Tirzepatide is a 39-amino acid synthetic peptide built on the sequence of glucose-dependent insulinotropic polypeptide (GIP) and engineered to activate two incretin receptors at once — the GIP receptor and the glucagon-like peptide-1 (GLP-1) receptor. A C20 fatty diacid chain attached to the backbone binds circulating albumin, which extends the elimination half-life to roughly five days and makes once-weekly subcutaneous administration possible.
It was the first dual incretin agonist to reach approval, and the first serious evidence that adding GIP receptor agonism to GLP-1 agonism does more than either does alone. Eli Lilly markets it as Mounjaro, approved by the FDA in May 2022 for type 2 diabetes, and as Zepbound, approved in November 2023 for chronic weight management and in December 2024 for moderate-to-severe obstructive sleep apnea in adults with obesity.
Tirzepatide matters on this site as the benchmark. SURPASS-2 put it head to head against semaglutide in type 2 diabetes and beat it on both glycemic control and weight; SURMOUNT-1 reported a mean weight reduction of about 20 percent at 72 weeks in adults with obesity. Every multi-receptor peptide covered here — retatrutide's triple agonism among them — is measured against what tirzepatide already established, which is why its dosing is documented from a prescribing label rather than inferred from a trial.
A once-weekly dual GIP and GLP-1 receptor agonist, approved for type 2 diabetes and for chronic weight management. Research material is supplied as a lyophilised powder that is reconstituted with bacteriostatic water before measurement; the approved products are single-dose pens at fixed strengths and are not measured this way.
| Weeks | Dosage | Syringe units (U-100) |
|---|---|---|
| Weeks 1–4 | 2.5 mg | 25 units0.25 mL |
| Weeks 5–8 | 5 mg | 50 units0.5 mL |
| Weeks 9–12 | 7.5 mg | 75 units0.75 mL |
| Weeks 13–16 | 10 mg | 100 units1 mL |
| Weeks 17–20 | 12.5 mg | 125 units1.25 mL |
| Week 21+ | 15 mg | 150 units1.5 mL |
| Weeks | Dosage | Syringe units (U-100) |
|---|---|---|
| Weeks 1–4 | 2.5 mg | 25 units0.25 mL |
| Weeks 5–8 | 5 mg | 50 units0.5 mL |
| Weeks 9–12 | 7.5 mg | 75 units0.75 mL |
| Weeks 13–16 | 10 mg | 100 units1 mL |
| Weeks 17–20 | 12.5 mg | 125 units1.25 mL |
| Week 21+ | 15 mg | 150 units1.5 mL |
| Weeks | Dosage | Syringe units (U-100) |
|---|---|---|
| Weeks 1–4 | 2.5 mg | 25 units0.25 mL |
| Weeks 5–8 | 5 mg | 50 units0.5 mL |
| Weeks 9–12 | 7.5 mg | 75 units0.75 mL |
| Weeks 13–16 | 10 mg | 100 units1 mL |
| Weeks 17–20 | 12.5 mg | 125 units1.25 mL |
| Week 21+ | 15 mg | 150 units1.5 mL |
FrequencyOnce weekly, subcutaneous, on the same day each week.
For review — two figures here are not settled by a label. No reconstitution volume for tirzepatide is published anywhere on this site, so the water volumes above follow the convention this site already uses for the same 10 / 20 / 30 mg vial ladder, which brings every strength to 10 mg/mL; they are flagged rather than presented as sourced. The week blocks are the earliest escalation the Mounjaro and Zepbound labels permit, not a schedule either label requires: a step may be taken after at least four weeks at the one before it, and many people stay at 5 mg or 10 mg instead of going on.
