How to inject compounded tirzepatide from a vial
Medically reviewed by Kevin Brandstetter, M.D.Last reviewed September 28, 2026
Compounded tirzepatide comes in a multi-use vial. Once a week, you draw your dose into an insulin syringe and inject it under the skin of your stomach, thigh or upper arm. Doses are prescribed in milligrams but measured in syringe units, and the unit number depends on your vial's concentration, so recalculate with every new vial.
Before you start
Compounded tirzepatide is not FDA-approved and has not been reviewed by the FDA for safety, quality or effectiveness. By May 31, 2026, the FDA had received more than 730 adverse event reports linked to it, including reports of doses above the approved labels and faster increases. Because pharmacies set their own concentrations, write down four things before your first dose: concentration (mg/mL), prescribed dose (mg), the matching syringe units, and the beyond-use date. Tell your prescriber about thyroid cancer history or MEN 2, pancreatitis, gallbladder disease and diabetes medicines. If you use oral birth control, the approved tirzepatide label advises a backup or non-oral method for 4 weeks after starting and after each increase.
Step by step
Confirm the concentration on every vial
Read the label for strength (for example 10 mg/mL or 20 mg/mL), total volume, beyond-use date and storage directions. If the strength is different from your last vial, the same milligram dose now needs a different number of units. Stop and confirm that number before you draw anything.
Work out your units
Dose in mg divided by strength in mg/mL gives the volume in mL; multiply by 100 for U-100 syringe units. A 2.5 mg dose from a 10 mg/mL vial is 0.25 mL, or 25 units. From a 20 mg/mL vial it is 0.125 mL, or 12.5 units, a half-unit mark many syringes lack.
Look at the liquid, then clean the stopper
Hold the vial up to the light. Expect a clear solution with no specks, haze or ice. A vial that froze, or that arrived warm without the pharmacy clearing it, should not be used. Wash your hands and wipe the rubber stopper with a new alcohol swab, then let it dry.
Draw the dose accurately
Draw air to your unit line, push it into the vial, then invert the vial and pull the liquid slowly just beyond the line. Flick the syringe so air rises and press the plunger back to your exact unit mark. Read the mark at eye level, where the plunger's edge meets the scale.
Prepare the injection site
Use the stomach at least 2 inches from the belly button, the front of the thigh, or have someone else use the back of your upper arm. Pick a spot away from last week's. Wipe with alcohol and let it dry completely before inserting the needle.
Inject and wait 5 seconds
Gently pinch the skin, insert the needle as you were shown, and press the plunger at a steady pace to the bottom. Lilly's Mounjaro vial instructions advise keeping the needle in the skin for at least 5 seconds to deliver the whole dose; the same habit suits a compounded vial.
Discard and record
Put the syringe and needle straight into a sharps container without recapping, and never reuse them. Record the date, dose, units, vial strength and site. If a later vial has a different strength, that record shows at a glance that your unit number must change.
Schedule
Compounded tirzepatide is injected once a week, on the same day, at any time of day. With no FDA label, the dose plan comes from your prescriber. The approved tirzepatide labels start at 2.5 mg weekly and increase in 2.5 mg steps no sooner than every 4 weeks, to a maximum of 15 mg weekly for adults. The FDA has flagged reports of compounded doses above those limits. If you change your injection day, the approved label requires at least 3 days (72 hours) between two doses.
How and where to take it
Tirzepatide goes into the fat layer under the skin: the stomach area, the front of the thigh, or the back of the upper arm, which the approved label says another person should inject. On the abdomen, stay 2 inches clear of the belly button. Change the spot every week, even within the same area. The Mounjaro vial instructions warn that repeated use of one spot can cause pitted or thickened skin or lumps. Do not inject into skin that is tender, bruised, scaly, hard or scarred.
Storage
Follow your pharmacy's label, because storage depends on its formulation. Compounded tirzepatide vials are typically labeled for refrigeration at 36°F to 46°F, in the carton, away from light and the freezer section, and never frozen. The beyond-use date set by the pharmacy is the last day to use the vial, even if liquid remains. On delivery, open the box straight away and check the cold packs. If the contents feel warm or the packs are fully thawed, refrigerate but contact the pharmacy before injecting from that vial.
