Testosterone and gender-affirming HRT: what TikTok gets wrong

What did @kai23062 actually say?

Kai ran through a personal comparison of testosterone gel versus injections for trans masculine people on hormone therapy. They described moving from Sustanon (given every four weeks, then adjusted to every eight days) to Nebido, which they now receive every nine weeks instead of the standard 12. Their core argument: the gel-vs-injections debate is overdone, and "it's down to your age, your genetics" rather than one method being universally superior. They also flagged practical issues, including the daily application requirement for gel, sweat affecting absorption, needle phobia, and mood instability before an injection is due, what they call the "man period."

The framing is conversational and experience-based, which is fine. But personal anecdote on a TikTok with 3,100 views can reach people making real decisions about their care, so the details matter.

Does the science back this up?

Partly, yes. The individual-variability argument is well-supported. The claim that one delivery method changes the body "so much quicker" is more complicated than Kai suggests.

On variability: a 2021 review by Irwig in Andrology confirmed that testosterone response in transmasculine individuals varies substantially by individual, with genetics, body composition, and baseline hormone levels all influencing outcomes. So Kai's "it's different for everyone" is not just anecdote, it reflects real pharmacogenomic variation.

On speed of change: the evidence does not strongly support injections as producing faster virilisation than gel when both achieve equivalent serum testosterone levels. A 2019 study by Jacobeit et al. in European Journal of Endocrinology found no significant difference in virilisation timelines between delivery methods when testosterone levels were comparable. The persistent myth that injections are faster probably comes from the fact that injections often produce higher peak levels, not that they are inherently more effective.

The mood instability Kai describes before injection is due, the so-called "man period," is a documented consequence of the trough-peak cycling that comes with longer-acting injections, particularly undecanoate (Nebido). This is not controversial.

What did they get wrong (or right)?

A few things deserve correction. Kai says Sustanon "baseline is supposed to be given every four weeks." Sustanon 250 prescribing guidelines do suggest every three to four weeks in hypogonadal males, but in transmasculine hormone therapy, every two to three weeks is frequently used because the four-week interval often produces significant troughs. The "every four weeks" framing slightly misrepresents standard clinical practice in this population.

They also say Nebido "is a stronger injection." Nebido (testosterone undecanoate) is not stronger in terms of androgenic potency. It is longer-acting because undecanoate is a slower-release ester. Calling it "stronger" is inaccurate and could mislead someone into thinking they need a more potent formulation when what actually differs is pharmacokinetics, not androgenic effect per milligram.

What they got right: the sweating and absorption issue is real. A 2016 study by Grober et al. in Journal of Sexual Medicine confirmed that physical activity and sweating reduce transdermal testosterone absorption meaningfully. The needle phobia point is also a legitimate clinical consideration, not just preference.

What should you actually know?

If you are deciding between gel and injections, the honest clinical picture is this: both can achieve therapeutic testosterone levels. Neither is inherently faster or more effective at producing virilisation when levels are matched. The real differences are practical: adherence requirements, injection anxiety, absorption variability with gel, and the mood cycling that can accompany injections with long trough periods.

The mood instability Kai describes before their injection is due is a known side effect of undecanoate specifically. Some clinicians address this by shortening the interval, which is exactly what happened in Kai's case. That is a reasonable clinical response, not a one-size-fits-all fix.

Dosing intervals in Kai's video reflect their individual clinical management and should not be taken as a template. If you are on hormone therapy and experiencing similar symptoms, the appropriate step is a conversation with your prescriber and a review of your blood results, not adjusting your own schedule based on a TikTok.

• Gel requires consistent daily application at the same time and to skin that will not transfer to others.
• Injections carry the risk of trough-related mood changes, particularly with long-acting formulations.
• Your response to either method will be influenced by individual factors including genetics and body composition.
• A hysterectomy can alter testosterone metabolism, which may explain why Kai's interval changed post-surgery, though this should be verified with your own clinician.