Key Takeaways
- Units on a U-100 syringe measure volume: 100 units is one milliliter.
- Your dose in milligrams depends on your own vial's concentration, so the same unit mark can mean different amounts in different vials.
- Approved tirzepatide schedules start low and step up gradually, which helps your body adjust.
- Your provider writes your schedule and changes it with you as you go.
Matching the numbers on your prescription to the marks on your syringe can be confusing at first. The medicine behind those numbers acts on two appetite signals, GIP and GLP-1, and in a six-week study it reduced hunger before meals and food cravings. One number on your vial's label, its concentration, connects your units to your milligrams.
What Is a "Unit" of Tirzepatide?
It's a mark on your syringe, and it measures how much liquid you draw up.
The marks come from insulin. A U-100 syringe is marked for a solution containing 100 units per milliliter, which is what U-100 on an insulin vial means. So each unit mark is one hundredth of a milliliter, whatever liquid you draw into it.
From Units to Milliliters
| Units on a U-100 syringe | Volume drawn |
|---|---|
| 5 units | 0.05 mL |
| 10 units | 0.10 mL |
| 15 units | 0.15 mL |
| 20 units | 0.20 mL |
| 25 units | 0.25 mL |
| 30 units | 0.30 mL |
| 40 units | 0.40 mL |
| 50 units | 0.50 mL |
To get milligrams, multiply the volume by your vial's concentration in mg/mL. Both numbers are printed on your own label. Only your label shows your vial's strength, which is why this chart stops at milliliters.
Reading Your Units
A unit tells you how much liquid you draw, not how much medicine.
The Same Mark Is Not the Same Dose
Twenty units from one vial and twenty units from another can be different amounts of tirzepatide. A compounded preparation is made for one person by a licensed pharmacy, so two vials of the same drug can differ in strength.
Someone Else's Units Won't Tell You Your Dose
If someone tells you how many units they take, ask what concentration their vial is. Without that, their number can't tell you anything about your own dose.
Approved Pens Deliver a Set Dose
With an approved pen, there are no units to read. If you use approved Zepbound vials, you draw each dose up with a syringe, and the Zepbound label gives each vial dose in milliliters, with the strength printed on the vial. Either way, follow the instructions that come with your prescription.
UNITS ARE VOLUME
Milligrams need one more number.
- Units on a U-100 syringe the syringe's own graduation, from approved insulin labeling
- Hundredths of a milliliter 100 units is 1 mL
- Volume, times your vial's mg/mL both numbers are printed on your own label
This is arithmetic, not a recommendation. What you should be taking comes from your prescriber.
Why Does the Schedule Change by Week?
Because approved tirzepatide starts at a low dose and steps up at fixed intervals, not by how you feel.
The Zepbound label sets a starting dosage to begin treatment and states plainly that it is not approved as a maintenance dosage. The diabetes product's labeling works the same way, with a period at the starting dosage before any increase is considered.
Starting low gives your body time to adjust, because stomach side effects such as nausea are most common early on.
Your provider writes your own schedule, for the strength printed on your vial.
Side Effects and What to Tell Your Provider
The most common side effects listed on the Zepbound label are stomach-related: nausea, diarrhea, vomiting, constipation, abdominal pain and indigestion.
Tirzepatide isn't right for everyone. Your provider will ask about:
- Thyroid history: a personal or family history of medullary thyroid cancer or MEN 2.
- Past conditions: pancreatitis, gallbladder disease or kidney problems.
- Other medicines: especially diabetes medicines that can lower blood sugar.
- Allergies: any serious allergic reaction to a medicine.
Let your provider know right away about severe or lasting stomach pain, ongoing vomiting or signs of dehydration.
When This Chart Does Not Apply
Ask your provider or pharmacy instead of a chart when:
- Your vial's concentration isn't printed clearly. Ask the pharmacy. Don't infer it from anything, including a previous vial.
- You use a pen. It gives a set dose, so there are no units to convert.
- You'd like to change your schedule. Your prescriber makes that call with you, including any pause or a longer stay at one step.
- You missed a dose. Ask your provider what to do, because the answer depends on your prescription.
The compounded tirzepatide guide explains how a compounded preparation is made, and the injection-site guide covers where it goes.
At an evaluation, a licensed provider reviews your health history and goals with you, then writes your prescription and your schedule.
Frequently Asked Questions
How many units of tirzepatide should I take?
It depends on two numbers, and only your prescriber and your own label have them: your prescribed milligram amount and your vial's concentration. A unit figure from anywhere else is missing the concentration it depends on.