Every amount in the chart is a step on the titration set out in the Mounjaro and Zepbound prescribing information rather than a figure extrapolated from a trial. The label starts at 2.5 mg once weekly for four weeks and states plainly that this step is for starting treatment and is not intended to be effective on its own; 5 mg is the first maintenance amount; further increases are made in 2.5 mg increments after at least four weeks at the current one, to a maximum of 15 mg once weekly. Approved tirzepatide is supplied in single-dose pens at fixed strengths, so the syringe units here describe only lyophilised research material made up exactly as shown above and correspond to no marking on any pen. All three strengths come to 10 mg/mL as made up above, which is why the units are identical on every chart — a 10 mg vial covers the four 2.5 mg starter weeks and nothing beyond them, a 20 mg vial four weeks at 5 mg, and a 30 mg vial two weeks at 15 mg.
Measurement note. At the water volumes above the largest amount in the chart comes to 150 units, which is more than the 1 mL a 100-unit U-100 syringe holds, so at this concentration the upper steps could not be drawn in a single fill at all.
What this evidence establishes. Tirzepatide is FDA-approved and its dosing is set by a prescribing label rather than inferred from a trial, which puts it in the same class of sourcing as semaglutide on this site. The schedule is a titration whose lower steps exist to manage gastrointestinal tolerability — the label describes 2.5 mg as a starting amount that is not expected to work on its own. Approved products are pre-filled single-dose pens at fixed strengths, so the reconstitution arithmetic above applies only to lyophilised research material. The water volumes are the one figure here with no published source, and they are flagged accordingly.
Sources: Mounjaro (tirzepatide) FDA prescribing information · Zepbound (tirzepatide) FDA prescribing information · SURPASS-2, N Engl J Med 2021 — type 2 diabetes · SURMOUNT-1, N Engl J Med 2022 — chronic weight management
For educational and laboratory research purposes only. It does not provide medical advice, dosing recommendations, or instructions for human or veterinary use. Syringe units assume a U-100 syringe, on which 1 mL is 100 units and a 50-unit syringe holds 0.5 mL.
Tirzepatide binds and activates two class B G protein-coupled receptors. Its affinity for the GIP receptor is comparable to native GIP, while its activity at the GLP-1 receptor is weaker than native GLP-1 — an imbalance that is deliberate, and one of the more interesting design decisions in modern peptide pharmacology.
Amplifies glucose-dependent insulin secretion and acts on adipose tissue, where GIP signaling influences lipid handling and insulin sensitivity
Slows gastric emptying, suppresses glucagon when glucose is high, and reduces appetite and food intake through hypothalamic signaling
Full agonist at the GIP receptor, partial at GLP-1, with reduced beta-arrestin recruitment and less receptor internalization than native GLP-1
A C20 fatty diacid chain binds serum albumin, giving a half-life near five days and a single weekly injection
Insulin secretion is amplified only when glucose is elevated, which is why hypoglycemia is uncommon unless insulin or a sulfonylurea is also being taken
The observed weight effect is driven mainly by reduced energy intake, with trial evidence of improved insulin sensitivity beyond what weight loss alone explains
Clinical significance: The two receptors are not redundant. GIP agonism appears to add weight and glycemic benefit on top of GLP-1 agonism, and there is preclinical evidence that it also blunts the nausea GLP-1 agonism produces — which would explain how tirzepatide reaches larger effects at doses that remain tolerable. That question is still open: the tolerability advantage has not been isolated in humans, and gastrointestinal adverse events remain the most common reason people stop.
Tirzepatide has an unusually complete safety record for a compound on this site: several thousand participants across the SURPASS and SURMOUNT programs, plus a labelled boxed warning and post-marketing surveillance. The contraindications and warnings below are drawn from the FDA-approved prescribing information for Mounjaro and Zepbound.
