choose a soft area of the abdomen away from the navel, any scar, and the line where your waistband sits. Clean it with alcohol and let it dry. Pinch a fold of skin between thumb and fingers if your pharmacy has told you to, insert the needle straight into the fold, push the plunger fully, wait a few seconds, and withdraw. Do not rub the spot. Next week, use the other side of the abdomen or move to the thigh. Skip any area that is bruised, hard or still red from the last shot.
Common syringe mistakes
| Mistake | Result | Fix |
|---|---|---|
| Reading mg as units | 5 units instead of 50 units at 10 mg/mL: a tenth of the dose | Always convert with the concentration |
| Using last vial's unit count on a new vial | Double or half the dose if the concentration changed | Read every label |
| Skipping the air step | Hard to draw; bubbles | Inject air equal to your dose first |
| Injecting through wet alcohol | Stinging | Let it dry |
| Same spot every week | Irritation, injection site reactions | Rotate sites |
| Recapping the needle | Needle-stick injury | Straight into sharps |
Source: arithmetic and standard injection practice; injection site reactions are a listed common adverse reaction on the Zepbound label.
Storage and timing rules that apply to syringe users
Keep the vial at 2 to 8 C, do not freeze it, and protect it from light. Brand product may sit unrefrigerated at up to 30 C for up to 21 days; a compounded vial follows its pharmacy beyond-use date. Inject once weekly on the same day. A missed dose can be taken within 4 days; after that, skip it. Never take two doses within 3 days of each other. Dose increases of 2.5 mg happen only after at least 4 weeks on the current dose and only when your prescriber says so.
What this means for compounded tirzepatide
Syringe injection exists because compounded tirzepatide comes in a vial. Compounded tirzepatide is not FDA approved and is not interchangeable with Mounjaro or Zepbound; a licensed provider decides whether it is appropriate. At FormBlends, injection supplies are included, medication is compounded by state-licensed 503A compounding pharmacies and shipped cold-chain, and compounded tirzepatide is $149 for the first month, then $239 a month, or $214 a month with Subscribe & Save, at any dose. See pricing or begin at start.
Frequently Asked Questions
How do I inject Mounjaro with a syringe?
Brand Mounjaro is a pen and does not use a syringe. If you have tirzepatide in a vial, convert your dose to units using the vial's concentration, draw it on a U-100 insulin syringe, and inject under the skin of the abdomen, thigh or upper arm.
Is there a video on how to inject Mounjaro with a syringe?
Yes. The video embedded on this page shows a syringe injection of a GLP-1 medication step by step, and the steps above match it. Your pharmacy's written instructions take priority where they differ.
What are the Mounjaro injection sites?
The abdomen, the front of the thigh and the back of the upper arm. Rotate weekly. The label does not name a best site.
How do I inject Mounjaro in the belly?
Pick a soft spot away from the navel and waistband, clean it, let it dry, pinch if advised, insert straight, push the plunger fully, and withdraw. Use a different area next week.
How many units is my tirzepatide dose?
At 10 mg/mL: 25 units for 2.5 mg, 50 for 5 mg, 75 for 7.5 mg, 100 for 10 mg, 125 for 12.5 mg and 150 for 15 mg. Other concentrations change the count, so check your vial.
Sources
- Mounjaro (tirzepatide) prescribing information, Eli Lilly via DailyMed, revised 08/2026.
- Zepbound (tirzepatide) prescribing information, Eli Lilly via DailyMed, revised 08/2026.
- Mounjaro US prescribing information (PDF), Eli Lilly, 2026.
- FormBlends pricing, Form Blends LLC, verified September 5, 2026.
Next steps
Keep the tirzepatide dosage chart by your vial and read tirzepatide needle size if you have syringe options. Browse the tirzepatide hub for every other tirzepatide question. Ask a clinician or pharmacist to watch your first injection if you are unsure. Compounded tirzepatide is not FDA approved and is not interchangeable with Zepbound or Mounjaro; a licensed provider decides whether it is appropriate for you.
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