Only a few treatments have solid evidence for pattern hair loss, and they are cheap generics. The market around them is enormous and mostly unregulated, because supplements and cosmetics face a far lower evidential bar than medicines.
That asymmetry is worth holding in mind: the further a product sits from a licensed medicine, the less anyone has had to prove.
Biotin
Verdict: useful only if you are deficient, which is rare.
Biotin deficiency causes hair loss, and correcting it helps. But deficiency is uncommon in people eating a normal diet, and supplementing beyond your needs does nothing for hair.
One genuine hazard: high-dose biotin interferes with laboratory tests, including thyroid function and troponin — the test used to diagnose heart attacks. Tell any doctor arranging blood tests if you take it.
Collagen
Verdict: no good evidence for hair loss.
Hair is made of keratin, not collagen, and ingested collagen is digested into amino acids like any other protein. The marketing rests on plausibility rather than trials in androgenetic alopecia.
Caffeine Shampoo
Verdict: weak evidence, unlikely to harm.
Laboratory work suggests caffeine can counteract some DHT effects on follicles. Translating that into a shampoo left on the scalp for a minute or two is a substantial leap, and the clinical evidence is thin. It is not a substitute for minoxidil or finasteride.
Ketoconazole Shampoo
Verdict: the most defensible of the shampoos.
Primarily an antifungal used for dandruff and seborrhoeic dermatitis. There is some evidence of benefit in androgenetic alopecia, possibly via anti-inflammatory and local anti-androgenic effects. It also genuinely treats scalp inflammation, which does not help hair.
Available over the counter at 1% and on prescription at 2%. Reasonable as an adjunct, not as a primary treatment.
Rosemary Oil
Verdict: interesting, oversold.
A small number of studies have compared rosemary oil with minoxidil and reported broadly comparable results, which is why it circulates so widely online. The studies are small and methodologically limited, and this evidence base is nowhere near minoxidil's. It can also irritate the scalp.
Not unreasonable to try alongside proven treatment. Unreasonable as a replacement for it.
Saw Palmetto
Verdict: weak, and an odd trade-off.
Marketed as a natural DHT blocker. Evidence is limited and well short of finasteride's. Worth noting the logic: people often choose it to avoid finasteride's side effects, but if it works at all it works by the same mechanism — with less data on both efficacy and safety, and no regulated dose.
Microneedling
Verdict: some real evidence, particularly combined with minoxidil.
Studies suggest microneedling with minoxidil outperforms minoxidil alone. Home devices vary enormously in quality and there is an infection risk with poor technique or hygiene. Worth discussing with a professional rather than buying the cheapest roller online.
Where the Money Goes Furthest
If your budget is limited, spend it in this order: a focused blood test to rule out a reversible cause, then generic minoxidil, then finasteride if appropriate for you after a proper discussion of its risks. Those three are where the evidence is.
Supplements bundled into subscription plans are a large share of what people spend and the smallest share of what works. Removing them from a plan is usually the easiest saving available.