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GLP-1 / GIP

Tirzepatide

Prepared by the ezGLP team. Sources last checked . Profile reviewed .

Also known as Mounjaro, Zepbound

Routes represented in the knowledgebase: Subcutaneous (SubQ).

Educational overview

Tirzepatide is listed in the ezGLP knowledgebase under GLP-1 / GIP. Evidence and regulatory status can vary by formulation, route, and jurisdiction.

Tirzepatide is a synthetic 39-amino-acid peptide that activates two incretin receptors at once, the glucose-dependent insulinotropic polypeptide (GIP) receptor and the glucagon-like peptide-1 (GLP-1) receptor, and is commonly described as a dual agonist or twincretin. Its backbone is based on the native GIP sequence, modified with non-natural amino acids for enzymatic stability and carrying a C20 fatty diacid chain that binds albumin, which gives an elimination half-life of about five days and supports once-weekly injection. Eli Lilly developed the molecule and markets it as Mounjaro and Zepbound. Combined receptor activity raises glucose-dependent insulin secretion, slows gastric emptying and reduces appetite.

Development ran through the SURPASS trials in type 2 diabetes and the SURMOUNT trials in obesity. SURPASS-2, published in the New England Journal of Medicine in 2021, randomised 1879 adults already on metformin and reported larger reductions in HbA1c and body weight with tirzepatide than with the semaglutide comparator over 40 weeks. SURMOUNT-1 enrolled 2539 adults with obesity or overweight and without diabetes for 72 weeks and reported mean weight reductions of roughly 15 to 21 percent by dose group against about 3 percent on placebo. SURMOUNT-OSA, reported in 2024, studied 469 adults with moderate-to-severe obstructive sleep apnoea and obesity and found reduced apnoea-hypopnoea indices.

The FDA approved tirzepatide as Mounjaro for type 2 diabetes in 2022 and as Zepbound for chronic weight management in 2023, then added moderate-to-severe obstructive sleep apnoea with obesity as a Zepbound indication in late 2024. The European Medicines Agency authorised Mounjaro centrally for both glycaemic control and weight management. Both United States labels carry a boxed warning for thyroid C-cell tumours observed in rodents. Compounded tirzepatide has never been FDA-approved; large-scale copying rested on the shortage listing, and after the agency declared that shortage resolved it restated its warnings about unapproved versions and dosing errors.

Storage and in-use limits come from the individual product label rather than from the molecule. The single-dose pens and vials authorised in the United States are refrigerated, may be held at room temperature for a limited labelled period and are then discarded, with each presentation stating its own figures; labels in other jurisdictions state their own equivalents. Compounded multi-dose vials instead carry a dispensing pharmacy's beyond-use date and a concentration chosen by the compounder. Capturing product name, strength, concentration, manufacturer or pharmacy, lot number and first-use date in an inventory record is what lets a dose log entry be reconstructed afterwards.

Category
GLP-1 / GIP
Routes represented
Subcutaneous (SubQ)
Approximate library half-life
120 hours; formulation-dependent and not dosing guidance
Storage context
Follow the dispensed product label; storage and in-use limits vary by brand and formulation.

Published literature

Safety evidence

Common or reported: nausea, vomiting, diarrhea, constipation, abdominal pain or indigestion, decreased appetite.

Serious or important: pancreatitis, gallbladder disease, dehydration-related kidney injury, severe GI reactions, hypoglycemia with insulin or secretagogues, hypersensitivity.

Product labels also carry thyroid C-cell tumor warnings.

Safety evidence source

Interaction evidence

These are general, pairwise evidence notes. Green identifies the potential-synergy category, while Lv3/Lv2/Lv1 communicates evidence strength; it does not guarantee benefit or cancel a safety warning.

With insulin or insulin secretagogues

Safety flag

Combined glucose lowering increases hypoglycemia risk, including severe hypoglycemia.

Interaction evidence source

With another GLP-1 receptor agonist

Safety flag

Weight-management labels say coadministration with the same active ingredient or another GLP-1 receptor agonist is not recommended.

Interaction evidence source

With narrow-index or threshold-dependent oral medicines

Safety flag

Delayed gastric emptying can alter the timing or extent of oral-drug absorption.

Interaction evidence source

With oral hormonal contraceptives

Safety flag

Tirzepatide-related gastric-emptying delay can reduce oral contraceptive exposure and efficacy.

Interaction evidence source

With Pramlintide

Safety flag

Additive gastric-emptying delay, GI intolerance, and glucose lowering are plausible; a broad clinical contraindication is not established.

Interaction evidence source

Common questions

How long does tirzepatide stay in the body?

The labelled elimination half-life is about five days, which is what supports once-weekly injection. Roughly five half-lives, or about four to five weeks, pass before a final dose is essentially cleared, and steady-state concentrations are reached after about four weeks of continued treatment. Albumin binding through the fatty diacid chain and resistance to enzymatic degradation account for that duration.

Is tirzepatide better than semaglutide for weight loss?

SURPASS-2 compared the two directly in type 2 diabetes over 40 weeks and reported larger reductions in HbA1c and body weight with tirzepatide than with its semaglutide comparator. For obesity the comparison rests mainly on separate trials, SURMOUNT-1 and STEP 1, which differed in population, duration and design; the tirzepatide trial reported larger mean weight reductions. Trial averages describe groups rather than the spread of individual responses.

What is the difference between Mounjaro and Zepbound?

Both contain tirzepatide manufactured by Eli Lilly, so the difference is regulatory rather than chemical. In the United States Mounjaro is approved for glycaemic control in type 2 diabetes, while Zepbound is approved for chronic weight management and, since 2024, for moderate-to-severe obstructive sleep apnoea in adults with obesity. The two carry separate labels and presentations. In the European Union a single brand, Mounjaro, covers both indications.

Is compounded tirzepatide legal?

Compounded tirzepatide is not an FDA-approved product. Copying the approved drug at scale was tolerated while tirzepatide appeared on the FDA drug shortage list; the agency later declared that shortage resolved and set out the dates after which outsourcing facilities and pharmacies could no longer produce essentially identical copies. The FDA has separately warned about dosing errors, salt forms and material from unregistered sources sold as tirzepatide.

What are the side effects of tirzepatide?

The labelled adverse events are predominantly gastrointestinal: nausea, diarrhoea, vomiting, constipation, dyspepsia and abdominal pain, most frequent while the dose is being escalated. Labels also describe pancreatitis, gallbladder disease, acute kidney injury following dehydration, hypersensitivity reactions, diabetic retinopathy complications and hypoglycaemia when an insulin or sulfonylurea is prescribed alongside. A boxed warning covers thyroid C-cell tumours seen in rodents, whose relevance to humans is undetermined.

Further reading

Tools for your existing schedule

These free calculators use values you supply. They do not recommend Tirzepatide, select a dose, or establish a route of administration.

Schedule calendar calculator

Preview and print dose dates and total supply for a schedule, including dose changes you enter yourself.

Supply duration calculator

Estimate how many full doses you have left and when your supply will run out, using your own dose and frequency.

For ongoing records, see ezGLP’s schedule, inventory, and wellness tracking features.

Summarised from published literature for reference only, with citations to the source. Evidence is graded as reported and is not a recommendation to combine, dose, or use any compound.

For personal tracking and education only. Not medical advice, diagnosis, or treatment, and not a medical device. Peptides may be prescription-only or unapproved where you live. Consult a licensed healthcare professional.