First week on testosterone: what TikTok gets right and wrong

What did @c.agost actually say?

One week into testosterone gel therapy, Kao described using 1.62% testosterone gel, two pumps daily applied to the outside of each shoulder. The main complaint was residue left on hands after application, which they assumed was "a negligible amount" that washes off. They also flagged the need to avoid skin contact with a girlfriend and two cats until the gel dries.

To be clear: this is gender-affirming hormone therapy, not performance enhancement. That context matters for how we interpret the clinical picture. The creator isn't making extraordinary claims. They're sharing a routine experience and, importantly, raising a real safety question about secondary transfer, even if they framed it casually.

Does the science back this up?

On the transfer question, the concern is legitimate and the FDA takes it seriously. The "negligible amount" assumption deserves more scrutiny than Kao gave it.

The FDA issued a black box warning for testosterone gel products specifically because of secondary exposure risks. Studies have documented virilization in children and partners through incidental skin contact. A 2009 case series published in Pediatrics (Bhatt et al.) documented premature pubic hair and clitoral enlargement in young children whose fathers used testosterone gel and didn't follow transfer precautions rigorously.

The hand residue issue is real, not trivial. Research on AndroGel pharmacokinetics shows that testosterone absorbed through palmar skin is less efficient than deltoid or shoulder application, but the hands do absorb some amount before washing. The FDA recommends washing hands immediately after application, which Kao does, and that does significantly reduce residue. So the "wash it off" behavior is correct, even if calling leftovers "negligible" is an oversimplification.

For cats specifically, veterinary toxicology literature confirms that exogenous androgen exposure in female cats can cause behavioral changes and reproductive abnormalities. This isn't a hypothetical.

What did they get wrong (or right)?

Mostly right, with one soft error. Applying gel to the outer shoulder is consistent with prescribing guidelines for 1.62% formulations like Vogelxo or generic equivalents. Two pumps daily is a standard starting point, and Kao's doctor ordered labs before prescribing, which is exactly how this should work.

The one thing worth pushing back on: describing hand residue as "a negligible amount" is too casual. It's probably a small amount, yes, but the correct framing is: wash hands immediately (Kao does this), avoid contact with others until the site is dry (Kao also does this), and cover the application site before contact. The FDA's guidance doesn't use the word "negligible." It says prevent contact. That's a meaningful difference when you have a girlfriend who could experience hormonal side effects from repeated low-level exposure over weeks or months.

Credit where it's due: most people starting testosterone gel don't think about their pets at all. The cats comment was funny, but it reflects genuine awareness of a real exposure pathway that even some prescribers don't discuss explicitly.

What should you actually know?

If you're starting testosterone gel, the transfer protocol isn't optional fine print. It's the part that protects the people around you. Cover the application site with clothing after it dries (typically 2-5 minutes). Wash hands with soap and water immediately after applying. If a partner or child accidentally contacts the application site, they should wash the exposed skin with soap and water right away.

For people assigned female at birth using testosterone for gender-affirming care, serum testosterone monitoring typically begins 6-8 weeks after starting therapy (Hembree et al., 2017, Journal of Clinical Endocrinology and Metabolism). Gel formulations produce steadier daily levels than injections but require strict adherence to application timing and site rotation.

One week in is genuinely too early to evaluate most clinical outcomes. Voice changes, which Kao is tracking, typically begin appearing between 3-6 months of therapy. Tracking weekly audio is a smart long-game move, even if week one sounds identical to week zero.

Bottom line on this video

This is a pretty responsible first-week check-in. The transfer precautions Kao is taking are correct. The "negligible" framing of hand residue is the one place where more caution would be warranted, not less. Secondary testosterone exposure is documented in humans and animals, and the right word is "minimize," not "negligible." Otherwise, Kao's approach reflects what a well-managed gel protocol actually looks like in practice.