Every GLP-1 pen label in the US names the same three sites: the abdomen, the thigh and the upper arm. The Zepbound, Mounjaro and Wegovy labels state that similar drug exposure was achieved at all three, so no site is “stronger.” The labels differ on smaller points — who should inject the arm, how to rotate, and whether you can inject next to insulin — and those differences are what this page sets out.
The three sites, and what the labels say about absorption
The tirzepatide labels put it in one sentence: inject “in the abdomen, thigh, or another person should inject in the back of the upper arm.” The Wegovy label lists “the abdomen, thigh, or upper arm” and adds that “the time of day and the injection site can be changed without the need for a dosage modification.”
On absorption, the clinical pharmacology sections of Zepbound and Mounjaro say “similar exposure was achieved with subcutaneous administration of tirzepatide in the abdomen, thigh, or upper arm,” and the semaglutide labels say the same of semaglutide. That is the evidence-based answer to “which site works best”: for these drugs, the measured difference was not large enough for the label to distinguish them.
The one exception with a number attached is liraglutide. The Victoza label reports that exposure from the thigh was 22% lower than from the abdomen, and still concludes that exposure was comparable across the three sites. It is the only label in this group that prints a site difference at all.
Label by label
The upper arm: who should inject it
This is where the labels genuinely disagree. Zepbound and Mounjaro say in the prescribing information itself that another person should inject the back of the upper arm, and the pen instructions repeat it: “Another person can inject into the back of your upper arm.” The Wegovy, Ozempic, Saxenda and Victoza prescribing information lists the upper arm with no such condition, though some of their device instructions add one — the Ozempic single-dose syringe says “back of upper arm (only with help from someone else).”
The practical reason is reach. The back of the arm is hard to pinch and inject at the right angle on yourself, which is why the instructions steer self-injectors to the abdomen and thigh.
Rotation: same area, different spot
Every label says to rotate, and none of them means “switch body part every week.” The Zepbound Medication Guide says “you may use the same area of your body but be sure to choose a different injection site in that area,” and the Wegovy pen instructions: “You may inject in the same body area each week, but make sure it is not in the same spot each time.” The liraglutide labels say to rotate within the same region specifically to reduce the risk of cutaneous amyloidosis.
The tirzepatide single-dose vial instructions give the reason in full: rotate “to reduce your risk of getting lipodystrophy (pits in skin or thickened skin) and localized cutaneous amyloidosis (skin with lumps) at the injection sites.” The same instructions say not to use a site used for other medicines.
The 2-inch rule
“At least 2 inches from the belly button” is real, but it lives in the device instructions rather than the prescribing information: the tirzepatide KwikPen, the Wegovy pens (“keep a distance of 2 inches (5 cm) from your belly button”) and the Ozempic syringe all state it. No prescribing information section does.
Injecting near insulin
Mounjaro, Ozempic and Victoza say the same thing: it is acceptable to inject the drug and insulin in the same body region, but the injections should not be adjacent to each other. Mounjaro adds to administer them as separate injections and never mix. Zepbound, Wegovy and Saxenda — the weight-management brands — do not address insulin co-injection.
Under the skin, not into muscle
All six are subcutaneous injections. Each Medication Guide states not to inject into a muscle or a vein. Timing does not interact with site: Zepbound and Mounjaro can be given at any time of day, with or without meals, and the semaglutide labels say the same with the added instruction to keep to the same day each week.
If you draw from a vial
The sites are the same for a vial-and-syringe product, but the volume is now something you measure. Get that from how to read an insulin syringe and the tirzepatide or semaglutide calculator, which work from your own vial concentration.