Mechanism
A dual agonist.
One molecule activates two incretin receptors — GIP and GLP-1 — instead of just one.
US FDA approved
Tirzepatide
Two receptors. One weekly peptide.
Tirzepatide was the first approved medicine to activate both the GIP and GLP-1 receptors — two hormone pathways the gut uses to manage blood sugar and appetite.
- Targets
- GIPGLP-1
- Dosing schedule
- Once weekly, injected under the skin
- Half-life
- About 5 days
- Brand names
- Mounjaro, Zepbound
Approved uses
- Type 2 diabetes in adults and children aged 10 and older, alongside diet and exercise (Mounjaro)
- Lowering the risk of major cardiovascular events in adults with type 2 diabetes at high risk (Mounjaro)
- Chronic weight management in adults with obesity, or overweight with a weight-related condition (Zepbound)
- Moderate-to-severe obstructive sleep apnea in adults with obesity (Zepbound)
US approvals as of the August 2026 label. Approved uses differ by country; in the Philippines, check the FDA product register.
Developed by Eli Lilly and Company.
A support, not a shortcut.
This is not a magic weight-loss elixir. It works alongside a healthier diet and regular exercise, and only with a doctor's prescription and guidance.
Highlights
Get to know Tirzepatide.
By the numbers
What the trials measured.
How it works
2 receptors. One molecule.
GIP and GLP-1 are incretins: hormones released by the gut after a meal. Tirzepatide mimics both. Acting on two receptors at once produced larger effects on blood sugar and body weight in trials than GLP-1 activity alone.
GIP receptor
Responds to Glucose-dependent insulinotropic polypeptide
- Boosts insulin release when blood sugar is high
- Influences how fat tissue stores and handles energy
- May add to appetite effects and ease nausea alongside GLP-1 (still being studied)
GLP-1 receptor
Responds to Glucagon-like peptide-1
- Boosts insulin release when blood sugar is high
- Lowers glucagon after meals
- Slows stomach emptying
- Signals fullness to the brain
The molecule
Engineered to last.
- Length
- 39 amino acids
- Molecular formula
- C₂₂₅H₃₄₈N₄₈O₆₈
- Molecular weight
- ≈ 4,813 g/mol
- Backbone
- Modelled on the native GIP sequence
- Stability
- Two Aib residues (positions 2 and 13) resist breakdown by the DPP-4 enzyme
- Half-life extension
- C20 fatty diacid attached to lysine 20 through a linker, enabling albumin binding
- Bioavailability
- About 80% after injection under the skin5
Amino-acid sequence
- YPosition 1
- AibPosition 2
- EPosition 3
- GPosition 4
- TPosition 5
- FPosition 6
- TPosition 7
- SPosition 8
- DPosition 9
- YPosition 10
- SPosition 11
- IPosition 12
- AibPosition 13
- LPosition 14
- DPosition 15
- KPosition 16
- IPosition 17
- APosition 18
- QPosition 19
- KPosition 20
- APosition 21
- FPosition 22
- VPosition 23
- QPosition 24
- WPosition 25
- LPosition 26
- IPosition 27
- APosition 28
- GPosition 29
- GPosition 30
- PPosition 31
- SPosition 32
- SPosition 33
- GPosition 34
- APosition 35
- PPosition 36
- PPosition 37
- PPosition 38
- SPosition 39
Aib (non-standard, resists DPP-4) Lysine with C20 fatty-acid side chain
Aib = α-aminoisobutyric acid, a non-standard amino acid. The C-terminus is amidated.
Research
The key trials.
SURMOUNT-1
Phase 3- Who
- 2,539 adults with obesity, or overweight with a related condition, without diabetes
- How long
- 72 weeks
- Compared
- 5, 10 or 15 mg weekly vs placebo
Average body-weight change of −15.0%, −19.5% and −20.9% by dose, vs −3.1% with placebo.1
- Placebo3.1
- 5 mg15.0
- 10 mg19.5
- 15 mg20.9
SURPASS-2
Phase 3- Who
- 1,879 adults with type 2 diabetes taking metformin
- How long
- 40 weeks
- Compared
- 5, 10 or 15 mg weekly vs semaglutide 1 mg
HbA1c fell by 2.01, 2.24 and 2.30 percentage points by dose, vs 1.86 with semaglutide 1 mg.2
SURMOUNT-5
Phase 3b- Who
- Adults with obesity, without diabetes
- How long
- 72 weeks
- Compared
- Highest tolerated tirzepatide dose vs highest tolerated semaglutide dose
Average weight loss of 20.2% with tirzepatide vs 13.7% with semaglutide.3
SURMOUNT-OSA
Phase 3- Who
- Adults with obesity and moderate-to-severe obstructive sleep apnea
- How long
- 52 weeks
- Compared
- Highest tolerated dose vs placebo, with and without CPAP
Breathing events per hour of sleep fell by about 25–29, vs about 5 with placebo.4
Safety
What to know about side effects.
Most common
- Nausea
- Diarrhea
- Vomiting
- Constipation
- Decreased appetite
- Indigestion
- Stomach pain
Digestive side effects are most common while the dose is being increased and tend to ease over time.
Warnings on the label5
Thyroid C-cell tumors
Boxed warning: caused thyroid C-cell tumors in rats. Not for people with a personal or family history of medullary thyroid carcinoma or MEN 2.
Pancreatitis
Severe, persistent stomach pain needs prompt medical attention.
Gallbladder problems
Including gallstones, particularly with rapid weight loss.
Low blood sugar
Risk rises when combined with insulin or a sulfonylurea.
Kidney problems
Dehydration from vomiting or diarrhea can worsen kidney function.
Birth control pills
May work less well; use a non-oral or added barrier method for 4 weeks after starting and after each dose increase.
Anaesthesia and sedation
Slower stomach emptying raises the risk of inhaling stomach contents. Tell your care team before any procedure.
This is a summary, not a complete list. Only a qualified healthcare professional can say whether a medicine is appropriate for someone.
Timeline
From lab to clinic.
2018
Phase 2 results in type 2 diabetes published.
May 2022
FDA approves Mounjaro for type 2 diabetes.
Jun 2022
SURMOUNT-1 obesity results published in NEJM.
Nov 2023
FDA approves Zepbound for chronic weight management.
Dec 2024
FDA approves Zepbound for obstructive sleep apnea in adults with obesity.
2025
SURMOUNT-5 head-to-head results vs semaglutide published.
Dec 2025
Mounjaro approved for type 2 diabetes in children aged 10 and older.
2026
Philippine FDA warns against unregistered "research use" tirzepatide vials.
Aug 2026
Mounjaro label adds lowering cardiovascular-event risk in type 2 diabetes.