Tirzepatide (Zepbound, Mounjaro)
Tirzepatide is the medication behind Zepbound and Mounjaro. It is FDA-approved, given as a weekly injection, and produced some of the largest average weight loss seen in trials.
- Legal lane: FDA-approved, prescription only
- Evidence grade: A
- Form: weekly injection under the skin
- Brands: Zepbound (weight, sleep apnea), Mounjaro (type 2 diabetes)
- Self-pay cost: from $299 a month
What it is
Tirzepatide acts on two gut-hormone receptors, GIP and GLP-1. Like semaglutide, it reduces appetite and slows stomach emptying.
What the evidence shows
In its main weight-loss trial, adults on the highest dose, 15 mg a week, lost an average of 20.9% of their body weight over 72 weeks. Results vary, and weight tends to return when treatment stops.
Dosing on the FDA label
This schedule comes from the Zepbound prescribing information.
| Stage | Dose, once a week | Notes |
|---|---|---|
| Weeks 1 to 4 | 2.5 mg | For starting treatment only. Not approved as a maintenance dose. |
| From week 5 | 5 mg | First maintenance-level dose. |
| Further steps | 7.5 mg, 10 mg, 12.5 mg, 15 mg | Increases of 2.5 mg, each after at least four weeks on the current dose. |
| Maintenance | 5 mg, 10 mg or 15 mg | For sleep apnea: 10 mg or 15 mg. Maximum is 15 mg. |
The prescriber chooses the maintenance dose based on response and how well each step is tolerated. If a dose is missed, the label says to take it as soon as possible within four days.
Side effects and warnings
- The most common side effects are in the gut, including nausea, diarrhea, vomiting and constipation.
- The label carries a boxed warning about thyroid C-cell tumors, seen in rat studies. It should not be used by people with a personal or family history of medullary thyroid cancer or MEN 2.
- The full label lists other serious risks. Read the Medication Guide and raise your history with the prescriber.
What it costs without insurance
| Zepbound dose | Manufacturer self-pay price, per month |
|---|---|
| 2.5 mg | $299 |
| 5 mg | $399 |
| 7.5 mg to 15 mg | $449 |
Prices were checked in October 2026 and change often. They apply to vials and pens bought through the manufacturer's self-pay program.
Compounded tirzepatide
Compounded tirzepatide is not FDA-approved. Since the shortage ended in December 2024, compounding is allowed only in narrow, patient-specific cases. The FDA had received more than 730 adverse event reports linked to compounded tirzepatide as of May 31, 2026.
Sources
- Zepbound prescribing information (Eli Lilly)
- Zepbound label, DailyMed
- Trial results summary
- GoodRx: Zepbound dosage and self-pay prices
- Compounded GLP-1 rules and adverse event counts
Choosing between the two approved options? See semaglutide vs tirzepatide.