Peptide injection site absorption rates: Do those percentages hold up?

What's this video probably claiming?

Based on the caption, this creator is presenting a ranked hierarchy of subcutaneous injection sites for peptide therapy, with specific absorption rate percentages: abdomen at 90%, thigh at 85%, and upper arm at 75%. The framing suggests these numbers are universal and apply across peptide therapies broadly, from growth hormone secretagogues like CJC-1295 and ipamorelin to repair peptides like BPC-157. The video likely recommends rotation protocols and pinching technique, which is standard injection guidance. On the surface this sounds reasonable. The problem is the specific percentages, which are presented as settled facts. They are not. Anyone citing exact absorption figures for peptides with this level of precision should be showing their receipts, and the receipts here are almost certainly borrowed from insulin pharmacokinetics literature, not peptide-specific research. That's a significant conflation that could mislead users about how these compounds actually behave.

What does the science actually show?

The absorption rate data most commonly cited for subcutaneous injection sites comes from insulin research, not peptide therapy. Koivisto and Felig (1980, New England Journal of Medicine) established that abdominal subcutaneous tissue absorbs insulin approximately 20-30% faster than thigh tissue, which is meaningfully different from claiming precise 90/85/75% figures. A 2014 review in Diabetes Care by Frid et al. examined injection site pharmacokinetics across insulin formulations and found that absorption differences between sites were highly dependent on blood flow, adipose tissue thickness, injection depth, and the specific compound. Peptides like BPC-157 or TB-500 have different molecular weights, receptor targets, and stability profiles compared to insulin. There is no peer-reviewed pharmacokinetic study establishing site-specific absorption percentages for these peptides at the figures being cited. Growth hormone secretagogue research, including work by Ionescu and Frohman (2006, Endocrine Reviews), addresses systemic bioavailability but does not produce the clean ranked percentages this video promotes.

Where does the social media noise diverge from clinical reality?

The biohacking community has a recurring pattern of borrowing insulin injection guidance and applying it wholesale to peptide therapy. The 90/85/75% breakdown circulating on TikTok and Reddit appears to be a simplification of insulin absorption research that has been stripped of its original context and repackaged as universal peptide guidance. Clinical reality is messier. Absorption is affected by individual adipose distribution, injection depth (true subcutaneous vs. inadvertent intramuscular), local tissue vascularity, and the peptide's own half-life. For a short-acting peptide like ipamorelin, with a half-life of roughly two hours, minor site-to-site absorption variation is unlikely to produce clinically meaningful differences in pulse amplitude. For a longer-acting compound like CJC-1295 with DAC, site selection may matter somewhat more, but the evidence base for optimizing this remains thin. Presenting ranked percentages as if they come from controlled peptide trials is misleading, even if the rotation advice itself is reasonable harm-reduction guidance.

What should you actually know?

Rotation of injection sites is legitimate advice with a real evidence base, primarily derived from insulin and low-molecular-weight heparin research. Rotating sites reduces lipohypertrophy, a well-documented complication of repeated subcutaneous injection into the same location, as documented by Blanco et al. (2013, Diabetes Care). The pinch-up technique is also supported for individuals with lower subcutaneous fat to avoid intramuscular injection. These are the parts of this advice worth keeping. What you should discard are the specific percentages. No controlled pharmacokinetic study has produced a 90/85/75% absorption ranking for peptide compounds as a class. If a peptide protocol is being supervised by a licensed provider, site selection should be discussed in the context of your specific compound, your body composition, and your goals. A TikTok caption is not that conversation. Users should also be aware that most peptides discussed under hashtags like peptidetherapy are not FDA-approved for the indications being implied, and compounded versions are not equivalent to any approved reference drug.