Tirzepatide: Uses, Side Effects, and What’s Actually FDA-Approved

Tirzepatide is a synthetic peptide that switches on two different gut-hormone receptors at the same time — the GIP receptor and the GLP-1 receptor — which is why it tends to lower blood sugar and appetite more than medications that work on just one. It is FDA-approved and sold in the U.S. by Eli Lilly and Company under two brand names: Mounjaro for type 2 diabetes, and Zepbound for chronic weight management and for obstructive sleep apnea. Compounded tirzepatide is a separate question with a separate answer, and that answer changed during 2025.

Tirzepatide is FDA-approved and marketed under two brand names: Mounjaro, approved May 13, 2022 for type 2 diabetes (NDA 215866), and Zepbound, approved November 8, 2023 for chronic weight management and December 20, 2024 for moderate-to-severe obstructive sleep apnea in adults with obesity (NDA 217806). Compounded tirzepatide is a different matter: FDA determined the tirzepatide shortage resolved on December 19, 2024, and the period of enforcement discretion for compounders ended February 18, 2025 for state-licensed pharmacies and March 19, 2025 for outsourcing facilities, as of September 2026.

If you got here because a friend, a podcast, or a telehealth ad mentioned tirzepatide, the useful orientation is this: It belongs to the same broad family as [GLP-1 peptides for weight loss], it is a peptide in the literal chemical sense (more on that below, and here’s the plain-language guide to [what peptides are]), and it is the more-than-one-receptor cousin of [semaglutide], which acts on the GLP-1 receptor alone.

What tirzepatide is

Tirzepatide is a lab-made, 39-amino-acid peptide designed to mimic two hormones your gut releases after you eat. It is a prescription drug, not a supplement, and every legitimate U.S. version of it is dispensed under one of two brand names.

Is tirzepatide a peptide?

Yes. Tirzepatide is a peptide — a chain of amino acids — engineered to resemble the naturally occurring hormone GIP closely enough to activate its receptor, with modifications that let it also activate the GLP-1 receptor and stay in the body far longer than the natural hormones do.

That’s worth saying plainly, because “peptide” in wellness marketing has come to imply something unregulated and vaguely natural. Tirzepatide is the opposite case: a peptide that went through full FDA drug review, twice.

Is tirzepatide a GLP-1?

Partly. Tirzepatide is a GLP-1 receptor agonist, but it is also a GIP receptor agonist — a dual agonist. Drugs described simply as “GLP-1s” (semaglutide among them) hit one receptor; tirzepatide hits two.

Is tirzepatide FDA-approved?

Yes — under two separate new drug applications, for three indications total. The full breakdown is in the table below.

How tirzepatide works: the dual GIP/GLP-1 mechanism

Tirzepatide activates both the GIP receptor and the GLP-1 receptor, the two incretin pathways your body uses to coordinate insulin release, blood sugar, and appetite after a meal. According to NCBI StatPearls’ tirzepatide entry, this dual receptor agonism “decreases hyperglycemia significantly more than GLP-1 agonist agents and reduces the patient’s appetite.”

In practical terms, that means three things happening at once: your pancreas releases insulin more responsively when blood sugar rises, your stomach empties more slowly, and the signals that tell your brain you’ve eaten enough get louder and last longer. The slowed stomach emptying is also the reason most of the common side effects are digestive.

The GIP half is the newer idea. GLP-1 as a drug target has been well-studied for years; adding GIP activation on top of it is what distinguishes tirzepatide from the single-target drugs, and it is the leading explanation for why it outperforms them on blood sugar and body weight in head-to-head testing.

We do not cover dosing, titration schedules, or injection instructions anywhere on this page. Those belong to you and your prescriber.

What tirzepatide is actually FDA-approved for

Three indications, two applications, two brand names — all as of September 2026.

Sources, in order: the FDA Mounjaro approval letter, the FDA Zepbound approval letter, and the FDA Zepbound obstructive sleep apnea supplement letter.

Spelled out per indication, in the FDA’s own framing:

• Mounjaro is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus (NDA 215866, approved May 13, 2022).
• Zepbound is indicated as an adjunct to a reduced-calorie diet and increased physical activity for chronic weight management in adults with a BMI of 30 or greater, or 27 or greater with at least one weight-related comorbid condition (NDA 217806, approved November 8, 2023).
• Zepbound is additionally approved to treat moderate to severe obstructive sleep apnea in adults with obesity (NDA 217806 S-013, approved December 20, 2024).

The Zepbound record is publicly viewable in Drugs@FDA under NDA 217806, which lists ZEPBOUND (tirzepatide), Eli Lilly and Company, original approval 11/08/2023, granted priority review. FDA also published a plain-language press announcement the day the weight-management approval came through.

Mounjaro vs. Zepbound: what’s the difference?

Same molecule, different approved indication. Zepbound is tirzepatide, and so is Mounjaro — they are not different drugs, and one is not a stronger version of the other. What differs is what each brand is approved to be prescribed for, which in turn shapes how insurance treats it.

