Last updated: March 2026 — Written by the ORVOVA team, reviewed by our dermocosmetics advisor.
The supplement aisle at your pharmacy is a minefield. Dozens of boxes, every one of them promising something: "stronger hair", "proven anti-hair-loss", "visible regrowth". Prices run from 8 to 60 euros. And the sales assistant is just as lost as you are.
The reality: some supplements have solid clinical data behind them. Others are pure marketing built on a scientific base that doesn't exist. And most sit in a grey zone where the formula is reasonable but the dose is too low, or the right ingredient is there in a form your body can't absorb.
This article breaks the actives down one by one, with effective doses, the forms worth choosing and the ones you can happily skip.
Contents
- How hair supplements actually work
- The actives with solid evidence
- The popular but overrated actives
- Emerging actives: promising but unproven
- The combined approach: inside + outside
- How to choose a hair supplement: the checklist
- The blood test to run before any supplementation
- The verdict: pragmatism over marketing
- Frequently asked questions
How hair supplements actually work
Before we talk ingredients, one fundamental principle has to be clear: hair is a non-essential tissue.
Your body has priorities. The heart, the brain, the liver, the muscles — they all get their nutrients first. Hair and nails come last in the metabolic queue. Which means that even a mild deficiency, long before it causes classic clinical symptoms, can already show up as hair loss or slower growth.
That's the basic principle behind hair supplements: filling in the subclinical deficiencies that are starving the hair follicle. Not magically boosting growth — simply giving hair what it needs to grow normally.
What the hair follicle consumes
The follicle is one of the most metabolically active tissues in the body. Hair grows around 1 cm a month, which requires intense cell division in the follicular matrix. That activity demands:
- Iron — to carry oxygen to the dermal papilla
- Zinc — for protein synthesis (hair is made of keratin, a protein)
- Biotin — a coenzyme involved in keratin synthesis
- Sulphur amino acids — the building blocks of keratin (methionine, cysteine)
- Vitamin D — regulator of the follicular cycle
- Essential fatty acids — for the follicle's cell membranes
[Image: The hair cycle and the essential nutrients at each growth phase]
The actives with solid evidence
Iron: the number one hair deficiency
This is the deficiency most frequently linked to hair loss, particularly in women. Several studies show that ferritin (the body's iron store) is significantly lower in women with telogen effluvium than in controls.
The optimal threshold for hair is higher than the standard clinical threshold. Most labs class ferritin as "normal" from 12-15 ng/mL. But trichologists recommend a minimum of 40 ng/mL, ideally 70 ng/mL, for optimal hair growth.
Form to choose: iron bisglycinate (better absorption, fewer gastrointestinal side effects) or liposomal iron. Avoid ferrous sulphate, which causes constipation and irritates the stomach.
Effective dose: 14 to 28 mg of elemental iron a day if a deficiency has been documented. Never supplement iron without a blood test first — excess iron is toxic (haemochromatosis).
Zinc: essential but double-edged
Zinc is involved in cell division, protein synthesis and immune function — three pillars of hair health. Zinc deficiency causes well-documented hair loss, along with brittle nails and slower wound healing.
The catch: excess zinc depletes copper, which causes... hair loss. Zinc supplementation is a delicate balance.
Form to choose: zinc bisglycinate or zinc picolinate (better bioavailability than the zinc oxide found in budget formulas).
Effective dose: 15 to 30 mg a day, maximum. Beyond that, supplement copper too (1-2 mg) to avoid depletion.
Vitamin D: the overlooked regulator of the hair cycle
Research over the past decade has revealed vitamin D's central role in the follicular cycle. VDR (Vitamin D Receptor) receptors are present on dermal papilla cells and take part in triggering the anagen (growth) phase.
In temperate countries, up to 80% of the population is vitamin D insufficient between October and April. It's probably one of the drivers of seasonal autumn shedding.
Form to choose: vitamin D3 (cholecalciferol), not D2. In an oil format for better absorption (it's a fat-soluble vitamin).
Effective dose: 1,000 to 4,000 IU a day depending on your blood level. Target: 40-60 ng/mL (25-OH-D3 blood test).