| Condition / Factor | Risk Level | Rationale |
|---|---|---|
| Personal or family history of medullary thyroid carcinoma, or MEN 2 | CONTRAINDICATED | Boxed warning. Tirzepatide caused thyroid C-cell tumors in rodents; whether it does so in humans is not established. Counsel on symptoms of thyroid tumors, including a neck mass, hoarseness, dysphagia or persistent shortness of breath. |
| Prior serious hypersensitivity to tirzepatide | CONTRAINDICATED | Anaphylaxis and angioedema have been reported. Do not re-expose after a serious reaction. |
| History of pancreatitis | HIGH | Acute pancreatitis was reported in trials. The label advises considering other therapies in patients with a history of it, and discontinuing immediately if pancreatitis is suspected. |
| Concurrent insulin or sulfonylurea | HIGH | Tirzepatide alone rarely causes hypoglycemia because its insulin effect is glucose-dependent, but combined with insulin or an insulin secretagogue the risk is real and the dose of that medicine usually has to be reduced. |
| Pregnancy and breastfeeding | HIGH | Animal reproduction studies show adverse embryo-fetal effects. Weight reduction offers no benefit in pregnancy and may cause harm; the label advises discontinuing when pregnancy is recognized. There are no human data in lactation. |
| Severe gastroparesis or severe gastrointestinal disease | MODERATE | Tirzepatide slows gastric emptying and has not been studied in severe gastroparesis. Persistent, severe gastrointestinal reactions were the most common reason for stopping in trials. |
| Gallbladder disease | MODERATE | Cholelithiasis and acute cholecystitis were reported, a risk shared with rapid weight loss generally. Evaluate gallbladder symptoms rather than attributing them to the injection. |
| Diabetic retinopathy | MODERATE | Rapid improvement in glycemic control has been associated with temporary worsening of retinopathy. Monitor patients with a history of it. |
| Dehydration and renal function | MODERATE | Acute kidney injury has been reported, generally following vomiting, diarrhea or reduced fluid intake. Monitor renal function where severe gastrointestinal effects occur. |
| Oral contraceptives | MODERATE | Delayed gastric emptying reduces the absorption of oral contraceptives. The label advises a non-oral method, or a backup method, for four weeks after starting and after each dose increase. |
| Planned surgery or procedural sedation | MODERATE | Delayed gastric emptying raises the possibility of retained stomach contents under anesthesia. Anesthesia societies have issued guidance on withholding GLP-1 receptor agonists before elective procedures. |
| General safety profile | WELL-CHARACTERIZED | Most common adverse events: nausea, diarrhea, vomiting, constipation, dyspepsia, abdominal pain and injection-site reactions. Mostly dose-dependent, mostly early, and the reason the titration schedule exists. |
FDA: Approved twice under two brand names for the same molecule. Mounjaro was approved in May 2022 for adults with type 2 diabetes; Zepbound in November 2023 for chronic weight management in adults with obesity or with overweight plus a weight-related condition, and in December 2024 for moderate-to-severe obstructive sleep apnea in adults with obesity. Both are once-weekly subcutaneous injections dosed from 2.5 mg to a maximum of 15 mg, and both carry the boxed warning for thyroid C-cell tumors.
EMA: Approved in the European Union as Mounjaro, for type 2 diabetes and, following an extension of the marketing authorization, for weight management. Unlike the United States, the EU markets both indications under the single brand name.
Compounding: While tirzepatide was in shortage, compounded versions were widely available. The FDA declared the shortage resolved and the exemptions that allowed that compounding no longer apply. The agency has documented adverse event reports associated with compounded tirzepatide, including dosing errors traced to unfamiliar concentrations and to syringes marked for something else — the reason this site states the concentration alongside every conversion.
Manufacturer: Eli Lilly and Company (NYSE: LLY), which also developed dulaglutide and is developing retatrutide and orforglipron. Tirzepatide is the compound the rest of that portfolio is now compared against.
Key distinction: Tirzepatide is not a GLP-2 compound and shares nothing with the intestinal GLP-2 analogs beyond a family name. It is a dual GIP and GLP-1 receptor agonist, and the "GLP-2T" label used on this site refers to that dual-receptor generation — one receptor more than semaglutide, one fewer than retatrutide.
Test your understanding of tirzepatide's dual-receptor mechanism, its labelled dosing, and how it differs from the single-receptor agonists.
This profile is for educational and research purposes only. It is not medical advice, and nothing on it is a protocol, a recommendation, or an instruction for use in a person or an animal.
Athena Peptides Education does not prescribe, sell, or recommend any compound. Compounds discussed here are for laboratory research only and are not for human consumption. Always consult a qualified physician before making any decision about your health.