So if you’re searching for tirzepatide’s brand name, there are two correct answers, and which one applies to you depends on why it’s being prescribed.

Tirzepatide side effects

The most common side effects are digestive, and the drug carries a boxed warning — FDA’s most serious warning category. Both Mounjaro and Zepbound carry a boxed warning for risk of thyroid C-cell tumors. That warning appears at the top of both labels: the Mounjaro Prescribing Information and the Zepbound Prescribing Information.

Tirzepatide is contraindicated in people with a personal or family history of medullary thyroid carcinoma (MTC) or with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), per the Zepbound label. StatPearls reports the same contraindication.

The Zepbound label lists these adverse reactions occurring in 5% or more of patients:

• Nausea
• Diarrhea
• Vomiting
• Constipation
• Abdominal pain
• Dyspepsia (indigestion)
• Injection site reactions
• Fatigue
• Hypersensitivity reactions
• Eructation (belching)
• Hair loss
• Gastroesophageal reflux disease (GERD)

That list is the label’s, not ours, and it’s the one worth reading before anything you find in a forum. Most of the digestive effects trace back to the slowed stomach emptying described in the mechanism section above.

Is tirzepatide safe?

“Safe” isn’t a yes-or-no property of a drug — it’s a question about a specific person, a specific condition, and a specific alternative. What can be said accurately: tirzepatide has been through full FDA review for three indications, its adverse-reaction profile is documented in public labeling, and it carries a boxed warning and hard contraindications that rule it out for some people entirely.

No peptide is zero-risk just because it’s naturally modeled on a hormone your body already makes. The label above is the honest starting point for that conversation with a prescriber.

Tirzepatide vs. semaglutide

The short version: semaglutide activates the GLP-1 receptor; tirzepatide activates GLP-1 and GIP, and in the one published head-to-head trial it produced more weight loss. For everything about how semaglutide itself works, see our [semaglutide] entry — we’re keeping this section to the comparison.

In the Lilly-sponsored SURMOUNT-5 trial — 751 patients with obesity and without diabetes, over 72 weeks — tirzepatide produced a mean body weight reduction of 20.2% versus 13.7% with semaglutide (p<0.001). (Aronne LJ et al., N Engl J Med. 2025;393(1):26-36, doi:10.1056/NEJMoa2416394. Note the sponsor: this trial was funded by Eli Lilly and Company, which makes tirzepatide.)

That’s one trial, in one population, funded by the manufacturer of the winning drug. It’s the best direct comparison currently available, and it’s still a single data point — which is a different thing from a settled answer about which drug is right for any individual.

Tirzepatide vs. retatrutide

Until Retatrutide is approved, these two are not in the same regulatory category. Tirzepatide is FDA-approved under two applications (NDA 215866 and NDA 217806) as of September 2026. By contrast, [retatrutide, which is still investigational], is not FDA-approved for any use as of September 2026 — it exists only in clinical research.

If you see them discussed side by side as if they were two options at a pharmacy counter, that framing is wrong. One is a prescribable, labeled drug; the other is a research compound. Our retatrutide entry covers what the early trials actually show.

Compounded tirzepatide: where it stands as of September 2026

Compounded tirzepatide is not FDA-approved, and the regulatory window that allowed pharmacies to compound it during the shortage has closed. FDA determined that the tirzepatide shortage resolved on December 19, 2024. The agency’s period of enforcement discretion for compounders then ended on February 18, 2025 for 503A state-licensed pharmacies and March 19, 2025 for 503B outsourcing facilities. As of an April 1, 2026 update, tirzepatide does not appear on FDA’s drug shortage list or on the 503B bulks list. All of this is documented in FDA’s own statement clarifying policies for compounders as national GLP-1 supply begins to stabilize, as of September 2026.

Two distinctions matter here, and marketing copy tends to blur both.

First: compounded is not a generic, and it is not FDA-approved. In FDA’s words, “compounded drugs are not FDA approved… the agency does not review compounded drugs for safety, effectiveness or quality” — from the agency’s page on concerns about unapproved GLP-1 drugs used for weight loss. That same page reports FDA had received more than 215 adverse event reports involving compounded tirzepatide as of November 30, 2024.

Second: “compounding-eligible during a shortage” was never the same as “approved.” Compounding under FDA’s shortage-era enforcement discretion was a supply workaround, not a finding about the product. Now that the shortage is resolved and the discretion period has ended, that workaround’s basis is gone.

None of that makes a compounded product a crime to possess, and we’re not going to characterize your pharmacy’s paperwork for you. The accurate frame is narrower and more useful: the shortage was resolved, the enforcement-discretion period ended, tirzepatide is not on the shortage list or the 503B bulks list, and a compounded version has not been reviewed by FDA for safety, effectiveness, or quality. If someone is selling you compounded tirzepatide today and describing it as FDA-approved, that claim is false regardless of how the rest of the pitch sounds.

FAQs about tirzepatide