[Image: Bioavailability compared across the different forms of iron, zinc and vitamins]
The popular but overrated actives
Biotin: the most lucrative myth
Biotin (vitamin B7/B8) is THE star ingredient in almost every hair supplement. It's also the one with the weakest efficacy evidence in people who aren't deficient.
The problem: biotin deficiency is extremely rare in the general population. Biotin is produced by gut bacteria, present in plenty of foods (eggs, liver, nuts) and daily requirements are low (30 mcg).
Supplements are often dosed at 5,000-10,000 mcg, which is 150 to 300 times the recommended intake. At those doses, biotin has shown no additional hair benefit in people with normal status. It can even skew the results of certain blood tests (thyroid, cardiac troponin) — an underestimated risk.
When it genuinely works: in the rare people with a true deficiency (antiepileptic treatment, excessive raw egg white consumption, certain genetic conditions). For everyone else, it's a 30-euro-a-month placebo.
Brewer's yeast: pleasant but limited
Brewer's yeast (Saccharomyces cerevisiae) provides B-group vitamins, amino acids and minerals. It's an honest "general" supplement, but not a hair specialist. Its nutritional profile is useful for vegetarians (rich in B12), but the zinc and iron doses are far too low to correct a hair-related deficiency.
Spirulina: good for health, modest for hair
Spirulina is a superfood rich in protein, iron and antioxidants. But spirulina's iron (non-haem iron) has mediocre bioavailability, and the amounts of zinc and biotin are too low for any specific hair impact. It's a good general supplement, not a targeted treatment.
You might also like this article: biotin for hair.
Emerging actives: promising but unproven
Vitamin E (tocotrienols)
A 2010 study (Beoy et al.) showed that tocotrienols (a specific form of vitamin E) increased hair count by 34% in supplemented subjects over 8 months. Small study (38 participants), but an encouraging result. Tocotrienols are found in palm oil, brown rice and barley.
Ashwagandha (Withania somnifera)
This ayurvedic adaptogen lowers cortisol (the stress hormone) by an average of 30% in clinical studies. Chronically elevated cortisol prolongs the catagen phase and pushes follicles into telogen — the mechanism behind stress-related hair loss. Ashwagandha doesn't act on the follicle directly, but on the stress attacking it. An indirect approach, but a logical one.
MSM (methylsulfonylmethane)
MSM is an organic sulphur donor. Sulphur is a structural component of keratin (disulphide bridges). A handful of low-quality studies suggest a benefit for hair growth and thickness, but the data is far too limited to draw conclusions.
[Image: Comparison table — supplement, effective dose, level of evidence, average price]
The combined approach: inside + outside
Supplements work from the inside. But the hair follicle is also reachable from the outside, through the scalp. The most complete strategy combines both approaches.
Why a topical approach completes your supplements
A supplement takes 3 to 6 months to show a visible effect — the time it takes for nutrients to reach the follicle through the bloodstream and for a new hair cycle to start. A topical treatment acts directly on the scalp, with a potentially shorter time to results.
Some actives are even more effective applied locally than swallowed. That's the case for rosemary (a 2015 study by Panahi et al. showed efficacy comparable to 2% Minoxidil when applied topically), Redensyl (a patented active targeting follicular stem cells) and Aminexil (which counters perifollicular fibrosis).
Inside/outside synergy
In practice, the most pragmatic combination looks like this:
- Inside: a supplement containing iron (if a deficiency is documented), zinc 15 mg, vitamin D3 2,000 IU
- Outside: a hair serum concentrated in validated actives, applied directly to the scalp
The ORVOVA Roll-On Hair Growth Serum combines 3% rosemary, 2% Redensyl, 2% Aminexil and 2% Anagain in a topical roll-on — four actives targeting complementary hair loss mechanisms. The roll-on applicator massages the scalp as you apply, stimulating local microcirculation.
This dual approach (targeted supplements + topical serum) is what most trichologists recommend to maximise your chances of results.
How to choose a hair supplement: the checklist
The objective criteria
- The real dose of active compounds — not the amount of extract, but the amount of active molecule. A supplement stating "500 mg of zinc extract" tells you nothing; "15 mg elemental zinc (bisglycinate)" tells you everything.
