What Should Be in a Hair Growth Supplement?
Written by the Fix My Hair Editorial Team · Clinician-reviewed by Dr Hisham Band · GMC No. 7550130 · Last reviewed 12 Jun 2026Most hair supplements are biotin and hope. A few contain ingredients with genuine published evidence. Here is how to tell the difference before you spend £30 a month.
The evidence-based ingredients
A genuinely useful hair supplement contains things that correct deficiencies known to affect hair — not a long list designed to look impressive. The ingredients with real backing:
- Iron — only if you’re low; one of the most impactful for those who need it, useless (and risky) for those who don’t.
- Vitamin D — commonly deficient and linked to hair-cycle health.
- Zinc — needed for hair tissue growth and repair; deficiency causes shedding.
- B vitamins (including B12 and folate) — support healthy growth, especially where diet is limited.
The supporting cast
Some ingredients have weaker or more situational evidence but may help certain people: marine collagen and amino acids (protein building blocks), selenium (in small amounts — too much is harmful), and botanicals like saw palmetto (a weak, inconsistent DHT-blocker). These aren’t headline actors, and a supplement leaning entirely on them is more hope than science.
The biotin myth
Biotin is the poster ingredient of hair supplements — yet genuine biotin deficiency is rare, and supplementing it when you’re not deficient does essentially nothing for hair. Worse, high-dose biotin can interfere with some blood tests (including thyroid and cardiac tests). It’s not harmful in itself, but it’s mostly marketing.
What to ignore
Be sceptical of proprietary “blends” that hide doses, mega-doses of single vitamins, and any product promising to regrow a receding hairline. No supplement reverses androgenetic hair loss — that needs finasteride, minoxidil or surgery. A pill that claims otherwise is selling a story.
The smarter approach
Rather than buying a scattergun supplement and hoping, find out what you’re actually short of. A blood test shows which nutrients are low, so you can target those specifically — far more effective than a generic multivitamin, and usually cheaper in the long run. Supplements work best as precise correction, not blanket insurance.
Common questions
Do hair growth supplements actually work? They help if you have a deficiency they correct; they do little if your levels are already fine, and none reverse genetic loss.
Is biotin worth taking? Only if you’re genuinely deficient, which is rare — and it can skew some blood tests, so mention it before any bloods.
Key takeaways
- Saw palmetto: 83% showed increased density (2025 review)
- Marine collagen: 77% more terminal hairs (RCT)
- Zinc regulates the same enzyme as the medications
- Biotin only helps if you are deficient
- Avoid hidden-dose “proprietary blends”
