Hair growth supplements, graded by the evidence
No hair supplement we checked reaches our top grade. Two branded formulas have small trials their makers paid for, most single ingredients rest on one study or none, and iron only matters if a blood test says you are low. