What did @onehottrail actually say?
The creator claims that finasteride does not meaningfully inflate testosterone levels, citing a meta-analysis to support their position. They argue that modest increases, roughly 10 to 20%, only appear in men with baseline testosterone below 330 ng/dL, and that even those gains amount to "a measly 33 to 66 nadigrams per deciliter." Men above 550 ng/dL, they say, are unlikely to see any change at all.
They also correctly flag that the meta-analysis concluded finasteride and dutasteride use is "not associated with consistent and significant increases in serum testosterone levels." The framing is honest: they're not overselling the effect, and they're upfront that this video exists largely to show their own labs and put the question to rest with data rather than anecdote.
Does the science back this up?
Largely, yes. The meta-analysis the creator references aligns with what the published literature has been saying for years. A 2016 meta-analysis by Belknap et al. in JAMA Internal Medicine, and follow-up work including a 2021 systematic review by Hirshburg et al. in the Journal of Clinical and Aesthetic Dermatology, both confirm that 5-alpha reductase inhibitors produce statistically modest increases in serum testosterone, and those increases are not clinically significant in most eugonadal men.
The mechanism is real: blocking 5-alpha reductase reduces the conversion of testosterone to dihydrotestosterone (DHT), which can slightly reduce negative feedback on the hypothalamic-pituitary-gonadal axis and nudge testosterone up. But the system compensates. In men with normal testosterone, the HPG axis corrects quickly enough that the net effect is small. The creator's instinct to wave off the HPG axis theory talk was probably the right call for this audience, though it does leave out context that would help viewers understand why the baseline level matters so much.
What did they get wrong (or right)?
They got the core claim right. Finasteride does not reliably or significantly raise testosterone, and the 330 ng/dL threshold they cite reflects real data showing that men with hypogonadal or low-normal testosterone are the subgroup most likely to see any measurable bump.
One minor issue: the creator consistently mispronounces nanograms as "nadigrams," which is harmless but worth flagging for credibility. More substantively, they present the 330 ng/dL and 550 ng/dL cutoffs with more precision than the underlying research probably supports. These are thresholds reported in one meta-analysis, not universal clinical benchmarks. The magnitude of testosterone change and which subgroups respond varies across studies depending on assay methodology, age, and baseline DHT levels.
They also don't mention that DHT suppression, not the testosterone change, is the primary hormonal outcome of clinical interest when taking finasteride. For men concerned about hormonal side effects, the DHT reduction (typically 60 to 70% with finasteride, per Hirshburg et al.) is more relevant than the modest testosterone fluctuation the video focuses on.
What should you actually know?
If you're on finasteride for hair loss and worrying about your testosterone levels, the evidence says you probably don't need to. The small increases seen in low-testosterone men are unlikely to push anyone from clinically low into optimal range, and the increases in normal-range men are minimal to nonexistent.
What finasteride does do is suppress DHT substantially. That suppression is why it works for androgenetic alopecia, and it's also why some men report sexual side effects. Those side effects are real, documented in clinical trials, and not explained by the minor testosterone fluctuations this video discusses. If you're monitoring your labs on finasteride, you should be tracking DHT and free testosterone, not just total testosterone, and ideally doing so with a clinician who understands the full hormonal picture rather than relying on a single number from a consumer test.
The creator's bottom line, that finasteride isn't inflating testosterone in any meaningful way, is accurate. But that's not the only hormonal question worth asking when you're on a 5-alpha reductase inhibitor.