If you miss a dose
Compounded tirzepatide has no FDA label, so confirm the rule with your prescriber. A common reference is the approved tirzepatide label's rule: take a missed dose as soon as possible within 4 days (96 hours). If more than 4 days have passed, skip it and inject on your next regular day. Never take two doses within 3 days (72 hours) of each other, and do not draw a larger dose to catch up.
If you take too much
The FDA has received reports of dosing errors with compounded GLP-1 drugs from miscalculated doses; typical slips are drawing to the wrong line or using a previous vial's conversion. The FDA reports symptoms including nausea, vomiting, diarrhea, abdominal pain and constipation, sometimes needing medical care. If you think you took too much, call your prescriber or the Poison Help line at 1-800-222-1222. Seek emergency care if you cannot keep fluids down. Tirzepatide's half-life is about 5 days, so symptoms can persist.
What to avoid
Do not rely on memory for your unit number when a new vial arrives. Do not use a syringe other than the U-100 insulin syringe your conversion assumes, and never share vials or needles. Do not stack compounded tirzepatide with another GLP-1 or GIP/GLP-1 medicine. Plan backup contraception if you use the pill. Keep alcohol modest, especially with insulin or a sulfonylurea, and do not drive if you feel dizzy. Tell your care team before any procedure needing sedation.
Frequently asked questions
How many units is 2.5 mg or 5 mg of compounded tirzepatide?
It depends on your vial. At 10 mg/mL, 2.5 mg is 25 units and 5 mg is 50 units. At 20 mg/mL, 2.5 mg is 12.5 units and 5 mg is 25 units. The formula is dose in mg divided by mg/mL, times 100. Use our dose-to-units calculator, then confirm the result with your pharmacist.
Why can't I reuse last month's unit number?
Units measure volume, not medicine. If your new vial is twice as concentrated, the same number of units delivers twice the milligrams. The FDA has received reports of dosing errors from miscalculated doses with compounded GLP-1 products, and a concentration change is the easiest way for that to happen. Check the label every time.
Does the tirzepatide injection hurt?
Most people feel a quick pinch from the fine insulin-syringe needle. Letting the alcohol swab dry, relaxing the area, and injecting at a steady pace can help. Some people find a very cold dose stings more. The approved tirzepatide label lists injection-site reactions, so report pain, redness or itching that lasts, or a lump that does not settle.
Is bleeding or leaking after the injection a problem?
A small spot of blood or a drop of liquid is normal. Press with gauze or a cotton ball and do not rub. Frequent leaking often means the needle came out too soon, so hold it in for about 5 seconds after the plunger bottoms out. Bruising is more likely if you take blood thinners; mention it if it keeps happening.
What about air bubbles in the syringe?
Clear them before you inject. With doses as small as 12 or 25 units, a bubble can displace a meaningful share of the medicine. Point the needle up, flick the barrel so the air gathers at the top, push it out, and then recheck that the plunger edge sits exactly on your unit line.
How should I travel with compounded tirzepatide?
Keep the vial in your carry-on in an insulated pouch with a cold pack, cool but never frozen or touching ice directly. The approved pen's 21-day room-temperature allowance has not been established for compounded formulations, so ask your pharmacy what applies to yours. Bring syringes, swabs, a small sharps container and a copy of the prescription label.
Can I drink alcohol on compounded tirzepatide?
There is no specific rule for compounded tirzepatide. The approved tirzepatide label warns of low blood sugar when it is combined with insulin or a sulfonylurea, and alcohol can lower blood sugar further. It can also worsen nausea after a dose increase. Drink lightly, with food, and ask your prescriber what is sensible alongside your other medicines.
How do I switch from compounded tirzepatide to Zepbound or Mounjaro?
Only with your prescriber, who will pick the starting strength and date. Branded pens and vials are dosed in milligrams, so there is no unit conversion, but the device steps differ, so read that product's Instructions for Use first. Do not use leftover compounded vials alongside the branded product, and dispose of them safely.
Sources
- FDA's concerns with unapproved GLP-1 drugs used for weight loss (updated September 2026)
- Mounjaro (tirzepatide) prescribing information and vial Instructions for Use, DailyMed (NLM)
- Mounjaro prescribing information (Eli Lilly, revised August 2026)
- Compounding and the FDA: questions and answers
- Safe disposal of sharps, FDA
Compounded semaglutide and compounded tirzepatide are not FDA-approved generics of the brand-name products. A licensed 503A compounding pharmacy prepares each one for a single prescription.
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