Key takeaways:
Zepbound (tirzepatide) is an injectable weight-loss medication. It works by simulating two gut hormones in your body that play a role in appetite and digestion.
In clinical trials, Zepbound helped people who are considered overweight or obese lose 15% to 20% of their starting body weight, depending on the dose. People started seeing weight loss as early as 4 weeks after starting Zepbound.
Stopping Zepbound can cause people to regain weight. It’s intended for long-term use. If you’re interested in stopping the medication, it’s a good idea to discuss it with your prescriber first.
There are ways to save on Zepbound. If you’re eligible, a manufacturer savings card could help you get Zepbound for as little as $25 per prescription.
Save on related medications
Zepbound (tirzepatide) is a once-weekly injectable medication that has made headlines since the FDA approved it in 2023. That’s because it can help people who are considered overweight or obese achieve significant weight loss. And losing weight is a health goal for many people.
If you’re just starting Zepbound, your prescriber likely reviewed the basics of the medication with you. Perhaps you’ve had questions since then. How does Zepbound work for weight loss? And how long will it take to see results? Here, we’ll answer those and other frequently asked questions about Zepbound.
Good to know: Zepbound's manufacturer has a barcode scanning tool online to help you verify that the medication you're taking is legitimate. Using your phone's or computer's camera, scan the barcode on your product. The tool will tell you if it's authenticate Zepbound.
1. How does Zepbound work for weight loss?
Zepbound is unique from other weight-loss injections, such as Wegovy (semaglutide). It’s the first weight-loss medication to target both glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors. So it’s known as a dual GIP/GLP-1 receptor agonist.
GIP and GLP-1 are incretin hormones that your body naturally produces. Among other actions, incretins tell your pancreas to release more insulin after eating. They also help balance the production of new glucose (sugar). And, these hormones affect the passage of food through the gut and regulate feelings of hunger.
Incretins send these messages by attaching to their own special binding sites — the GIP and GLP-1 receptors. Zepbound works by simulating your body’s natural GIP and GLP-1 hormones. But the medication’s effects last longer than your body’s natural incretins.
As a result, Zepbound has the following effects:
Your stomach empties more slowly, causing you to feel fuller for longer.
Your appetite decreases, and you eat less food.
The amount of food cravings you have decreases.
Your pancreas releases more insulin, lowering your blood glucose.
Your liver creates less new glucose.
Together, these effects lead to weight loss and lower blood glucose levels. That’s why tirzepatide is approved as two separate medications: Zepbound for chronic weight management and Mounjaro for Type 2 diabetes. Zepbound is also approved for moderate-to-severe obstructive sleep apnea.
Tips for success: Read these pharmacist-backed tips for using Zepbound (tirzepatide) so you can get the most out of your medication.
What to expect: Learn about notable Zepbound side effects — from nausea to diarrhea — and how to manage them.
Cost considerations: Find out how much Zepbound costs (with and without insurance), plus ways you can save.
2. How long does it take Zepbound to work?
During clinical trials, people taking Zepbound started noticing weight loss about 4 weeks after starting it. This is how long it takes the medication to reach consistent levels in your body. Zepbound’s clinical trial ran for 72 weeks (about 16.5 months). And people continued to lose weight throughout the study. But the greatest results were seen during the first 8 to 9 months of using Zepbound.
3. How long does Zepbound stay in your system?
It takes about 5 days for your body to clear half of Zepbound. This is called its half-life, and it represents when a medication may start wearing off. A half-life also helps experts determine the best dosage for a medication. Zepbound’s half-life of 5 days is why you need to inject it only once a week.
On the flip side, the greater a half-life is, the longer it takes your body to fully clear a medication. In the case of Zepbound, there may be small amounts of it in your system for about 25 days after a dose. This information can be important when it comes to drug interactions. So make sure to include your last Zepbound injection on your medication list when providing it to your healthcare team.
4. How much weight do people lose with Zepbound?
Zepbound is one of the most effective weight-loss medications available. During clinical trials, people lost an average of 15% to 21% of their starting body weight after 72 weeks. This worked out to an average of 34 lbs to 48 lbs. In general, people using the highest Zepbound dose (15 mg) lost more weight than those using lower doses (5 mg and 10 mg).
What’s more, longer use of Zepbound can lead to even more weight loss. People in two different clinical trials saw continued weight loss with longer use — losing an average of 25% of starting body weight. Both studies ran for 72 weeks.
5. How long do you have to take Zepbound?
How long you take Zepbound depends on your health goals. You and your prescriber should work together to determine a length of time that makes sense for you. But Zepbound is intended for long-term use.
Research suggests that people maintain weight loss with continued use of Zepbound. At the end of the clinical trials mentioned above, close to 90% of participants maintained at least 80% of the weight they lost with Zepbound during the first 8 to 9 months (when the greatest weight loss happens).
This study also found that stopping Zepbound can cause you to regain the weight you lost. Participants who switched from Zepbound to placebo (an injection with no medication in it) regained 14% of their body weight. So if you’re going to stop Zepbound, it’s a good idea to develop a plan to help maintain weight loss with your prescriber.
How to save on Zepbound
There are ways to save on Zepbound, which is available as a brand-name medication. If you have commercial insurance, you may be eligible to pay as little as $25 per prescription through the manufacturer’s copay savings program. But if your plan doesn’t cover Zepbound, you may be able to pay $550 for a 30-day supply. Lower-cost single-dose vials are also available through LillyDirect for $349 (2.5 mg) and $499 (5 mg, 7.5 mg, and 10 mg) per month.
The bottom line
Zepbound (tirzepatide) is an injectable weight-loss medication. It works for weight loss by simulating two gut hormones in the body. These hormones play a role in balancing appetite and blood glucose (sugar) levels. You may start to notice initial weight loss about 4 weeks after starting Zepbound.
In studies, people taking Zepbound lost an average of 15% to 21% of their body weight, depending on the dose. And long-term use of the medication can help you maintain this weight loss. But stopping Zepbound can lead to significant weight regain.
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References
Aronne, L. J., et al. (2024). Continued treatment with tirzepatide for maintenance of weight reduction in adults with obesity. JAMA.
Eli Lilly and Company. (2023). FDA approves Lilly’s Zepbound™ (tirzepatide) for chronic weight management, a powerful new option for the treatment of obesity or overweight with weight-related medical problems.
Eli Lilly and Company. (2023). Tirzepatide demonstrated significant and superior weight loss compared to placebo in two pivotal studies.
Eli Lilly and Company. (2024). Zepbound- tirzepatide injection, solution [package insert].
Jastreboff, A. M., et al. (2022). Tirzepatide once weekly for the treatment of obesity. The New England Journal of Medicine.
Lilly Investors. (2025). Lilly launches additional Zepbound vial doses and offers new savings for self-pay patients.
National Center for Biotechnology Information. (2024). PubChem compound summary for CID 163285897, CID 163285897.