- The form of the actives — bisglycinate > picolinate > citrate > oxide for minerals. Methylfolate > folic acid for B9. Methylcobalamin > cyanocobalamin for B12.
- Formula transparency — run from "proprietary blends" that hide individual doses.
- Certifications — recognised quality marks, GMP manufacturing, third-party lab testing.
- No "fairy dusting" — a good supplement contains 4-6 actives at effective doses. A bad one contains 20 at homeopathic doses.
The warning signs
- Promises of results in "2 weeks" (the hair cycle takes 3-6 months minimum)
- Before/after shots that look too spectacular (often taken under different lighting conditions)
- No precise doses on the label
- Mega-doses of biotin (5,000+ mcg) as the main selling point
- Prices above 40 euros a month with no ingredient quality to justify it
To round off your reading, discover Redensyl: reviews and results.
The blood test to run before any supplementation
This is the most important point in this article: never supplement blind. A basic hair-related blood panel costs between 30 and 80 euros (partly reimbursable in many countries) and saves you from wasting months and hundreds of euros on useless supplements.
The minimum panel
- Ferritin (target > 40 ng/mL, ideally 70)
- 25-OH vitamin D (target 40-60 ng/mL)
- TSH + free T4 (thyroid, a frequent cause of hair loss)
- Serum zinc (target > 80 mcg/dL)
- Full blood count (anaemia, inflammation)
The extended panel (for heavy or persistent hair loss)
- Hormones: oestradiol, free testosterone, DHEA-S, progesterone
- Salivary cortisol (chronic stress)
- Fasting insulin (insulin resistance, linked to androgenetic alopecia)
- CRP (systemic inflammation)
[Image: Annotated hair blood panel — normal values vs optimal values for hair]
The verdict: pragmatism over marketing
Hair supplements are neither miracles nor scams. They're tools — effective when they target a real deficiency, useless when they sprinkle trendy ingredients onto already solid nutritional ground.
The pragmatic strategy:
- Get a blood test
- Correct documented deficiencies with bioavailable forms at effective doses
- Add a targeted topical treatment to act directly on the follicle
- Give yourself 4 to 6 months of consistent follow-up before judging the results
And save the money you'd spend on overdosed biotin — it'll do more good elsewhere.
For further reading, see our article on hair loss and menopause.
Frequently asked questions
How long do you need to take a hair supplement before seeing results?
Three months minimum, ideally six. The full hair cycle lasts 2 to 7 years, and a hair entering its growth phase today won't be visible for several weeks. Most clinical studies assess results at 6 months. The first signs (less shedding, new baby hairs appearing) generally show up between 8 and 12 weeks.
Can you take several hair supplements at the same time?
It's rarely necessary and potentially risky. Stacking two "hair" supplements often creates biotin and zinc overdoses, plus imbalances between minerals. Better to choose one complete supplement, or to supplement specifically for the deficiencies your blood test identified.
Is biotin really useless?
Not useless — useless in people who aren't deficient, which is the vast majority of the population. If your blood test shows a biotin deficiency (rare), supplementation works. Otherwise, mega-doses bring no extra benefit. Biotin at a dose far exceeding your needs doesn't "boost" keratin production — your body simply excretes the excess in your urine.
Can supplements replace a topical treatment?
No, they work on different mechanisms. Supplements correct the nutritional deficiencies limiting growth. Topical treatments act directly on the follicle by stimulating stem cells, inhibiting perifollicular fibrosis or blocking DHT locally. Ideally you combine the two to maximise results.
Do hair supplements make body hair grow too?
No. Unlike oral Minoxidil (which is a medicine, not a supplement), hair supplements don't change body hair. They supply nutrients the body uses across all its functions — hair benefits, but not in a selectively hypertrichotic way.
I'm vegetarian/vegan: which supplements should I choose?
The most common deficiencies in vegans are iron (no haem form available), zinc (bioavailability reduced by phytates in grains), vitamin B12 (absent from plants) and vitamin D (dietary sources are essentially animal). Go for iron bisglycinate (plant-based and well absorbed), zinc picolinate, B12 methylcobalamin and lichen-derived D3 (the only plant source of D3). A blood test matters even more for vegans.
