Skip to main content

Page last checked

FDA-approved medicine

Tirzepatide Zepbound · Mounjaro

Tirzepatide is the drug in Zepbound and Mounjaro. It works on two gut hormone signals involved in appetite and blood sugar.

What matters first

Why people look it up
People take Zepbound for long-term weight management and Mounjaro for type 2 diabetes.
What the evidence shows
Both products have FDA approval and use weekly injections. Their labels cover different uses, so the product name matters.
Dose status
With tirzepatide, you start at 2.5 mg once a week for the first 4 weeks. That opening step is not the working dose — it is there to let your body get used to the drug before the label steps it up toward 5–15 mg.

Evidence snapshot

FDA-approved label

The fastest way to see what kind of evidence this page is built on.

Regulation
FDA approvedZepbound · Mounjaro
Dose source
FDA label schedule6 labeled steps
Safety evidence
15 listed safety findingsIncludes a boxed warning
Sources
3 cited sourcesMedical review complete · 2026-07-22
Open the shareable evidence image
Tirzepatide at a glance: FDA-approved label, dosing basis, regulatory status, safety coverage, and cited-source count. These details summarize the available sources; they are not treatment recommendations.

Further down: research and dosing details · how it works · how good the evidence is · questions

Medically reviewed by Jennifer Montecillo, MD · non-practicing medical reviewerReviewed 2026-07-22open the primary sources

What is known about Tirzepatide

Tirzepatide is the drug in Zepbound and Mounjaro. Zepbound is FDA-approved for long-term weight management, and Mounjaro for type 2 diabetes. Both are taken once a week. The label starts at 2.5 mg and raises the dose no faster than every 4 weeks.

Tirzepatide research and regulatory details: evidence quality, approval status, doses, handling, and presentation.
TopicValue
Strongest sourceFDA label
FDA approvalApproved (Zepbound, Mounjaro)
Starting dose2.5 mg once weekly for 4 weeks — from the FDA-approved label
Maintenance dosing5–15 mg once weekly (5, 10, or 15 mg) — from the FDA-approved label
Half-life≈ 5 days
After mixing a multi-dose vial28 days · USP <797> multi-dose vial. General pharmacy standard — check the pharmacy label for the vial you have.
Typical vials5 mg · 10 mg · 15 mg · 30 mg · 60 mg

Every row links back to a source listed below. These facts are for reference, not a personal recommendation.

How Tirzepatide works

Tirzepatide acts at GIP + GLP-1. Here is what that means.

A dual agonist switches on the receptors for both hormones your gut releases after eating: GLP-1 and GIP (glucose-dependent insulinotropic polypeptide). Both were first understood as insulin boosters, and combining them started out as a diabetes idea. The weight loss that followed was bigger than the GLP-1 half alone would explain, and researchers still do not agree on why.

◆ Receptor targets2 of 4 · GIP + GLP-1
4What each receptor does — 4 rows in the data table
Receptors targeted by Tirzepatide, and what each receptor does
ReceptorTirzepatideWhat it does
GLP-1targetedInsulin release while blood sugar is rising, less glucagon, slower stomach emptying, and less appetite — the same physiology a single-target drug produces, carried here by the same molecule.
GIPtargetedpancreatic isletGIP is the other gut hormone, released higher up the small intestine. It boosts insulin alongside GLP-1, which is why the two together move blood sugar more than either does alone.adipose tissue and brainGIP receptors also sit on fat cells, where the hormone has a hand in how nutrients get stored and how blood moves through fat tissue, and in the brain regions handling appetite and nausea. What GIP actually contributes to weight loss is disputed — blocking the same receptor has also produced benefit in experiments.
Glucagonnot targeted—
Amylinnot targeted—

The same four receptor groups are shown for every drug, so the differences are easy to compare. Targets come from the drug class. Any result specific to Tirzepatide comes from the cited sources.

The honest summary: the two-receptor design has beaten single-target GLP-1 in trials, and the explanation is unfinished. One leading idea is that GIP signaling in the brain dampens the nausea that limits GLP-1 dosing, so a dual agonist can be pushed further before side effects stop it. That is a hypothesis, not a finding — any confident story about what GIP does is running ahead of the evidence.

What repeated weekly dosing accumulates to

A new dose can arrive before the prior one has cleared. The amount then rises toward a steady pattern over several doses. The curve uses one cited figure: the 5 days half-life. It is arithmetic, not a measurement of anyone’s blood.

◆ How repeated doses build uplong-term peak ≈ 1.61× one dose

Estimated amount compared with one dose, taken once weekly. Based on the cited half-life, not on blood test results.

