Injections, Gels, Pellets, and Pills: Why Injectable Testosterone Remains the Gold Standard

Testosterone replacement therapy can be delivered through injections, transdermal gels and patches, subcutaneous pellets, buccal tablets, nasal gel, and now oral pills — a genuinely wide range of options. According to PubMed, a review of the full landscape of available and emerging TRT options in the U.S. found that all these routes are working toward the same end goal of restoring normal testosterone levels, but each carries a distinct profile of dosing convenience, adverse events, and practical tradeoffs that should inform an individualized choice ([Kresch et al., Expert Opinion on Pharmacotherapy, 2021, PMID: 33866902](https://doi.org/10.1080/14656566.2021.1918101)). Injectable testosterone has earned its "gold standard" reputation for specific, mechanistic reasons worth understanding rather than just accepting as convention. Why Injection Earns the Gold Standard Label Intramuscular or subcutaneous injection delivers testosterone directly into systemic circulation, bypassing two problems that complicate other routes entirely. First, it avoids first-pass liver metabolism — the process by which anything absorbed through the gut gets routed straight through the liver before reaching the rest of the body, which is precisely the mechanism that made older oral testosterone formulations liver-toxic and clinically unusable for decades. Second, because the dose is delivered directly and the substance itself doesn't sit on external skin, it eliminates the transference risk that comes with topical formulations entirely — there's no product on your skin capable of rubbing off onto someone else. Injectable testosterone also has, by a wide margin, the longest clinical track record and the largest body of long-term safety and efficacy data of any delivery route — it's been the default TRT approach for decades, which means its risk profile (including the hematocrit and estradiol dynamics covered in our other TRT articles) is the best-characterized of any option. It's also typically the most cost-effective route, with straightforward, flexible dose adjustment simply by changing the amount or frequency of injections. The Real Cost of Transdermal Gels: Transference This is the risk most casual comparisons undersell, and it's not theoretical. According to PubMed, a review of testosterone exposure in children specifically highlighted secondary exposure to topical testosterone preparations as a real, recurring cause of inappropriate virilization in kids, noting that removing the exposure source typically resolves the hormonal and physical changes ([Cabrera & Rogol, Expert Opinion on Drug Safety, 2013, PMID: 23517636](https://doi.org/10.1517/14740338.2013.782000)). A specific case report described a 2.67-year-old boy who developed pronounced virilization — penile growth, pubic hair, accelerated growth, increased muscle mass — from what was determined to be prolonged, inadvertent contact with his father's topical testosterone cream ([Franklin & Geffner, Journal of Pediatric Endocrinology & Metabolism, 2003, PMID: 12585348](https://doi.org/10.1515/jpem.2003.16.1.107)). This isn't a rare fluke specific to careless application — it's a structurally built-in risk of any product designed to be absorbed through skin: if it's still on the skin surface, it can transfer to whoever makes skin contact, particularly children and partners, before it's fully absorbed. Gels and creams require real behavioral diligence (covering the application site, washing hands immediately, avoiding skin contact for a set period) to manage a risk that injections don't create in the first place. Pellets: Convenience With a Different Kind of Tradeoff Subcutaneous pellets, inserted under the skin (typically in the hip) every few months, solve the daily-compliance problem that gels and frequent injections both create — you don't have to remember anything for months at a time. But per the route-comparison literature, this convenience comes with tradeoffs injections don't have: pellet insertion is a minor surgical procedure with its own risks (infection at the insertion site, and pellets can occasionally extrude, or push back out through the skin), and once inserted, the dose can't be easily adjusted or reversed if levels run too high or side effects emerge — you're committed to that dose until the pellets are surgically removed or fully absorbed over months. Oral Testosterone: A Genuinely Different Story Than It Used to Be Oral testosterone has a legitimately bad historical reputation, and for good reason — older oral formulations (17-alpha-alkylated testosterone, like methyltestosterone) were structurally modified to survive first-pass liver metabolism, and that same modification made them directly hepatotoxic, essentially trading a delivery problem for a liver problem. This has changed meaningfully with a newer formulation: oral testosterone undecanoate, designed to be absorbed through the intestinal lymphatic system rather than going straight through the liver via the portal vein — sidestepping the mechanism that made older oral options dangerous. According to PubMed, a 2-year trial of this newer oral formulation (brand name Jatenzo) found it maintained testosterone in the normal eugonadal range, produced significant improvements in sexual function, and reported no clinically significant changes in liver function tests over the full study period — the specific safety concern that doomed earlier oral options ([Honig et al., Journal of Sexual Medicine, 2022, PMID: 36272969](https://doi.org/10.1016/j.jsxm.2022.09.002)). The same trial did find typical testosterone-related changes shared across delivery routes — a modest blood pressure increase, a hematocrit rise that stayed under the standard 48% threshold, and a decrease in HDL cholesterol — meaning oral TU has solved its historical liver problem specifically, without becoming risk-free in the ways any testosterone therapy carries risk. The study's authors were also appropriately measured, noting that confirmatory head-to-head studies against other TRT formulations would strengthen confidence in its comparative long-term safety. Putting It Together Injectable testosterone remains the reasonable default recommendation for most people specifically because it sidesteps the two most consequential different-route problems entirely — no first-pass liver exposure, and no transference risk — while carrying the deepest, longest safety track record of any option. That's a real, mechanistically grounded reason for its "gold standard" status, not just clinical inertia. That doesn't make the alternatives unreasonable choices for the right person: pellets solve real compliance problems for people who struggle with regular injections or daily gel application, at the cost of dosing flexibility and a minor procedure. Newer oral testosterone undecanoate has genuinely solved the liver toxicity problem that made older oral options a non-starter, giving needle-averse patients a real option that didn't meaningfully exist a decade ago. Transdermal gels remain reasonable for people willing to manage the transference risk diligently, particularly in households without young children. The Bottom Line The differences between TRT delivery routes aren't arbitrary — they trace back to real pharmacological differences in how each method actually gets testosterone into the bloodstream, and those differences directly explain their real-world safety records. Injection avoids first-pass liver metabolism and transference risk simultaneously, which is precisely why it has both the deepest safety data and the "gold standard" reputation. The right choice for any individual still depends on lifestyle, needle tolerance, household composition, and cost — but understanding the actual mechanism behind each route's tradeoffs is a better starting point than assuming they're all functionally interchangeable.