TRT injection site choices: what the evidence actually shows

What did @joinfeel30 actually say?

The creator argued that injection site choice for TRT comes down primarily to volume, placing the deltoid at one milliliter maximum, the thigh as the easiest self-injection site, and the glute as the go-to for clinic-administered shots. They said "most TRT dosing is never gonna be bigger than one ml" and framed the whole decision as a practical convenience question.

The framing is reasonable for a short-form video. Nothing here reads as reckless. But the claim that volume is the main driver of site selection oversimplifies what's actually a multi-factor decision involving absorption kinetics, tissue depth, patient anatomy, and injection technique. Convenience matters, but calling it the primary variable is a stretch.

Does the science back this up?

Partly. The deltoid volume limit of roughly one milliliter is consistent with clinical guidance, and the vastus lateralis being easier for self-injection is well-supported in nursing and endocrinology literature. Where the video falls short is in treating these as the only relevant considerations.

A 2021 review by Cook and Collins in the Journal of Advanced Nursing identified tissue depth, muscle mass, and injection angle as independent variables affecting drug absorption and patient comfort, separate from volume. Research on intramuscular testosterone pharmacokinetics, including a 2013 study by Behre et al. in Andrology, found measurable differences in peak serum testosterone levels depending on injection site, though these differences were modest in most patients. The video does not mention absorption differences at all, which is a real omission for a platform discussing clinical outcomes.

What did they get wrong (or right)?

They got the basics right. The deltoid one-milliliter cap is accurate and consistent with standard pharmacology references. The vastus lateralis recommendation for home self-injection is genuinely evidence-backed. Nurses and patients in multiple studies report lower pain scores and greater confidence with thigh injections compared to ventrogluteal or dorsogluteal sites when self-administering.

What they got wrong, or at least incomplete: the video implies the glute is primarily a "professional" site because of access difficulty, but the dorsogluteal site (the traditional "glute" injection) has actually fallen out of favor in many clinical settings due to proximity to the sciatic nerve and variable tissue depth. The ventrogluteal site is now preferred by many practitioners over the dorsogluteal. Lumping these together as just "the glute" matters clinically. The creator also never mentions the ventrogluteal site, which several injection safety guidelines now recommend as the preferred IM site for adults.

The phrase "it can be a little bit cumbersome" undersells legitimate safety concerns around dorsogluteal self-injection, including nerve injury risk.

What should you actually know?

Injection site selection for TRT involves more than reach and volume. Tissue depth varies significantly by body composition. A patient with higher adipose tissue may inadvertently inject subcutaneously rather than intramuscularly, which changes absorption and can cause local reactions. A 2019 study by Nicoll and Hesby in Medsurg Nursing found that subcutaneous accidental injection during intended IM administration occurred in a meaningful proportion of patients, particularly at the dorsogluteal site.

The ventrogluteal site is backed by multiple safety reviews as reducing nerve and vascular injury risk compared to dorsogluteal. It is also accessible for self-injection with practice, contrary to the implication that the glute is only practical in a clinical setting. If you are doing at-home TRT injections, this site is worth discussing with your provider. Site rotation also matters for long-term tissue health, a topic the video skips entirely. Injecting the same site repeatedly causes lipohypertrophy and can alter absorption unpredictably over time.