Tirzepatide
Also called Mounjaro; Zepbound
An FDA-approved prescription peptide that activates both GIP and GLP-1 receptors. It lowers blood sugar and helps eligible patients lose weight. Mounjaro and Zepbound contain the same ingredient but have different approved uses.
Overview
What it is
A once-weekly dual GIP/GLP-1 receptor agonist. Mounjaro is approved for type 2 diabetes (with cardiovascular-risk language); Zepbound is approved for chronic weight management and related conditions.
How it works
It boosts insulin release when blood sugar is high, reduces excess glucagon, slows stomach emptying and reduces appetite. Semaglutide, by comparison, acts only on the GLP-1 receptor.
What the research shows
SURMOUNT-1 followed 2,539 adults without diabetes for 72 weeks; average weight loss was about 15% to 21% across dose groups versus about 3% with placebo. SURMOUNT-5 (751 adults) found 20.2% average loss with tirzepatide versus 13.7% with semaglutide at 72 weeks. In SURMOUNT-4, people who stopped and switched to placebo regained about 14% of body weight over a year, while those who continued lost a further 5.5%.
Studied for
- Type 2 diabetesapproved
- Chronic weight managementapproved
- Cardiovascular risk in type 2 diabetesapproved labeling
Safety and regulatory status
Safety and side effects
Common side effects are nausea, diarrhea, vomiting, constipation and stomach discomfort. It carries a boxed warning for thyroid C-cell tumors seen in rats and is contraindicated with a personal or family history of medullary thyroid cancer or MEN2. Other risks include pancreatitis, gallbladder disease, kidney injury from dehydration and low blood sugar with insulin. It can reduce oral contraceptive effectiveness; tell your anesthesia team before procedures.
Regulatory status
FDA approved (Mounjaro, Zepbound) as prescription pens and vials. Compounded and "research" tirzepatide are not FDA approved; FDA has warned about dosing errors and unapproved products.
Mixing and dosing reference
Reference information only. Read before using this section.
Tirzepatide (90 mg Vial) Dosage Protocol
- Vial
- 90 mg Tirzepatide
- Add diluent
- 2.25 mL
- Concentration
- 40 mg/mL
- 1 unit (U-100)
- 400 mcg in 0.01 mL
- Route
- Subcutaneous
- How often
- Once weekly by subcutaneous administration in the cited human trials.
- Typical range
- The cited programs evaluated target amounts through 15 mg weekly after stepwise escalation.
Standard Weekly Escalation Schedule
| Study Phase | Weekly Amount | U-100 Units | Volume |
|---|---|---|---|
| Weeks 1 to 4 | 2.5 mg | 6.25 units | 0.0625 mL |
| Weeks 5 to 8 | 5 mg | 12.5 units | 0.125 mL |
| Weeks 9 to 12 | 7.5 mg | 18.75 units | 0.1875 mL |
| Weeks 13 to 16 | 10 mg | 25 units | 0.25 mL |
| Weeks 17 to 20 | 12.5 mg | 31.25 units | 0.3125 mL |
| Weeks 21+ | 15 mg | 37.5 units | 0.375 mL |
How to mix
- Clean the vial stopper and gather the sterile supplies required by the research procedure.
- Add 2.25 mL of the documented sterile diluent slowly down the vial wall.
- Gently swirl or roll until dissolved. Do not shake.
- Label the vial 40 mg/mL with the preparation date and follow the exact product storage and discard instructions.
Dosing details
- The table converts one shared schedule for this vial concentration.
- Starting step: 2.5 mg once weekly for four weeks.
- Next step: 5 mg once weekly beginning at week 5.
- Additional steps: 7.5 mg, 10 mg, 12.5 mg, and 15 mg after at least four weeks at each amount when escalation is selected.
- Measurement: Use the units and mL displayed beside each weekly amount.
- Consistency: Vial size does not change the weekly schedule.
Storage
- Use the storage directions for the exact supplied formulation.
- Before preparation: Keep the vial dry, protected from light, and stored according to its documentation.
- After preparation: Refrigerate only as permitted by the exact formulation and diluent instructions.
- Labeling: Record the concentration, preparation date, storage conditions, and documented discard date.
- Handling: Avoid unnecessary agitation and follow the exact product instructions.
Administration technique
- General subcutaneous research technique should follow the approved institutional or laboratory procedure.
- Use a new sterile syringe and needle for every injection and each separate vial entry.
- Clean the vial stopper and selected site, then allow the surface to dry.
- Use the needle length, angle, and skinfold method specified by the governing procedure.
- Rotate sites systematically and document each administration.
- Place used sharps immediately in an appropriate sharps container.
Important notes
- Practical details for reading the schedule and vial calculations consistently.
- The weekly amounts are identical across every Tirzepatide vial-size page. Only concentration, volume, U-100 units, and supply totals change.
- The 2.5 mg amount is the four-week starting step. The cited maintenance targets are 5 mg, 10 mg, and 15 mg.
- Each increase is separated by at least four weeks in the current labeled escalation schedule.
- Use a new sterile syringe for each injection and place used sharps in an appropriate container.
- Record the weekly amount, calculated units, volume, date, and administration site consistently.
Protocol source: PeptideDosages.com
Common questions
Is tirzepatide better than semaglutide?
In SURMOUNT-5 average weight loss was greater, but individual response, tolerance and medical history still matter.
What happens if I stop?
Many people regain weight. Talk with your prescriber about a long-term plan.
Is a research vial the same as Zepbound?
No. Approved tirzepatide is a specific liquid product; research powders are not equivalent.
Related in Metabolic Health
Sources and further reading (6)
- DailyMed. Mounjaro and Zepbound prescribing information (checked Oct 2026).
- Jastreboff AM, et al. Tirzepatide once weekly for obesity (SURMOUNT-1). NEJM, 2022.
- Aronne LJ, et al. Tirzepatide vs semaglutide for obesity (SURMOUNT-5). NEJM, 2025.
- Aronne LJ, et al. Continued tirzepatide for weight maintenance (SURMOUNT-4). JAMA, 2024.
- FDA. Concerns with unapproved GLP-1 drugs used for weight loss.
- Source summary: PeptideDosages.com research overview (rewritten for NVO).
Laboratory research material: GLP-2T (NVO research code) Research Use Only