Evidence-graded guideReviewed October 31, 2026

Herbs and Supplements for Hair Growth: Ranked by Evidence

The herbs and supplements with the best evidence for hair growth are rosemary oil (matched 2% minoxidil in one six-month trial), iron (when ferritin is low) and pumpkin seed oil, with saw palmetto a distant and weaker fourth. Everything else on this page, including biotin, collagen and horsetail, is either unproven or only helps if you have a measurable deficiency. That is a shorter list than most supplement pages give you, and it is deliberately so.

This guide is for adults with gradual thinning (androgenetic alopecia, the common pattern type) or shedding that started a few months after a stressor, an illness, a crash diet or childbirth (telogen effluvium). The honest frame is that the strongest hair treatments are not herbs at all: topical minoxidil and, for men, oral finasteride have decades of randomised data, and fixing low iron or an underactive thyroid can stop shedding outright. Herbs are a reasonable add-on or a first step for people who want to avoid drugs, not a replacement for a diagnosis.

See a clinician or dermatologist instead of starting supplements if your hair is coming out in patches, if the scalp is itchy, scaly or scarred, if you have fatigue, cold intolerance or heavy periods alongside the shedding (iron and thyroid checks), or if loss is sudden and heavy. A blood panel (ferritin, TSH, vitamin D, zinc) costs little and tells you which of the picks below is actually worth taking.

Quick answer

  • Rosemary oil — matched 2% minoxidil for hair count at 6 months in a 100-person trial
  • Iron — restores growth when ferritin is low, which is common in women who shed
  • Pumpkin seed oil — 40% increase in hair count vs 10% on placebo in a 24-week RCT
  • Saw palmetto — weak DHT-blocking effect; modest results in small, mostly open-label studies
  • Vitamin D and zinc — worth correcting if deficient; no benefit shown if levels are normal
  • Biotin — only helps the rare people who are actually deficient; otherwise no evidence

The 10 best herbs and supplements for hair growth

Ranked by the strength of human evidence. Strong = multiple trials or a meta-analysis. Moderate = a few small trials. Preliminary = early or animal data.

  1. Rosemary oil

    Moderate evidenceSalvia rosmarinus (Rosmarinus officinalis)

    A 2015 randomised trial in 100 men with androgenetic alopecia compared topical rosemary oil with 2% minoxidil for six months. Both groups had a significant rise in hair count at month six with no difference between them, and scalp itching was more common with minoxidil. It is a single trial without a placebo arm, so it tells you rosemary kept up with a low-dose drug, not that it beats doing nothing. Still, it is the best-designed herbal hair study available.

    Key evidence
    Panahi 2015, 100-person RCT vs 2% minoxidil, 6 months
    Studied dose
    Rosemary essential oil diluted to about 3–5% in a carrier oil (or a ready-made rosemary leave-in), massaged into the scalp daily for at least 6 months
    Best for
    People with pattern thinning who want a non-drug topical, or who cannot tolerate minoxidil's itch
    Cautions
    Undiluted essential oil irritates skin; patch-test first. Avoid getting it in the eyes. Not for use on broken or inflamed scalp, and keep away from young children (ingestion of essential oils is toxic).
    Full Rosemary oil profile

  2. Iron

    Moderate evidence

    Low iron stores are one of the most common reversible causes of diffuse shedding in women, and several case series show telogen effluvium improving once ferritin is restored. Dermatology groups often aim for ferritin above roughly 40–70 ng/mL in people losing hair, even if that is technically within the lab's 'normal' range. Iron does nothing for hair if your stores are already adequate, and excess iron is harmful, so this is a test-then-treat pick rather than a supplement to take on spec.

