Zepbound is an FDA-approved prescription medication used for chronic weight management in adults with obesity or overweight with at least one weight-related health condition. It also has a separate approval for treating moderate to severe obstructive sleep apnea in adults with obesity. The active ingredient is tirzepatide, a once-weekly injection made by Eli Lilly.
FDA-Approved Uses
Zepbound currently has two approved indications. The first, and the one most people are searching about, is chronic weight management. You’re eligible if your BMI is 30 or higher (obesity) or 27 or higher (overweight) with at least one weight-related condition such as high blood pressure, high cholesterol, type 2 diabetes, obstructive sleep apnea, or cardiovascular disease. In both cases, Zepbound is meant to be used alongside a reduced-calorie diet and increased physical activity.
The second approved use came later: treating moderate to severe obstructive sleep apnea in adults with obesity. This made Zepbound the first medication ever approved by the FDA specifically for sleep apnea. In two clinical trials of 469 adults, participants taking Zepbound for 52 weeks experienced significantly fewer breathing interruptions per hour during sleep compared to placebo, and a greater proportion reached remission or mild sleep apnea with symptom resolution. The FDA granted this indication Breakthrough Therapy designation, reflecting how significant the unmet need was.
How Zepbound Differs From Mounjaro
Zepbound and Mounjaro are molecularly identical. Both contain tirzepatide, and both are made by Eli Lilly. The difference is regulatory: Mounjaro is approved for type 2 diabetes, while Zepbound is approved for weight management and sleep apnea. This distinction matters primarily for insurance coverage and prescribing. Your doctor prescribes one or the other based on which condition is being treated.
How It Works in Your Body
Tirzepatide activates two hormone receptors that play key roles in appetite, blood sugar, and metabolism. One is the GLP-1 receptor, the same target that drugs like Wegovy and Ozempic act on. The other is the GIP receptor, which is unique to tirzepatide. By stimulating both pathways, the drug enhances insulin release from the pancreas, improves how your body handles fat storage, and sends stronger fullness signals to the brain. The combined activation of both receptor systems produces a more powerful effect on appetite and weight than targeting GLP-1 alone.
How Much Weight People Lose
The landmark SURMOUNT-1 trial followed adults with obesity (but without type 2 diabetes) for 72 weeks. The results were striking. People on the lowest maintenance dose (5 mg) lost an average of 15% of their body weight. Those on 10 mg lost 19.5%, and those on the highest dose of 15 mg lost 20.9%. The placebo group, which also received diet and exercise counseling, lost 3.1%.
To put that in more concrete terms: in a head-to-head trial called SURMOUNT-5, participants taking Zepbound at its maximum dose lost about 50 pounds on average (20.2% of body weight) over 72 weeks, compared to about 33 pounds (13.7%) for those taking Wegovy at its maximum dose. Nearly one-third of Zepbound users achieved at least 25% body weight reduction, compared to 16% of those on Wegovy. Side effect profiles between the two drugs were similar.
Common Side Effects
Gastrointestinal symptoms are by far the most common side effects, and they tend to be worst during dose increases. Across clinical trials, nausea affected 25% to 29% of people on Zepbound (compared to 8% on placebo). Diarrhea occurred in 19% to 23% of users, and vomiting in 8% to 13%. These rates were fairly consistent across the 5 mg, 10 mg, and 15 mg doses. Most people find that GI symptoms ease as their body adjusts to each new dose level, which is why the medication is increased gradually.
Who Should Not Take Zepbound
Zepbound carries a boxed warning, the FDA’s most serious safety label, related to thyroid cancer risk. In animal studies, tirzepatide caused thyroid tumors in rats. Whether this translates to humans is unknown. The drug is contraindicated if you have a personal or family history of medullary thyroid carcinoma or a condition called Multiple Endocrine Neoplasia syndrome type 2. Symptoms to be aware of include a lump in the neck, difficulty swallowing, shortness of breath, or persistent hoarseness.
Dosing and How It’s Taken
Zepbound is a once-weekly subcutaneous injection, meaning you inject it just under the skin using a pre-filled pen. The starting dose is 2.5 mg per week for the first four weeks. This introductory dose isn’t a treatment dose; it’s designed to let your body adjust. After four weeks, the dose increases to 5 mg. From there, your doctor can raise it in 2.5 mg increments every four weeks or longer, up to a maximum of 15 mg per week. The gradual titration helps minimize side effects, particularly nausea.
For storage, unused pens belong in the refrigerator (between 2°C and 8°C). If you need to travel or can’t refrigerate, a pen can stay at room temperature (up to 30°C) for up to 30 days. Never freeze it. If a pen has been frozen, throw it away.