8Exact values — 8 rows in the data table
Tirzepatide — exposure after each once weekly dose, as a multiple of a single dose, computed from the cited half-life
WeekJust after that doseJust before the next doseToward long-term level
11.00×0.38×62%
21.38×0.52×86%
31.52×0.58×95%
41.58×0.60×98%
51.60×0.61×99%
61.61×0.61×100%
71.61×0.61×100%
long-term level1.61×0.61×100%

This is a math estimate based on the cited half-life of 5 days. Each dose is added to what has not yet left the body, so the curve rises toward 1.61× one dose — within 5% of that level by week 3. This is not a measured blood level and does not predict one person’s result. Source of the half-life: Tirzepatide prescribing information — DailyMed (NIH) · retrieved 2026-07-22.

What the evidence for Tirzepatide is

The dosing numbers come from an FDA-approved prescribing label. FDA reviewed the manufacturer’s studies before approving the product, and the label can change when new dosing or safety information appears.

FDA label
What it establishes
The schedule was tested for the approved use, FDA reviewed the results, and the approved product must meet manufacturing standards.
What it does not establish
It does not show that every dose step is right for every person. A clinician still has to consider health history, side effects and other medicines.

Use these numbers for the named product and approved use. A different brand, product form or use may have a different schedule.

Where Tirzepatide is in clinical trials

200 registered studies; the program has reached phase 4, and 69 are still enrolling.

The soonest a running study expects to finish measuring people is August 2026. That is when the sponsor expects to finish collecting the main measurement. It is not a results date, and not a date anything goes on sale.

  • Phase 4Recruiting

    Efficacy, Safety, and Tolerability of Tirzepatide in Real-World Conditions in Paraguay.

    Las Rías Medical Center · Obesity, Diabetes Mellitus, Type 2 · 160 participants planned · started July 2026

    Main measurement due August 2027 (sponsor estimate)

    NCT07588438 on ClinicalTrials.gov

  • Phase 4Recruiting

    Tirzepatide's Role in Postmenopausal HR+ Breast Cancer Survivors

    Weill Medical College of Cornell University · Obesity (Disorder), Breast Cancer · 30 participants planned · started June 2026

    Main measurement due December 2027 (sponsor estimate)

    NCT07257484 on ClinicalTrials.gov

  • Phase 4Recruiting

    The Effect of Tirzepatide on Menopausal Vasomotor Symptoms and Biological Aging in Post-menopausal Women With Obesity

    Mayo Clinic · Obesity, Menopause Hot Flashes · 40 participants planned · started April 2026

    Main measurement due September 2027 (sponsor estimate)

    NCT07218445 on ClinicalTrials.gov

We left one registration out of the count above. Registering a study does not prove it is running, and these did not hold up.

  • NCT07481747 — template batch: 7 of 8 studies from “Hudson Biotech” claim the same primary completion date 2027-02-14, all at Peking University Shenzhen Hospital; NCT07481734 declares itself an example

Check them yourself and disagree with us if you think we got it wrong.

A registered study means a sponsor filed a plan and started enrolling. It is not evidence the drug works, and most drugs tested in people never reach a pharmacy. Sponsors write and update these sources themselves; the National Library of Medicine publishes them without checking them.

ClinicalTrials.gov · retrieved 2026-08-23

Every compound we track, and what stage each one has reached →

Regulatory status

FDA-approved as branded pens.

Compounded tirzepatide now faces tight limits. FDA declared the shortage over in late 2024. It has proposed dropping tirzepatide from the 503B bulks list.

That leaves one narrow lane: 503A compounding for a named patient with a documented clinical need.

Tirzepatide is not on FDA’s shortage list, checked 14 August 2026. That matters here because shortage listing is what allowed compounded copies, and it is the one part of this page that can change any day.

Full regulatory tracker →

How Tirzepatide compares

Each page says which kind of comparison it is: one trial that tested both, or two separate trials read side by side — which is much weaker, however close the numbers look.

Where tirzepatide stands in retatrutide vs tirzepatide

Dosing, source strength, half-life and reactions for retatrutide vs tirzepatide, cited row by row past tirzepatide.

The tirzepatide half of tirzepatide vs semaglutide

Each page in tirzepatide vs semaglutide on its own terms, rather than folded into tirzepatide.

Wegovy vs zepbound, from the tirzepatide side

SURMOUNT-5 studied 751 adults for 72 weeks. This sits beyond tirzepatide.

Survodutide vs tirzepatide, with the tirzepatide page in full

What each molecule engages, and what that changes, apart from tirzepatide.