    Key evidence
    Trost 2006 review (J Am Acad Dermatol) of iron deficiency and hair loss; multiple observational series
    Studied dose
    Only if ferritin is low: 40–65 mg elemental iron (for example ferrous sulfate 200 mg or bisglycinate) once daily or on alternate days with vitamin C, for 3–6 months, then re-test
    Best for
    Women with heavy periods, vegetarians, endurance athletes and anyone shedding diffusely with ferritin under about 40 ng/mL
    Cautions
    Causes constipation and nausea; take away from thyroid medication, levodopa, and some antibiotics by at least 2–4 hours. Do not take without testing: iron overload is possible and dangerous in haemochromatosis. Keep out of reach of children.
    Full Iron profile

  3. Pumpkin seed oil

    Moderate evidenceCucurbita pepo

    A 24-week placebo-controlled trial in 76 Korean men with mild to moderate pattern loss gave 400 mg/day of pumpkin seed oil. Mean hair count rose 40% in the treatment group against 10% on placebo, and blinded photo assessment favoured the oil. A later small study found topical pumpkin seed oil comparable to 5% minoxidil foam in women, though it was tiny. The mechanism is presumed 5-alpha-reductase inhibition, but the data are thin: one decent trial, replicated only partly.

    Key evidence
    Cho 2014, 76-person RCT, 400 mg/day for 24 weeks
    Studied dose
    400 mg/day of pumpkin seed oil in capsules for 24 weeks (the trial used a branded extract with mixed ingredients)
    Best for
    Men with early pattern thinning who want an oral option without finasteride
    Cautions
    Generally well tolerated. The trial used a product that contained other ingredients, so results may not transfer to plain pumpkin seed oil. Mild stomach upset is possible. Stop before surgery as with other oils that may modestly affect platelet function.
    Full Pumpkin seed oil profile

  4. Saw palmetto

    Preliminary evidenceSerenoa repens

    Saw palmetto blocks 5-alpha-reductase weakly in the lab, which is why it is sold as a natural finasteride. The clinical record is thin: a 2020 systematic review found seven studies, most small and open-label, reporting a roughly 60% improvement in hair quality by self-report and a 27% improvement in hair count in one comparative trial. The only head-to-head trial against finasteride (1 mg) found finasteride roughly twice as effective (68% vs 38% improved). Honest summary: it may help a little, and it is clearly weaker than the drug.

    Key evidence
    Evron 2020 systematic review of 7 studies; Rossi 2012 comparison vs finasteride
    Studied dose
    320 mg/day of a standardised liposterolic extract (85–95% fatty acids), for at least 6 months; topical lotions have also been tested
    Best for
    Men who have decided against finasteride and want something, with realistic expectations
    Cautions
    May lower PSA readings, so tell your doctor before prostate screening. Rare reports of liver injury and bleeding; stop two weeks before surgery. Avoid in pregnancy and with anticoagulants. Hormonal effects make it unsuitable for people trying to conceive.
    Full Saw palmetto profile

  5. Vitamin D

    Preliminary evidenceCholecalciferol (D3)

    Low vitamin D is consistently associated with alopecia areata, telogen effluvium and pattern loss in observational studies, and the vitamin D receptor is needed for hair follicle cycling. What is missing is a trial showing that supplementing people with normal levels grows hair. The sensible reading is that deficiency (below about 20 ng/mL or 50 nmol/L) is worth correcting because shedding is one of several reasons to, not that vitamin D is a growth agent.

    Key evidence
    Almohanna 2019 review (Dermatol Ther) of vitamins and minerals in hair loss
    Studied dose
    1,000–2,000 IU/day of vitamin D3 if deficient (higher short courses under supervision), re-test after 3 months
    Best for
    Anyone with low measured vitamin D, dark skin, little sun exposure or alopecia areata
    Cautions
    Doses above 4,000 IU/day long term can raise calcium and are not safer. Interacts with thiazide diuretics and digoxin via calcium. Check levels rather than guessing.
    Full Vitamin D profile

  6. Zinc

    Preliminary evidence

    Zinc deficiency causes hair loss, and several studies in alopecia areata and telogen effluvium found lower serum zinc than in controls. A small Korean study gave 50 mg/day zinc gluconate to 15 alopecia areata patients with low zinc and saw regrowth in 9 of them over 12 weeks, with no control group. There is no evidence that zinc helps hair if your level is normal, and too much zinc depletes copper, which itself causes hair and skin problems.

