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GIP and GLP-1 receptor agonist

Tirzepatide

Tirzepatide is a once-weekly GIP and GLP-1 receptor agonist injection, sold as Mounjaro and Zepbound.

Medical review in progressLast reviewed

US regulatory status

FDA-approved prescription drug

Eli Lilly makes both FDA-approved products: Mounjaro, for type 2 diabetes (adults and children 10 and older) and to lower heart risk in high-risk adults with type 2 diabetes, and Zepbound, for long-term weight management and for sleep apnea with obesity in adults. Compounded tirzepatide is not FDA-approved: the FDA declared the shortage resolved on December 19, 2024, and in April 2026 proposed excluding it from the list outsourcing facilities may compound from. The FDA has also warned sellers of “research use only” tirzepatide.

As of

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On this page
  1. US regulatory status
  2. At a glance
  3. What the research shows
  4. Side effects and safety
  5. Vial math
  6. Questions people ask
  7. Sources
  8. Related compounds

At a glance

Also known as
Mounjaro, Zepbound, LY3298176
Supplied as
Several forms, depending on the product
Research
Strong human evidence
US status
US status: FDA-approvedchecked

What the research shows

Evidence grade

Strong human evidence

Consistent results from large randomized controlled trials in people.

In SURMOUNT-1 (2,539 adults with obesity or overweight but no diabetes, 72 weeks), average weight change was −15.0% to −20.9% across the doses tested, compared with −3.1% on placebo. In SURMOUNT-5, an open-label head-to-head trial in 751 adults with obesity but no diabetes, weight change at 72 weeks was −20.2% with tirzepatide and −13.7% with semaglutide. In type 2 diabetes, SURPASS-2 (1,879 adults, 40 weeks) found HbA1c fell by 2.01 to 2.30 percentage points with tirzepatide and 1.86 with semaglutide. SURPASS-CVOT followed 13,299 adults with type 2 diabetes and heart disease for a median of about 4 years: in the published trial, heart attack, stroke or cardiovascular death occurred in 12.2% on tirzepatide and 13.1% on dulaglutide (hazard ratio 0.92), so tirzepatide was noninferior but not shown to be superior. In SURMOUNT-OSA, two 52-week trials in 469 adults with obesity and moderate to severe sleep apnea, breathing events during sleep fell by 25.3 and 29.3 per hour on tirzepatide, compared with 5.3 and 5.5 per hour on placebo. In SUMMIT (731 adults with obesity and heart failure with preserved ejection fraction), cardiovascular death or worsening heart failure occurred in 9.9% on tirzepatide and 15.3% on placebo; this is not an approved use. Eli Lilly funded all of these trials.

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How we grade evidence

  1. Strong human evidence · this page

    Consistent results from large randomized controlled trials in people.

  2. Limited human evidence

    Some studies in people, but they are small, short, early-phase or uncontrolled.

  3. Mixed evidence

    Studies in people disagree, or strong evidence for one use sits beside weak evidence for another.

  4. Animal or lab studies only

    Studied in cells or animals, not properly in people. Animal results may not apply to humans.

The grade describes how much research exists and in whom. It is not a judgment that a compound works or is safe.

Side effects and safety

The most common side effects are digestive: nausea, diarrhea, vomiting, constipation, stomach pain, indigestion and decreased appetite, mostly while the dose is being increased. In the Zepbound weight trials, nausea affected 25% to 29% of people (8% on placebo) and hair loss 4% to 5% (1% on placebo), more often in women. Both labels carry a boxed warning: tirzepatide caused thyroid C-cell tumors in rats, it is unknown whether it does in people, and it must not be used by anyone with a personal or family history of medullary thyroid carcinoma, or by anyone with MEN 2. Other label warnings include pancreatitis (including fatal cases), gallbladder disease, severe stomach and bowel side effects, kidney injury from dehydration, serious allergic reactions, diabetic eye complications and aspiration during anesthesia or deep sedation. Low blood sugar is more likely with insulin or a sulfonylurea, so the prescriber may lower those doses. Birth control pills may work less well for 4 weeks after starting and after each dose increase. The FDA had received more than 730 adverse event reports for compounded tirzepatide as of May 31, 2026.

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Vial math

Pre-filled calculators turn your vial, water and prescribed dose into syringe units.

From the FDA label

The schedule printed on the Mounjaro and Zepbound labels, in syringe units for your vial. Follow your prescriber.

Pre-filled for your vial size

Branded pens and vials are ready to use and need no mixing. These pages are for vials mixed from powder.

This is arithmetic, not medical advice. Confirm with your prescriber or pharmacist.

