Where to inject for MAXIMUM GLP-1 Weight Loss | Breaking down the data
An internal medicine physician reviews a small injection-site study of tirzepatide and compares it with his own experience of abdomen versus thigh injections.
With Dr. Kevin Joseph (DO)
Key moments
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- 0:00What the video coversJoseph introduces himself and says he will examine whether injection site and rotation affect weight loss and appetite suppression.
- 0:30How GLP-1 drugs workHe explains the difference between GLP-1 agonists and dual GLP-1/GIP agonists and says they act on the pancreas, the hypothalamus and immune cells.
- 1:33The three standard sitesHe lists the abdomen, upper thigh and upper arm as the sites named in the prescribing materials, and says he will compare them.
- 2:37Study design and its limitsHe describes the 54 person, three phase crossover design with a 35 day washout, and criticizes the small sample size.
- 4:19Absorption results by siteHe reports slightly higher uptake and peak concentration from the abdomen, and says the gaps are only a few percentage points with no significance testing shown.
- 6:27Side effects and appetite by siteHe says abdominal injections were associated with more nausea, vomiting and reported appetite reduction than arm or thigh injections.
- 7:27His thigh injection experimentHe recounts trying the thigh after a forum post, getting no appetite suppression and no constipation, and returning to the abdomen.
- 10:34Recommendations on site and rotationHe suggests starting in the abdomen, switching if side effects are severe, and not rotating once a site works for you.
What the video says
Dr. Kevin Joseph, who describes himself as an internal medicine physician and says he has lost over 140 pounds using GLP-1 therapy and peptides, asks whether the injection site changes weight loss or appetite suppression. He starts with a short recap of how GLP-1 and dual GLP-1/GIP drugs work, then lists the three injection areas he says are on the prescribing pamphlet: around the navel, the upper thigh and the back of the upper arm.
The core of the video is his walk through a study he attributes to Eli Lilly. He says it had 54 participants in three groups of 18, with each person receiving tirzepatide at all three sites across three phases, with a 35 day washout between injections. He calls the sample size very small compared with the large obesity trials and says the authors did not report whether the differences were statistically significant. By his reading, the abdomen gave slightly higher drug uptake (24% versus 21% for the upper arm and 22% for the thigh) and a slightly higher peak concentration (about 25% versus 23% and 21%).
Joseph says the more interesting part is the adverse event data. According to his summary, abdominal injections were linked to more nausea and vomiting and to more reported appetite reduction than the arm or thigh, though he notes these are subjective reports. He then describes his own trial of a thigh injection after reading a forum post: he says he had no appetite suppression and no constipation that week, and went back to the abdomen, which brought back both stronger suppression and the constipation.
His conclusions are personal. He suggests starting with the abdomen if weight loss is the goal, trying another site if side effects are severe, and not worrying about rotating once a site works. He says skin and fat are only a delivery vehicle and that he knows of no study showing rotation improves weight loss. He also covers his own low-dose, every 5 days schedule briefly.
On each compound
Tirzepatide2:37
Joseph reviews a study he attributes to Eli Lilly comparing abdomen, thigh and upper arm injections of tirzepatide. He says the abdomen showed slightly higher uptake and more reported appetite suppression along with more side effects, and he shares his own experience at each site.
See how your DNA reads TirzepatideSemaglutide0:30
Joseph names semaglutide brands (Ozempic and Wegovy) as GLP-1 agonists while explaining mechanism of action. He does not discuss semaglutide injection sites in the study.
See how your DNA reads Semaglutide“once you find your sweet spot just stick with it”
What this video doesn’t settle
- The study as described has only 54 participants, and Joseph says no significance testing was reported, so it does not show the site differences matter clinically.
- Appetite and side effect findings were self-reported, and Joseph himself calls them subjective.
- His thigh experiment is one person on a low dose with no control group, so it cannot show how others would respond.
Questions this video answers
Does the injection site affect GLP-1 weight loss?
Joseph says the study he reviews showed only small differences in absorption between the abdomen, thigh and upper arm. He says the best site for weight loss is individual and that the study does not prove a clinically meaningful difference.
Does injecting tirzepatide in the abdomen cause more side effects?
According to Joseph's summary of the study, abdominal injections were linked to more nausea and vomiting and more reported appetite reduction than arm or thigh injections. He notes that these symptoms are subjective.
Do you need to rotate GLP-1 injection sites?
Joseph says he knows of no study showing that rotating sites improves weight loss, and that skin and fat are just a delivery vehicle. He suggests rotating mainly if side effects are debilitating, and otherwise staying with a site that works.
What did the Eli Lilly injection site study find?
Joseph says it had 54 participants and found about 24% uptake from the abdomen, 21% from the arm and 22% from the thigh. He also reports a peak concentration of about 25%, 23% and 21% for those sites respectively.
Why was there a 35 day washout in the tirzepatide study?
Joseph explains that tirzepatide has a half life of 5 days and that about four half lives are needed to clear a dose. He says the 35 day gap avoided cross-reaction between sites and was probably longer than strictly necessary.
Video by Dr. Kevin Joseph, DO on YouTube, embedded as published. The summary is written by PeptidesDNA from the video; every claim in it is the speaker’s. Not affiliated with or endorsed by the creator. Not medical advice.