Where to go next on Tirzepatide

The schedule, the side effects and the mixing math each have their own page.

Tirzepatide side effects, as the sources describe them

When tirzepatide reactions tend to appear, tied to that compound’s own escalation steps.

What the tirzepatide label specifies at each step

See how the tirzepatide label increases the dose and which amounts are used for maintenance.

Doses per 5 mg tirzepatide vial, on the calculator

The nearest syringe line to the target, and the rounding error it introduces for tirzepatide.

Mixing a 10 mg tirzepatide vial, water volume by water volume

What each bacteriostatic-water volume does to a 10 mg tirzepatide vial, in mg/mL and units.

Mixing a 5 mg tirzepatide vial, water volume by water volume

What each bacteriostatic-water volume does to a 5 mg tirzepatide vial, in mg/mL and units.

Mounjaro as a product, not only tirzepatide as a molecule

The Mounjaro label starts at 2.5 mg and tops out at 15 mg, apart from tirzepatide.

Reading the tirzepatide Instructions for Use

Route, frequency and site rotation as the tirzepatide document sets them out.

Check the same draw on a vial that is not tirzepatide

Any vial at all, tirzepatide among them, with the arithmetic shown rather than hidden.

Zepbound as a product, not only tirzepatide as a molecule

The Zepbound label starts at 2.5 mg and tops out at 15 mg, apart from tirzepatide.

Compounded tirzepatide against the approved product

FDA cites more than 730 side-effect reports involving compounded tirzepatide.

Safety notes

  • Prescription medicine — dosing decisions belong to the prescribing clinician
  • Escalate no faster than every 4 weeks, and only if the current dose is tolerated
  • Missed dose: take within 4 days (96 h), otherwise skip; keep doses ≥ 72 h apart

Questions about Tirzepatide

Is Tirzepatide FDA-approved?

Yes — it is sold as Zepbound and Mounjaro. That is why the schedule on this site is quoted from a label rather than summarized from a study.

How is Tirzepatide taken?

By injection under the skin, once a week. The dosing page has every step, with the source on each row.

How does Tirzepatide differ from the other compounds in this class?

It acts at GIP + GLP-1. The nearest alternatives act elsewhere: Semaglutide (GLP-1 alone), Liraglutide (GLP-1 alone), Retatrutide (GIP + GLP-1 + glucagon), Cagrilintide (amylin), Survodutide (glucagon + GLP-1), Mazdutide (glucagon + GLP-1), Zenagamtide (GLP-1 + amylin), Pemvidutide (glucagon + GLP-1). Adding or removing a receptor changes both the effect and how much of it people can tolerate, so these molecules are not swappable at the same number of milligrams. Comparing them milligram for milligram is the most common mistake in this category.

What is not known about Tirzepatide?

It does not show that every dose step is right for every person. A clinician still has to consider health history, side effects and other medicines.

Is there a Tirzepatide dosing schedule on this site?

Yes — the label schedule is published in full, one row per step, each row carrying its source. Open the Tirzepatide dosage chart.

Questions readers ask

How long does it take to lose 20 lbs on tirzepatide?

No trial published a time to a pound target, so nobody can answer this honestly with a date. What was measured is different: in SURMOUNT-5, 751 adults took tirzepatide for 72 weeks and lost 20.2% of their body weight on average.

That is an average across hundreds of people over about 17 months, not a schedule one person can hold themselves to. It also sits at the top of the label ladder rather than the start. The first four weeks are the 2.5 mg dose, which the label says is not one to stay on.

What are the drawbacks of tirzepatide?

Three stand out on the label. It carries a boxed warning. The stomach and bowel effects are common rather than rare, and it is a weekly injection rather than a pill.

The boxed warning is about thyroid C-cell tumors in rodents. Whether it does the same in people is unknown. The label rules it out for a personal or family history of medullary thyroid cancer, or of MEN 2.

Is tirzepatide the same as Ozempic?

No. Ozempic is semaglutide, which engages one receptor family; tirzepatide engages two, GIP as well as GLP-1.

They are also different products from different companies with different dose ladders. The tirzepatide brands are Zepbound and Mounjaro.

Who cannot take tirzepatide?

The label names one group outright: anyone with a personal or family history of medullary thyroid cancer, or of MEN 2. That comes from the boxed warning.

Beyond that the label does not publish a list of people who cannot take it. It flags situations that need watching instead. Those include pancreatitis, gallbladder disease, kidney injury after fluid loss, and low blood sugar alongside insulin.

3primary sources, each with the day we read it — open the documents used on this page