What did @kmartfit actually say?
The creator holds up a bottle of biotin and says it's what he takes "to prevent hair loss on TRT." He takes two pills a day, has been doing it for three years alongside testosterone replacement therapy, and still has "every single hair" on his head. His recommendation: go to Walmart or Amazon, buy biotin for around seven bucks, take it consistently, and "you will notice a difference." That last line is where things get medically dicey. He's presenting his own hairline as proof that biotin works, and recommending it as a solution for TRT-related hair loss. That's a big leap from personal anecdote to medical advice.
Does the science back this up?
Not really, no. Biotin's reputation for supporting hair, skin, and nails is mostly built on marketing, not clinical trials. The evidence that biotin prevents or reverses androgenic alopecia, which is the kind of hair loss TRT can accelerate, is essentially nonexistent.
A 2017 review by Soleymani et al. in the Journal of Drugs in Dermatology looked at all available evidence for biotin supplementation and hair loss. Their conclusion: there's no strong evidence that biotin helps in people who aren't actually biotin-deficient, and true biotin deficiency is rare in healthy adults. The studies that do show hair regrowth with biotin involve people with underlying genetic disorders or severe nutritional deficiencies, not men on TRT with androgenic alopecia.
The mechanism the creator describes, biotin as "building blocks for strong healthy hair," is a loose interpretation of how biotin supports keratin production. That's accurate as far as it goes, but it doesn't translate to preventing DHT-driven follicle miniaturization, which is what TRT can cause in genetically susceptible men.
What did they get wrong, or right?
Let's give credit where it's due: biotin is inexpensive, widely available, and safe at standard doses. There's no meaningful downside to taking it. If someone is biotin-deficient, supplementing absolutely can improve hair quality. The creator isn't recommending anything dangerous here.
But here's what's wrong. He's using his own preserved hairline as evidence that biotin works, and that's a textbook case of survivorship bias. Men on TRT who retain their hair often do so because they weren't genetically predisposed to androgenic alopecia in the first place, not because biotin intervened. His hairline tells us nothing about whether biotin protected it.
More importantly, saying "you will notice a difference" to someone actively losing hair on TRT sets up a false expectation. If the hair loss is driven by DHT acting on genetically sensitive follicles, no amount of biotin is going to stop that process. Finasteride and minoxidil have actual randomized controlled trial data behind them. Biotin does not, for this specific type of hair loss.
What should you actually know?
TRT can accelerate androgenic alopecia in men who carry the genetic predisposition, because exogenous testosterone converts to dihydrotestosterone, or DHT, through the 5-alpha reductase enzyme. DHT binds to androgen receptors in hair follicles and progressively miniaturizes them. This is a hormonal and genetic process, not a nutritional deficiency.
The interventions with real evidence behind them for this type of hair loss are finasteride, which blocks 5-alpha reductase, and minoxidil, which prolongs the growth phase of the hair cycle. A 2020 review by Adil and Godwin in the Journal of the American Academy of Dermatology found minoxidil and finasteride to be the most evidence-supported treatments for androgenic alopecia. Biotin was not among them.
If you're experiencing hair loss on TRT, that conversation belongs with a licensed clinician who can assess your DHT levels, your genetic history, and whether an intervention like finasteride is appropriate for your situation. A $7 bottle of biotin from Walmart is not a substitute for that conversation.