    Key evidence
    Park 2009, 15-person uncontrolled study in alopecia areata; Kil 2013 serum zinc comparison
    Studied dose
    15–30 mg/day elemental zinc (picolinate or gluconate) for 8–12 weeks if serum zinc is low; take 2 mg copper alongside if continuing beyond that
    Best for
    People with low zinc on testing, restrictive diets, or alopecia areata
    Cautions
    More than 40 mg/day long term causes copper deficiency and anaemia. Separate from quinolone and tetracycline antibiotics and from iron by at least 2 hours. Nausea is common if taken on an empty stomach.
    Full Zinc profile

  7. Nettle root

    Preliminary evidenceUrtica dioica (root)

    Stinging nettle root appears in many hair formulas because it inhibits 5-alpha-reductase and binds sex-hormone-binding globulin in test-tube studies. It has reasonable trial evidence for urinary symptoms in benign prostate enlargement, but no clinical trial has tested it on hair on its own; it has only been studied inside multi-ingredient products. It is here because it is plausible and safe, not because anyone has shown it works for hair.

    Key evidence
    In-vitro 5-alpha-reductase inhibition; no hair-specific RCT
    Studied dose
    300–600 mg/day of a dried root extract, as used in prostate trials; topical rinses are traditional but untested
    Best for
    People building a DHT-focused stack who already use rosemary or pumpkin seed
    Cautions
    Mild diuretic effect; may add to blood-pressure and diabetes medication effects. Avoid in pregnancy. Can cause stomach upset.
    Full Nettle root profile

  8. Omega-3 fish oil

    Preliminary evidence

    A six-month randomised trial in 120 women with female pattern thinning gave omega-3 and omega-6 fatty acids plus antioxidants and found that 62% improved hair density by photographic assessment against 28% on no treatment, with a reduction in the proportion of hairs in the telogen (shedding) phase. The product was a mixture, so the omega-3 contribution cannot be isolated, and the control group received nothing rather than a placebo. Supportive, not conclusive.

    Key evidence
    Le Floc'h 2015, 120-woman RCT, 6 months, mixed omega-3/6 and antioxidant supplement
    Studied dose
    460 mg EPA + 380 mg DHA per day (roughly 1–2 g fish oil) with meals for 6 months
    Best for
    Women with diffuse thinning who also want cardiovascular or skin benefits
    Cautions
    High doses add to the effect of anticoagulants and antiplatelet drugs; stop a week before surgery. Can cause fishy burps and loose stools. Check for mercury-tested products.
    Full Omega-3 fish oil profile

  9. Biotin

    Preliminary evidenceVitamin B7

    Biotin is the most-sold hair vitamin and the least supported. A 2017 review found that every published case of biotin helping hair involved an underlying deficiency, usually from an inherited enzyme defect, long-term antibiotics, pregnancy or heavy raw-egg-white intake. There is no randomised trial showing that biotin grows hair in people with normal levels, and the 5,000–10,000 mcg doses sold are several hundred times the daily requirement.

    Key evidence
    Patel 2017 review (Skin Appendage Disord): 18 cases of benefit, all with deficiency
    Studied dose
    Only if deficient: 2.5–5 mg/day. Normal dietary need is 30 mcg/day
    Best for
    People with brittle nails and hair on long-term antibiotics, anticonvulsants or with a known deficiency
    Cautions
    High-dose biotin interferes with lab tests, including troponin (heart attack tests) and thyroid panels, and can produce dangerously false results. Stop at least 2–3 days before blood tests and tell your clinician you take it.
    Full Biotin profile

  10. Horsetail (silica)

    Preliminary evidenceEquisetum arvense

    Horsetail is the plant source of silica, and the argument for it rests on silicon being a structural component of hair. One nine-month placebo-controlled trial of a stabilised silicic acid (10 mg/day) in 48 women reported stronger hair with a larger cross-sectional area, but no change in hair count or growth rate. A multi-ingredient horsetail-containing product improved hair density in a small sponsored trial. This is a hair-strength story more than a hair-growth story.