Questions people ask

Is tirzepatide the same as Mounjaro?

Yes. Tirzepatide is the active ingredient in Mounjaro, and also in Zepbound. Both are Eli Lilly products with the same once-weekly strengths; they differ in approved use. Mounjaro is for type 2 diabetes and lowering heart risk in some adults with diabetes. Zepbound is for weight management and sleep apnea with obesity. Compounded tirzepatide is not the same: it is not FDA-approved, and the FDA has not checked its quality.

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What are the side effects of Mounjaro?

On the Mounjaro label, the most common are nausea (12% to 18% of people, vs 4% on placebo), diarrhea, decreased appetite, vomiting, constipation, indigestion and stomach pain. They are most frequent while the dose is being increased. Zepbound’s label adds injection-site reactions, tiredness, belching, heartburn and hair loss. Stop and call your prescriber for severe stomach pain that won’t go away, which can spread to your back: it can be pancreatitis.

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Does tirzepatide cause cancer?

It is not known. Tirzepatide caused thyroid C-cell tumors in rats, which is why both labels carry a boxed warning, but it is unknown whether it causes thyroid tumors, including medullary thyroid carcinoma, in people. It must not be used if you or a family member had medullary thyroid carcinoma, or if you have MEN 2. Tell your prescriber about a lump or swelling in your neck, hoarseness, trouble swallowing or shortness of breath.

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Is compounded tirzepatide FDA-approved?

No. The FDA does not review compounded drugs for safety, effectiveness or quality. Since the shortage ended in December 2024, pharmacies may compound tirzepatide only under narrow rules, and the FDA has warned about dosing concerns and fraudulent labels. If you use a vial, the tirzepatide dosing chart in units converts the dose your prescriber gave you into syringe units for your vial’s concentration.

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What is the half-life of tirzepatide?

About 5 days, according to the Mounjaro label, and about 5 to 6 days in people with overweight, obesity or sleep apnea, according to the Zepbound label. With once-weekly injections, blood levels reach a steady state after about 4 weeks.

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What are the long-term side effects of tirzepatide?

They are known only as far as the trials go: 72 weeks in the main weight trials, and a median of about 4 years in SURPASS-CVOT, where adverse events were similar to dulaglutide overall, with more digestive side effects. Beyond that, effects are unknown. The label warnings that matter over time are gallbladder problems, pancreatitis and thyroid C-cell tumors, which tirzepatide caused in rats (the risk in people is unknown). Tell your prescriber about any new or lasting symptoms.

Sources

Sources

  1. MOUNJARO (tirzepatide) injection, prescribing informationDailyMed, U.S. National Library of Medicine, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  2. ZEPBOUND (tirzepatide) injection, prescribing informationDailyMed, U.S. National Library of Medicine, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  3. FDA clarifies policies for compounders as national GLP-1 supply begins to stabilizeU.S. Food and Drug Administration, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  4. FDA Proposes to Exclude Semaglutide, Tirzepatide, and Liraglutide on 503B Bulks ListU.S. Food and Drug Administration, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  5. FDA’s Concerns with Unapproved GLP-1 Drugs Used for Weight LossU.S. Food and Drug Administration, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  6. Warning letter: TXP Innovations LLC dba Tex Peptides (MARCS-CMS 735067)U.S. Food and Drug Administration, 2026 · Accessed Oct 16, 2026 (opens in a new tab)
  7. Tirzepatide Once Weekly for the Treatment of ObesityN Engl J Med, 2022 · Accessed Oct 16, 2026 (opens in a new tab)
  8. Tirzepatide as Compared with Semaglutide for the Treatment of ObesityN Engl J Med, 2025 · Accessed Oct 16, 2026 (opens in a new tab)
  9. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 DiabetesN Engl J Med, 2021 · Accessed Oct 16, 2026 (opens in a new tab)
  10. Cardiovascular Outcomes with Tirzepatide versus Dulaglutide in Type 2 DiabetesN Engl J Med, 2025 · Accessed Oct 16, 2026 (opens in a new tab)
  11. Tirzepatide for the Treatment of Obstructive Sleep Apnea and ObesityN Engl J Med, 2024 · Accessed Oct 16, 2026 (opens in a new tab)
  12. Tirzepatide for Heart Failure with Preserved Ejection Fraction and ObesityN Engl J Med, 2025 · Accessed Oct 16, 2026 (opens in a new tab)

Related compounds

Guides

Medical review in progressLast reviewed

Every medical and regulatory statement on this page links to a checkable source, listed above. Peptinote does arithmetic and education, not medical advice, and never sells or links to sellers of peptides.

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