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 (30 mg Vial) Dosage Protocol
- Vial
- 30 mg Tirzepatide
- Add diluent
- 3 mL
- Concentration
- 10 mg/mL
- 1 unit (U-100)
- 100 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 | 25 units | 0.25 mL |
| Weeks 5 to 8 | 5 mg | 50 units | 0.5 mL |
| Weeks 9 to 12 | 7.5 mg | 75 units | 0.75 mL |
| Weeks 13 to 16 | 10 mg | 100 units | 1 mL |
| Weeks 17 to 20 | 12.5 mg | 125 units | 1.25 mL |
| Weeks 21+ | 15 mg | 150 units | 1.5 mL |
How to mix
- Clean the vial stopper and gather the sterile supplies required by the research procedure.
- Add 3 mL of the documented sterile diluent slowly down the vial wall.
- Gently swirl or roll until dissolved. Do not shake.
- Label the vial 10 mg/mL with the preparation date and follow the exact product storage and discard instructions.
Dosing details
- The weekly dose schedule below reflects population-level labeling and trial designs, not an individualized treatment recommendation.
- Weeks 1–4: The labeled starting dose is used once weekly during the initiation stage.
- Weeks 5–8: The next labeled weekly step follows that initiation period.
- Later steps: Further increases occur in 2.5 mg increments every 4 weeks when escalation is selected.
- Why escalation is gradual: The Zepbound label states that the schedule is used to reduce gastrointestinal adverse reactions, and trials reported that gastrointestinal events occurred most often during escalation.
- Measurement: The primary chart keeps each weekly mass, U-100 marking, and mL volume together. Rows above 100 U-100 units exceed one 1 mL syringe at this calculated concentration.
- The tirzepatide dose schedule is deliberately staged. Current U.S. labeling begins with four weeks at 2.5 mg, then moves to 5 mg, with any later increase occurring only after at least four weeks at the current dose. Each stage therefore normally includes 4 weekly doses before the label permits clinicians to increase the dose; higher doses are not triggered by vial size.
- Initiation is distinct from maintenance: The Zepbound label identifies the first stage as an initiation dose, not an approved maintenance dose.
- Escalation is tolerability-led: The label uses gradual escalation to reduce the risk of gastrointestinal adverse reactions, while pivotal trials reported that nausea, diarrhea, vomiting, and constipation were concentrated during dose increases.
- Response and tolerability matter: The weight-management label directs selection of a maintenance dose according to treatment response and tolerability.
- Vial size does not change the schedule: A 30 mg label describes total nominal vial content. It does not create a 30 mg weekly dose or change the labeled escalation increments.
Storage
- Storage depends on the exact formulation and presentation; the research-vial calculation on this page must not be substituted for a manufacturer’s storage instructions.
- Before preparation: Keep the vial dry, protected from light, and stored according to the exact supplier documentation.
- After preparation: Refrigerate only when permitted by the exact formulation and diluent instructions.
- Labeling: Record the 10 mg/mL concentration, preparation date, storage conditions, and documented discard date.
- Approved presentations: FDA-approved tirzepatide products have presentation-specific storage and handling instructions that should be read directly in their current prescribing information.
- Handling: Avoid unnecessary agitation and do not infer a universal beyond-use date from vial strength alone.
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