    Key evidence
    Wickett 2007, 48-woman RCT of choline-stabilised orthosilicic acid, 9 months
    Studied dose
    10 mg/day of stabilised silicon (orthosilicic acid) or 300–600 mg/day of horsetail extract, for 6–9 months
    Best for
    Fine, breakage-prone hair rather than true thinning
    Cautions
    Horsetail contains thiaminase and can deplete vitamin B1 with long use; avoid in alcohol dependence or with other B1 risks. Mild diuretic; caution with lithium and diuretics. Avoid in pregnancy.
    Full Horsetail (silica) profile

How to choose

  • Get ferritin, TSH, vitamin D and zinc tested first. If any is low, correcting it is the single highest-yield move and makes most of this list irrelevant.
  • If the thinning is pattern-shaped (temples and crown in men, widening part in women), the DHT-related picks apply: rosemary oil topically, pumpkin seed oil orally, and saw palmetto as a weaker third. Expect 6 months before judging.
  • If the shedding started 2–4 months after a trigger (illness, surgery, childbirth, crash diet, new medication), it is probably telogen effluvium and usually resolves on its own within 6–9 months; iron, vitamin D and protein matter more than any herb.
  • If you want the biggest effect and are open to drugs, 5% minoxidil for anyone and finasteride for men outperform every pick here; herbs can be stacked on top rather than used instead.
  • If hair is breaking rather than falling out from the root, look at heat, bleach and tight styles first, then consider silica and collagen, which affect strength rather than count.
  • Skip the shotgun approach of a 20-ingredient hair gummy: it mostly delivers biotin you do not need plus doses of everything else too small to matter.

What to skip

High-dose biotin gummies

No trial shows biotin helps hair in people with normal levels, and 10 mg doses can falsify thyroid and cardiac blood tests. If you take it, stop before any lab work.

Collagen for hair growth

Collagen peptides have modest data for skin elasticity and nail brittleness, but no trial has measured hair count. It is a protein source, not a growth signal.

Castor oil

Popular on social media for lashes and scalp, but there are no clinical trials for hair growth. It is harmless as a conditioner but can cause scalp build-up and, rarely, felting of long hair.

Scalp 'detox' and hair-cleansing teas

Hair loss is not caused by toxins in the scalp, and nothing in these products reaches the follicle in a way that changes the growth cycle.

Safety and when to see a clinician

  • See a clinician if hair falls out in round patches, if the scalp is red, scaly, painful or scarred, if shedding is sudden and heavy, or if you also have fatigue, weight change, cold intolerance or heavy periods. These point to alopecia areata, scalp disease, thyroid problems or anaemia, which supplements will not fix.
  • Do not supplement iron, zinc or vitamin D blind. Iron overload, copper deficiency from zinc, and high calcium from vitamin D are all real; a blood test tells you whether you need them at all.
  • Biotin at supplement doses interferes with troponin, thyroid, vitamin D and hormone assays. Stop it 2–3 days before any blood test and tell the lab.
  • Saw palmetto, pumpkin seed oil and omega-3 can modestly increase bleeding; stop them 1–2 weeks before surgery and discuss with your doctor if you take warfarin, apixaban, clopidogrel or daily aspirin.
  • Saw palmetto, nettle root and other hormonal herbs are not for pregnancy, breastfeeding or anyone trying to conceive. Rosemary essential oil must be diluted and kept away from children.
  • Thyroid medication (levothyroxine) must be taken at least 4 hours apart from iron and calcium, or it will not be absorbed and your hair loss may get worse.

What matters as much as any herb

  • Protein and calories: hair is a low-priority tissue, so crash diets and intakes under about 1 g protein per kg body weight trigger shedding within 2–3 months. Eating enough is more powerful than any supplement.
  • Minoxidil: 5% topical foam or solution has dozens of RCTs and works in both sexes; low-dose oral minoxidil is increasingly prescribed. It is the benchmark every herb is measured against.
  • Finasteride (men) or spironolactone (women, off-label): the only treatments that reliably slow pattern loss over years. A dermatologist can discuss whether the side-effect profile is acceptable for you.
  • Styling and heat: tight braids, extensions and daily heat styling cause traction alopecia and breakage that no oral product reverses. Loosen the style and let the follicle recover.
  • Stress and sleep: major stressors push follicles into the shedding phase; the hair falls 2–4 months later. Managing the trigger, not the shedding, is what shortens the episode.

