Zepbound is the brand name for tirzepatide, a once-weekly subcutaneous injection from Eli Lilly that activates two incretin receptors: glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). The FDA approved Zepbound in November 2023 for chronic weight management in adults with obesity or overweight with at least one weight-related comorbidity, and again in December 2024 for moderate-to-severe obstructive sleep apnea (OSA) in adults with obesity. It is meant to be used alongside a reduced-calorie diet and increased physical activity.
The Active Ingredient: Tirzepatide
Tirzepatide is a 39 amino acid peptide engineered by Eli Lilly. It is structurally similar to native GIP, with modifications that allow it to bind both the GIP and GLP-1 receptors. By activating both receptors, tirzepatide produces additive effects on insulin secretion, satiety, and gastric emptying. The same molecule is sold under two brand names in the US: Mounjaro for type 2 diabetes and Zepbound for chronic weight management and OSA.
How Zepbound Works
Zepbound drives weight loss through four overlapping mechanisms:
- Slowed gastric emptying. Food leaves the stomach more slowly, prolonging the sensation of fullness after meals.
- Central appetite suppression. GLP-1 receptors in the hypothalamus and brainstem are activated, dampening hunger and reducing food cravings.
- Glucose-dependent insulin secretion. Both GIP and GLP-1 receptor activation enhance insulin release when blood glucose is elevated.
- Reduced glucagon secretion. Less glucagon means less hepatic glucose output and better fasting glucose control.
The dual GIP and GLP-1 mechanism is thought to drive the larger average weight loss observed with tirzepatide compared with GLP-1-only agents. For broader context on how GLP-1 therapies fit into prediabetes care, see our treatment hub.
FDA-Approved Indications
Chronic Weight Management
Per the Zepbound prescribing information, Zepbound is indicated as an adjunct to a reduced-calorie diet and increased physical activity for chronic weight management in adults with an initial BMI of 30 kg/m² or greater (obesity), or 27 kg/m² or greater (overweight) with at least one weight-related comorbid condition such as hypertension, dyslipidemia, type 2 diabetes mellitus, obstructive sleep apnea, or cardiovascular disease.
Obstructive Sleep Apnea
In December 2024, the FDA approved Zepbound for moderate-to-severe OSA in adults with obesity, the first medication ever labeled for OSA in this population. The approval was based on the SURMOUNT-OSA trials, which demonstrated reductions in the apnea-hypopnea index alongside weight loss. The FDA’s announcement details the original weight management approval; the OSA expansion followed roughly a year later.
Dose Schedule
| Phase | Dose | Duration |
|---|---|---|
| Initiation | 2.5 mg weekly | 4 weeks |
| First maintenance option | 5 mg weekly | Maintain or titrate |
| Titration step | 7.5 mg weekly | 4 weeks if higher dose needed |
| Second maintenance option | 10 mg weekly | Maintain or titrate |
| Titration step | 12.5 mg weekly | 4 weeks if higher dose needed |
| Highest maintenance dose | 15 mg weekly | Long-term |
Approved maintenance doses are 5, 10, and 15 mg per week. Titration is intended to reduce gastrointestinal side effects, primarily nausea.
What the SURMOUNT Trials Showed
SURMOUNT-1, published in the New England Journal of Medicine, enrolled 2,539 adults without type 2 diabetes who had a BMI of 30 or higher (or 27 or higher with a weight-related comorbidity). At 72 weeks, mean percentage change in body weight was approximately minus 15 percent at the 5 mg dose, minus 19.5 percent at 10 mg, and minus 20.9 percent at 15 mg, compared with minus 3.1 percent on placebo. SURMOUNT-2 evaluated tirzepatide in adults with both obesity and type 2 diabetes; SURMOUNT-3 added intensive lifestyle intervention; SURMOUNT-4 evaluated continued versus withdrawn therapy; and SURMOUNT-OSA evaluated apnea outcomes.
Common and Serious Side Effects
The most frequently reported adverse reactions in clinical trials include nausea, diarrhea, vomiting, constipation, abdominal pain, dyspepsia, decreased appetite, injection-site reactions, and fatigue during titration weeks. Hair thinning has been reported during rapid weight loss, similar to other obesity therapies.
Serious but less common risks listed in the prescribing information include acute pancreatitis, gallbladder disease, acute kidney injury from dehydration, severe hypersensitivity reactions, hypoglycemia (especially when combined with insulin or sulfonylureas), diabetic retinopathy complications in patients with type 2 diabetes, and acute injury related to suicidal behavior or ideation that should be monitored. The label also carries a boxed warning regarding thyroid C-cell tumors observed in rodent studies.
Who Should Not Take Zepbound
- People with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2.
- People with a known serious hypersensitivity to tirzepatide or any inactive ingredient.
- People who are pregnant; tirzepatide is not recommended in pregnancy, and a washout period is advised before trying to conceive.
- People with severe gastrointestinal disease, including gastroparesis, should discuss the risk-benefit balance with their clinician.
Lifestyle Pairing
Zepbound is approved as an adjunct to a reduced-calorie diet and increased physical activity, not as a stand-alone solution. Adequate dietary protein (often 1.2 to 1.6 g/kg of goal body weight per day) helps preserve lean mass during rapid weight loss. Resistance training two to three times per week supports lean mass and metabolic rate. For glucose context if you have prediabetes, see our overview of A1C levels.
The Bottom Line
Zepbound is the weight-management brand of tirzepatide, a once-weekly subcutaneous dual GIP and GLP-1 receptor agonist from Eli Lilly. It is FDA-approved for chronic weight management in adults with obesity or overweight with a comorbidity, and for moderate-to-severe obstructive sleep apnea in adults with obesity. Average weight loss in late-stage trials reached approximately 21 percent at the 15 mg dose. Like other GLP-1 medications, it carries gastrointestinal side effects, a small set of serious risks, and a boxed warning. Whether Zepbound is the right choice for you is a decision that belongs with your prescriber.
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting, stopping, or changing any medication or treatment plan.
