Mounjaro injection sites: what the video gets right and wrong

What did @prettyfrench13 actually say?

The creator told viewers that Mounjaro injections can go into three locations: "your thigh," "your tummy," and "the back of your arms." That is the core of the claim, and it is pretty much correct on the surface. No dosing advice, no medical drama, just a quick rundown of where the needle goes. But the framing skips enough detail that it is worth unpacking what the evidence and the label actually say.

The video was filmed in a casual format, likely in response to a follower question. Short-form health content like this lives and dies by what gets left out, and a few omissions here could matter for someone who is injecting tirzepatide for the first time.

Does the science back this up?

Yes, with caveats. The three injection sites, abdomen, thigh, and upper arm, are exactly what Eli Lilly specifies in the Mounjaro prescribing information. Tirzepatide is administered subcutaneously, meaning into the fat layer just under the skin, not into muscle. All three sites the creator named are standard subcutaneous locations validated in Lilly's phase 3 SURPASS clinical trials.

Pharmacokinetic data from the SURPASS-1 trial (Rosenstock et al., 2021, The Lancet) did not identify meaningful differences in drug absorption across injection sites, which is consistent with what we know about other subcutaneous GLP-1 receptor agonist injections. A 2020 review by Gentilella et al. in Diabetes Therapy examined injection technique across GLP-1 therapies broadly and found site rotation to be an important factor in preventing lipohypertrophy, a thickening of fat tissue that can impair drug absorption over time.

What did they get wrong (or right)?

They got the site list right. Thigh, abdomen, upper arm, those are the three. Credit where it is due.

What they got slightly wrong is the anatomical description. The creator says "the back of your arms," but the approved site is the outer upper arm, specifically the lateral aspect of the upper arm. The back of the arm, the tricep area, is not the recommended location. This is not a trivial distinction. Injecting into the wrong part of the arm increases the risk of hitting muscle rather than subcutaneous tissue, particularly in leaner individuals. The outer upper arm, used for vaccines and insulin alike, has a more predictable fat layer.

The video also does not mention that upper arm self-injection is genuinely difficult without assistance. Lilly's own prescribing information notes that the upper arm site is typically used when someone else is administering the injection. That context is missing entirely, and for a solo injector, that gap could lead to awkward or improper technique.

What should you actually know?

If you are injecting Mounjaro yourself at home, the abdomen and thigh are your most practical options. The abdomen, specifically the area at least two inches from the navel, and the outer thigh are both accessible and have reliable subcutaneous fat layers for most people. Rotate sites within and between these areas to avoid building up scar tissue or lipohypertrophy, which can reduce how well the drug is absorbed.

The upper arm is a valid site but it is harder to reach and harder to pinch correctly on your own. If you are set on using it, have someone help you or ask your prescriber to walk you through technique. Injecting into muscle instead of fat does not just hurt more, it changes the absorption profile of the medication.

One more thing the video skips: avoid injecting into skin that is irritated, bruised, scarred, or has stretch marks. These are standard subcutaneous injection guidelines and they apply to tirzepatide the same as any other injectable medication.