Frequently asked questions

Which herb is best for hair growth?

Rosemary oil has the best single trial: it matched 2% minoxidil for hair count over six months in 100 men. Pumpkin seed oil has one placebo-controlled trial showing a 40% hair-count increase. Saw palmetto is the most famous but has the weakest data of the three.

Does biotin actually help hair grow?

Only if you are deficient, which is rare outside pregnancy, long-term antibiotic or anticonvulsant use, and inherited enzyme defects. In people with normal levels there is no trial showing any benefit, and high doses interfere with important blood tests.

How long do hair supplements take to work?

Hair grows about 1 cm a month and the cycle is slow, so nothing shows in under 3 months and trials typically run 6 months. Judge any product at 6 months with before-and-after photos in the same light, not by feel.

Can low iron cause hair loss?

Yes, and it is one of the most common correctable causes in women. Ferritin, the storage marker, is the test to ask for; many dermatologists want it above 40–70 ng/mL in people who are shedding, even if the lab flags it as normal.

Is rosemary oil as good as minoxidil?

In one trial it matched 2% minoxidil, which is the weaker strength; most people now use 5%. Nobody has compared rosemary with 5% minoxidil or with placebo, so the honest answer is that it is a reasonable non-drug option, not a proven equal to standard treatment.

Does saw palmetto raise or lower DHT?

It modestly inhibits the enzyme that makes DHT, so in theory it lowers it, but trials show it is far weaker than finasteride: 38% of men improved on saw palmetto versus 68% on finasteride in the only head-to-head study.

What vitamin deficiency causes hair loss?

Iron (ferritin), vitamin D, zinc and, rarely, biotin and vitamin B12. Severe vitamin A excess also causes hair loss, so more is not better. A simple blood panel covers all of them.

References

  1. Panahi Y, et al.. Rosemary oil vs minoxidil 2% for the treatment of androgenetic alopecia: a randomized comparative trial. Skinmed (2015)View source
  2. Cho YH, et al.. Effect of pumpkin seed oil on hair growth in men with androgenetic alopecia: a randomized, double-blind, placebo-controlled trial. Evidence-Based Complementary and Alternative Medicine (2014)View source
  3. Evron E, et al.. Natural hair supplement: friend or foe? Saw palmetto, a systematic review in alopecia. Skin Appendage Disorders (2020)View source
  4. Patel DP, Swink SM, Castelo-Soccio L. A review of the use of biotin for hair loss. Skin Appendage Disorders (2017)View source
  5. Almohanna HM, et al.. The role of vitamins and minerals in hair loss: a review. Dermatology and Therapy (2019)View source
  6. Trost LB, Bergfeld WF, Calogeras E. The diagnosis and treatment of iron deficiency and its potential relationship to hair loss. Journal of the American Academy of Dermatology (2006)View source
  7. Le Floc'h C, et al.. Effect of a nutritional supplement on hair loss in women. Journal of Cosmetic Dermatology (2015)View source
  8. Wickett RR, et al.. Effect of oral intake of choline-stabilized orthosilicic acid on hair tensile strength and morphology in women with fine hair. Archives of Dermatological Research (2007)View source
  9. Biotin: Fact Sheet for Health Professionals. NIH Office of Dietary SupplementsView source
  10. The FDA warns that biotin may interfere with lab tests. U.S. Food and Drug Administration (2019)View source

Related conditions

More guides

Not sure which one fits you?

Ask AskMN. It knows these studies, checks interactions with the medications you tell it about, and it is free and unlimited, no account needed.

Ask about hair growth

This guide is educational and is not medical advice. Herbs and supplements can interact with prescription medicines and are not regulated like drugs. Talk with a clinician or pharmacist before starting anything new, especially if you are pregnant, breastfeeding, have a chronic condition, or take medication.