How many units is one milliliter?
One hundred units on a U-100 syringe, the marking approved insulin labeling describes. The marks belong to the syringe, so this holds whatever liquid you draw into it.
Why do two people take different units for the same dose?
Because their vials are at different concentrations. Milligrams equal volume multiplied by concentration, so the same milligram amount lands on different unit marks when the mg/mL differs.
Is there a standard weekly chart for compounded tirzepatide?
No reviewed schedule exists for a compounded preparation, because there is no label to carry one. Your prescriber writes your schedule and revisits it with you.
Why does the dose start low?
To help your body adjust. In the Zepbound label's weight-management trials, 25% to 29% of adults taking it reported nausea, compared with 8% on placebo. Stomach side effects are most common in the early weeks, and starting low and stepping up gradually helps make that easier.
What does the boxed warning on Zepbound say?
The Zepbound label carries a boxed warning about thyroid C-cell tumors. A boxed warning is printed in a box at the start of a prescription label and covers its most serious risks. Tirzepatide caused these tumors in rats; it isn't known whether it does in people. Zepbound isn't for anyone with a personal or family history of medullary thyroid cancer or MEN 2, or a serious allergy to tirzepatide or its ingredients.
The label also says it isn't recommended for severe gastroparesis, and to tell your care team before any procedure with anesthesia or deep sedation. The label notes that routine blood tests (calcitonin) or thyroid ultrasound are of uncertain value for catching these tumors early, so tell your provider about a lump in your neck, trouble swallowing, shortness of breath or hoarseness that doesn't go away.
What results have people seen on approved tirzepatide?
In a large study of adults taking approved tirzepatide injections, people still on treatment lost an average of 5.9% of their starting weight at 3 months, 10.1% at 6 months and 15.3% at 12 months.
The study was real-world and observational, covering 18,386 matched adults receiving an approved tirzepatide or semaglutide injection (Rodriguez et al., JAMA Internal Medicine, 2024); 52% had type 2 diabetes. Each timepoint is a separate estimate, so they shouldn't be added together. The tirzepatide injection studied is approved for type 2 diabetes, so its use for weight management was off-label; the results concern approved injections rather than a compounded preparation, and individual results vary. Doses weren't verified, more than half of people stopped treatment during follow-up (52.5% of those on semaglutide and 55.9% on tirzepatide), and missing weights were estimated statistically.
What did studies find about hunger?
In a six-week study, adults who were overweight or living with obesity and took tirzepatide reported less hunger before meals and fewer food cravings than those taking a placebo. The study didn't test a compounded preparation, and results vary from person to person, so your provider will check in on how you're doing.
References
Rodriguez, P. J., Goodwin Cartwright, B. M., Gratzl, S., et al. (2024). Semaglutide vs tirzepatide for weight loss in adults with overweight or obesity. JAMA Internal Medicine, 184(9), 1056-1064. https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2821080
Tirzepatide on ingestive behavior in adults with overweight or obesity: A randomized 6-week phase 1 trial. (2025). Nature Medicine. doi:10.1038/s41591-025-03774-9. Read October 1, 2026. https://www.nature.com/articles/s41591-025-03774-9
Eli Lilly and Company. (2022). Humulin R (insulin human) injection, for subcutaneous or intravenous use: Prescribing information (revised June 2022), Dosage Forms and Strengths: 100 units/mL (U-100). DailyMed, U.S. National Library of Medicine. Read 2026-08-20. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b519bd83-038c-4ec5-a231-a51ec5cc291f
Eli Lilly and Company. (2026). Zepbound (tirzepatide) injection, for subcutaneous use: Prescribing information (revised 4/2026). DailyMed, U.S. National Library of Medicine. Read 2026-08-20. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=487cd7e7-434c-4925-99fa-aa80b1cc776b
Eli Lilly and Company. (2026). Mounjaro (tirzepatide) injection, for subcutaneous use: Prescribing information (revised 4/2026). DailyMed, U.S. National Library of Medicine. Read 2026-08-20. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d2d7da5d-ad07-4228-955f-cf7e355c8cc0
U.S. Food and Drug Administration. (2026). Compounding and the FDA: Questions and answers. Read 2026-08-20. https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers
U.S. Food and Drug Administration. (2024). Frequently asked questions about labeling for prescription medicines. Content current as of April 1, 2024; read 2026-10-08. https://www.fda.gov/drugs/fdas-labeling-resources-human-prescription-drugs/frequently-asked-questions-about-labeling-prescription-medicines
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