Metabolic & weight

Tirzepatide

Also called Zepbound, Mounjaro, LY3298176

Tirzepatide is a weekly shot that acts on two gut-hormone receptors, GIP and GLP-1, at once. It is approved for type 2 diabetes, weight management, and sleep apnea linked to obesity. In trials it produced about 15–21% average weight loss.

FDA-approvedApproved by the FDA for at least one use after large human trials.

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Overview

How it works

Established: tirzepatide activates both the GIP and GLP-1 receptors. Together these raise glucose-dependent insulin release, lower glucagon, slow stomach emptying, and reduce appetite and food intake. How much the GIP component adds to weight loss beyond GLP-1 action is still being studied.

What research shows

SURMOUNT-1 (label Study 1; human RCT in adults with obesity without diabetes, 72 weeks): mean weight change −15.0% (5 mg), −19.5% (10 mg), −20.9% (15 mg) vs −3.1% with placebo; 56.7% on 15 mg lost at least 20% of body weight.
Label Study 2 (human RCT in adults with type 2 diabetes): −12.8% (10 mg) and −14.7% (15 mg) vs −3.2% with placebo.
Approved for obstructive sleep apnea in adults with obesity based on placebo-controlled trials (label).

Doses studied in people

Study or label	Dose used	Source
FDA label, Zepbound: start and escalation	2.5 mg once weekly for 4 weeks (starter dose only), then 5 mg; increase in 2.5 mg steps after at least 4 weeks on each dose, subcutaneous	¹
FDA label, Zepbound: maintenance	5, 10, or 15 mg once weekly for weight management; 10 or 15 mg for sleep apnea; maximum 15 mg weekly	¹
SURMOUNT-1 RCT, adults with obesity (label Study 1)	5, 10, or 15 mg once weekly, subcutaneous, 72 weeks	¹

Doses are from the FDA Zepbound label; the Mounjaro (diabetes) label uses the same 2.5–15 mg weekly range.

Read this first: these are the amounts given to participants in published studies or written on official prescribing labels, reported for reference. They are not recommendations. Trial doses were chosen for specific patients under medical supervision, and a dose that is safe in one person can be harmful in another.

Weekly protocol

How the schedule looks week by week. Each chart says where it comes from: a prescribing label, a clinical trial, or a protocol commonly reported online.

Zepbound label titration

Prescribing label

One week

D1D2D3D4D5D6D7

Once weekly · Subcutaneous injection

Dose by week

2.5 mgStarting · wk 1–4

5 mgwk 5–8

7.5 mgwk 9–12

10 mgwk 13–16

12.5 mgwk 17–20

15 mgMaintenance · wk 21+

Course: Ongoing (maintenance)
Note: 2.5 mg is a starter dose only; increase in 2.5 mg steps after at least 4 weeks on each dose. Maintenance is 5, 10 or 15 mg for weight reduction (10 or 15 mg for sleep apnea); maximum 15 mg weekly.
Source: ZEPBOUND prescribing information (FDA, revised 04/2026)

Reference only, not a recommendation. Label and trial schedules were set for specific patients under medical supervision. Use the calculator only to understand the arithmetic.

Safety

Boxed warning (label): thyroid C-cell tumors in rats; human relevance unknown. Contraindicated with personal or family history of medullary thyroid carcinoma or MEN 2.
Most common side effects (label, ≥5%): nausea, diarrhea, vomiting, constipation, abdominal pain, indigestion, injection site reactions, fatigue, allergic reactions, burping, hair loss, and reflux.
Label warnings include severe GI reactions, kidney injury from dehydration, gallbladder disease, pancreatitis, anaphylaxis and angioedema, low blood sugar with insulin or sulfonylureas, diabetic retinopathy complications, and aspiration under anesthesia.
May reduce effectiveness of oral birth control during dose starts and increases (label).

Report side effects of any drug or product to the FDA through MedWatch. For a possible poisoning in the US, call Poison Control at 1-800-222-1222.

Legal status

FDA: FDA-approved as Mounjaro (type 2 diabetes, 2022) and Zepbound (chronic weight management, 2023; obstructive sleep apnea in adults with obesity). Label revised 04/2026.
Compounding: FDA declared the tirzepatide shortage resolved in December 2024. Enforcement discretion ended Feb 18, 2025 (503A) and Mar 19, 2025 (503B); a court backed FDA's decision. Compounding of copies is no longer permitted except for documented patient-specific clinical differences. FDA sent 30 warning letters to telehealth sellers of compounded GLP-1s on Mar 3, 2026.
Sports (WADA): Not prohibited. Tirzepatide markers are tracked under WADA's Monitoring Program from Jan 1, 2026 (per NADA); status unchanged for the 2027 list.
Other: Not a controlled substance. Approved in the EU as Mounjaro.

Rules change often. See Legal status of peptides for how these categories work.

Storage and stability

Per label: refrigerate pens/vials; may be kept unrefrigerated for a limited period as described in the label.

General lab handling, not instructions for personal use. See Storage and stability.

History

Developed by Eli Lilly. Approved as Mounjaro for type 2 diabetes (2022) and as Zepbound for chronic weight management (2023). Zepbound added an indication for moderate-to-severe obstructive sleep apnea in adults with obesity. Label last revised 04/2026.

Common questions

Is tirzepatide FDA-approved?

Yes. It is approved as Mounjaro for type 2 diabetes (2022) and as Zepbound for weight management (2023) ¹. Zepbound is also approved for moderate-to-severe obstructive sleep apnea in adults with obesity ¹.

What does the research show?

In SURMOUNT-1, adults with obesity lost an average of 15.0% to 20.9% of body weight over 72 weeks depending on dose, vs 3.1% on placebo ¹⁷. In adults with type 2 diabetes, weight loss was 12.8% to 14.7% vs 3.2% on placebo ¹.

What doses are on the label?

The Zepbound label starts at 2.5 mg weekly for 4 weeks, then raises the dose in 2.5 mg steps to a 5, 10 or 15 mg weekly maintenance dose, with 15 mg the maximum ¹. Mounjaro uses the same range; these are label figures, not personal guidance ¹.

What are the side effects?

Common side effects include nausea, diarrhea, vomiting, constipation and injection site reactions ¹. The label has a boxed warning about thyroid tumors in rats and notes it may make birth control pills less effective when starting or raising the dose ¹.

Are compounded versions still allowed?

FDA declared the shortage resolved in December 2024, and the grace periods for compounders ended in February and March 2025 ². A court backed FDA's decision, and copies are now allowed only for documented patient-specific medical differences ³.

Is tirzepatide banned in sport?

No. It is not prohibited, but WADA tracks it in its Monitoring Program, and its status is unchanged for the 2027 list ⁵⁶.

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Sources

Last reviewed 2026-10-25 · How we research · Found an error? See our corrections policy.