- All four US labels list 3 sites: the abdomen, the thigh and the upper arm, and say drug levels are similar at all three, so no site is better for weight loss.1–4
- The labels ask you to rotate to a new spot every week, and the instructions say to stay at least 2 inches from the belly button.1–4
- Injection site reactions are usually mild. They affected 1.4% of people on Wegovy and 6–8% on Zepbound in weight-loss trials. Swelling of the face or throat, or trouble breathing, needs urgent help.1,3
Where can you inject Ozempic, Wegovy, Zepbound and Mounjaro?
Semaglutide (Ozempic, Wegovy) and tirzepatide (Zepbound, Mounjaro) are injected under the skin, into the fat layer, once a week. Each label's Dosage and Administration section and its Instructions for Use name the same three areas. The details differ a little by product.
| Medicine | Sites in the label | Label notes |
|---|---|---|
| Wegovy (semaglutide) | Abdomen, thigh, upper arm | Lower stomach at least 2 inches from the belly button; rotate sites with each dose |
| Ozempic (semaglutide) | Abdomen, thigh, upper arm | Use a different site each week in the same region; back of the upper arm only with help |
| Zepbound (tirzepatide) | Abdomen, thigh, back of upper arm | Upper arm should be injected by another person; rotate sites each week |
| Mounjaro (tirzepatide) | Abdomen, thigh, back of upper arm | Upper arm by another person; rotate sites each week |
All four labels say not to inject into a muscle or a vein. The Wegovy instructions also say not to inject where the skin is tender, bruised, red or hard, and to avoid scars and stretch marks.1 The Wegovy and Ozempic instructions add that your healthcare provider can help you choose the site that is best for you.1,2
Does the injection site affect how well it works?
Based on the labels, no. Each label's Clinical Pharmacology section (12.3) reports the same finding:
- Semaglutide: the Wegovy and Ozempic labels say similar exposure was achieved with injection in the abdomen, thigh or upper arm. About 89% of an injected dose reaches the bloodstream, with peak levels 1 to 3 days after the dose.1,2
- Tirzepatide: the Zepbound and Mounjaro labels say the same for all three sites. About 80% of the dose reaches the bloodstream, and levels peak 8 to 72 hours after injection.3,4
The Wegovy label also says the injection site can be changed without any change in dose.1 We searched PubMed for published studies comparing semaglutide or tirzepatide levels by site and did not find full reports beyond what the labels summarize. We also found no trial that compared weight loss by injection site.
An older study of exenatide, an earlier GLP-1 medicine, tested this directly. In 28 adults with type 2 diabetes, total drug exposure from the arm was 0.93 times, and from the thigh 0.97 times, that from the abdomen. The authors called the three sites comparable.5 Exenatide is a different drug, so this only supports the general picture.
Why rotate injection sites?
Every label asks for rotation. The Zepbound and Mounjaro instructions explain that you can use the same area of your body, but should pick a different spot in that area each week.3,4 The Ozempic instructions put it as avoiding the exact same spot as last time.2 The labels do not give a reason. Rotation is a long-standing habit with injected medicines, and it also keeps you away from skin that is still sore or bruised from last week.
A simple way to rotate is to cycle through areas in order, for example left abdomen, right abdomen, left thigh, right thigh. With a weekly shot it is easy to forget where the last one went, which is where a log helps.
Injection site reactions: how common are they?
The labels define injection site reactions as things like redness, itching, bruising, pain, rash or hardness at the spot. Rates from the trials summarized in each label's Adverse Reactions section (6.1):
| Medicine | Trials | On the medicine | On placebo |
|---|---|---|---|
| Wegovy | Adult weight-loss trials | 1.4% | 1% |
| Ozempic | Placebo-controlled type 2 diabetes trials | 0.2% | not stated |
| Zepbound | SURMOUNT-1 and -2 pooled, adults with obesity or overweight | 6% (5 mg), 8% (10 mg), 8% (15 mg) | 2% |
| Mounjaro | Placebo-controlled type 2 diabetes trials, adults | 3.2% | 0.4% |
The tirzepatide labels add a detail: reactions were more common in people who developed antibodies to the drug. In the Zepbound weight-loss trials, 11.3% of people with anti-tirzepatide antibodies had injection site reactions, compared with 1% of those without them.3 In the Mounjaro trials, the figures were 4.6% and 0.7%.4
For other stomach and body side effects, see GLP-1 nausea and stomach side effects.
Red, itchy or bruised: when to worry
A small red, itchy or bruised spot is the kind of reaction the labels describe as common. The Zepbound patient information says to talk to your healthcare provider about any side effect that bothers you or does not go away.3
Allergic reactions are different. All four labels warn that serious allergic reactions, including anaphylaxis and angioedema, have been reported. The patient information says to stop the medicine and get medical help right away if you have:1–3
- swelling of your face, lips, tongue or throat
- problems breathing or swallowing
- severe rash or itching
- fainting or feeling dizzy
- a very rapid heartbeat
Related reading
Forgot this week's shot? See what the labels say about missed doses. Comparing medicines? See semaglutide vs tirzepatide.
Common questions
Where is the best place to inject Zepbound for best results?
The US Zepbound label says tirzepatide gives similar drug levels in the blood whether it is injected in the abdomen, thigh or upper arm, so no site is listed as better for results. The label asks people to rotate sites with each weekly dose, and says the back of the upper arm should be injected by another person.
Can you inject Ozempic in the stomach, thigh or arm?
Yes. The US Ozempic label lists the abdomen, thigh and upper arm, and its instructions say to stay at least 2 inches from the belly button. It asks people to use a different spot each week even when they stay in the same body area.
Does injection site affect weight loss on GLP-1s?
The US labels for Wegovy, Ozempic, Zepbound and Mounjaro all say drug exposure is similar in the abdomen, thigh and upper arm. We found no trial that compared weight loss by injection site.
How common are injection site reactions on Wegovy or Zepbound?
In adult weight-loss trials summarized in the Wegovy label, 1.4% of people on Wegovy had injection site reactions vs 1% on placebo. In the two main Zepbound weight-loss trials, 6% to 8% of people on Zepbound had them, depending on dose, vs 2% on placebo.
When should I worry about an injection site reaction?
The labels list redness, itching, bruising and pain as typical injection site reactions. They say to stop the medicine and get medical help right away for signs of a serious allergic reaction, such as swelling of the face, lips, tongue or throat, trouble breathing or swallowing, fainting or a very rapid heartbeat.
Sources
- US prescribing information and Instructions for Use: WEGOVY (semaglutide) injection and tablets. DailyMed, revised 06/2026. Sections 2.1, 5.7, 6.1, 12.3, Medication Guide and Instructions for Use.
- US prescribing information and Instructions for Use: OZEMPIC (semaglutide) injection. DailyMed, checked November 2026. Sections 2.1, 5.8, 6.1, 12.3, Medication Guide and Instructions for Use.
- US prescribing information and Instructions for Use: ZEPBOUND (tirzepatide) injection. DailyMed, revised 08/2026. Sections 2, 5.6, 6.1, 12.3, Medication Guide and Instructions for Use.
- US prescribing information and Instructions for Use: MOUNJARO (tirzepatide) injection. DailyMed, 2026 version. Sections 2, 5.4, 6.1, 12.3 and Instructions for Use.
- Calara F, Taylor K, Han J, et al. A randomized, open-label, crossover study examining the effect of injection site on bioavailability of exenatide (synthetic exendin-4). Clin Ther. 2005;27(2):210-5. doi:10.1016/j.clinthera.2005.02.008 · PubMed
