GLP-1 injection sites: where to inject and how to rotate

GLP-1 injections go under the skin (subcutaneously) of the stomach, the thigh or the upper arm. The labels for Zepbound, Mounjaro, Wegovy and Ozempic all list those three areas, all report similar drug levels from each one, and all tell you to use a new spot every week.

The differences are small but worth knowing: who should inject the back of the arm, how far to stay from the belly button, and what to do if you also take insulin. Here is what each label and its Instructions for Use say.

Where each label says to inject

Scroll sideways to see the full table

Sources: Zepbound label section 2.4 and Instructions for Use (rev. 08/2026); Mounjaro label section 2.2 and Medication Guide (rev. 08/2026); Wegovy label section 2.1 and Instructions for Use (rev. 06/2026); Ozempic label section 2.1, Medication Guide and syringe Instructions for Use (rev. 05/2026).

Every label says the shot goes under the skin only. The Zepbound and Wegovy Medication Guides add: do not inject into a muscle or a vein.

Why the upper arm has a “with help” note

The Zepbound and Mounjaro labels say “another person should inject in the back of the upper arm.” The back of your own arm is hard to see and reach, so a caregiver gives that shot. Wegovy’s single-dose pen instructions list the “upper arm” without that note, while the Wegovy and Ozempic prefilled syringe instructions say “back of upper arm (only with help from someone else).” If you inject alone, the stomach and thigh are the two sites every label lets you use yourself.

Does the site change how much medicine you absorb?

Not in a way the labels report. Each label’s pharmacology section makes the same point:

• Zepbound and Mounjaro: “Similar exposure was achieved with subcutaneous administration of tirzepatide in the abdomen, thigh, or upper arm.”
• Wegovy: “Similar exposure was achieved with subcutaneous administration of semaglutide in the abdomen, thigh, or upper arm.”
• Ozempic: “Similar exposure is achieved” in the same three areas.

The Wegovy label goes one step further: “The time of day and the injection site can be changed without the need for a dosage modification.” No label names a best site for weight loss. Pick the area you can reach comfortably and inject correctly, then rotate.

Both drugs last long enough that the exact hour and site matter less than the weekly rhythm. Tirzepatide’s half-life is about 5 days, and semaglutide’s is about 1 week, according to their labels.

How to rotate injection sites

The Zepbound Medication Guide says to “change (rotate) your injection site with each weekly injection. You may use the same area of your body but be sure to choose a different injection site in that area.” The Wegovy, Ozempic and Mounjaro instructions say the same thing in their own words.

Rotation has a reason. The Zepbound vial instructions say rotating within the area you choose lowers your risk of lipodystrophy (pits or thickened skin) and localized cutaneous amyloidosis (lumps under the skin) at the injection sites.

One way to keep track: picture your stomach as four squares around the belly button, keeping at least 2 inches clear of it, and move to the next square each week. Or alternate left thigh and right thigh. Writing the site in a calendar next to the dose date takes ten seconds and saves guessing.

If you also inject insulin

The Mounjaro and Ozempic Medication Guides say you may give the GLP-1 and insulin “in the same body area (such as your stomach area), but not right next to each other.” Never mix them in one syringe. The Zepbound vial instructions say not to inject Zepbound in the same site used for other medicines.

Spots to skip

The instructions list places not to inject:

• Skin that is tender, bruised, red, scaly or hard (Zepbound and Wegovy instructions).
• Scars, damaged skin or stretch marks.
• Skin with pits, thickening or lumps, which can be signs of the skin changes rotation is meant to prevent.
• Within 2 inches of the belly button, in the Wegovy and Zepbound KwikPen instructions.

If you have trouble getting the pen to work, the Wegovy instructions suggest switching to a firmer site, such as the upper leg or upper arm, or standing up while injecting into the lower stomach. If a little blood appears after the shot, press the spot lightly with gauze or a cotton ball and do not rub it.

Injection-site reactions

Redness, itching, bruising or pain where the needle went in is the most common local problem. Rates from each label, drug vs placebo:

On Zepbound, reactions were more common in people who developed antibodies to tirzepatide (11.3%) than in those who did not (1%). Rotating sites, injecting into healthy skin and using a new needle each time are the steps the instructions give. Tell your clinician if a reaction is spreading or does not settle. Swelling of the face, lips, tongue or throat, trouble breathing or swallowing, or a very rapid heartbeat can mean a serious allergic reaction; the Zepbound Medication Guide says to stop the medicine and get medical help right away.

Compounded GLP-1 injections

Compounded semaglutide and tirzepatide are not Wegovy or Zepbound, and not generics of them. A compounding pharmacy prepares them, and they aren’t FDA-approved. The FDA says it does not review compounded drugs for safety, effectiveness or quality before they are sold (FDA, updated Oct 1, 2026).

The site guidance above comes from the brand-name labels. For a compounded vial, follow the instructions from your prescriber and the dispensing pharmacy, including the syringe size and how to measure your dose. The FDA has also reported fake products labeled as compounded tirzepatide from pharmacies that did not make them; one adverse event report described redness, swelling, pain and a red lump at the injection site. Get compounded medication only from a licensed pharmacy your prescriber names. Our guide to whether compounded semaglutide is legal and safe has more.

Safety: the boxed warning comes first

Zepbound, Mounjaro, Wegovy and Ozempic each carry a boxed warning for thyroid C-cell tumors. Semaglutide caused these tumors in mice and rats, and tirzepatide in rats; it is unknown whether they do in humans. None of these drugs is for people with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Tell your clinician about a lump in the neck, trouble swallowing, shortness of breath or hoarseness that won’t go away.

The labels’ other warnings include severe stomach problems, kidney injury from dehydration, gallbladder disease, pancreatitis, serious allergic reactions, low blood sugar with insulin or a sulfonylurea, and a risk of breathing in stomach contents under anesthesia. Never share a pen, including the multi-dose KwikPen, Wegovy FlexTouch or Ozempic pen, even with a new needle. Put used needles and single-dose pens in an FDA-cleared sharps container right away, as the Instructions for Use say (FDA sharps guidance). Our GLP-1 side effects guide has the label rates.

The bottom line

Inject your GLP-1 under the skin of your stomach or thigh, or the upper arm where your label allows it, and move to a new spot every week. The labels show similar drug levels from every site, so choose the one you can reach and inject well. For step-by-step help with each Zepbound device, see how to inject Zepbound. When you are ready to compare programs that prescribe these medications, see our list of GLP-1 providers.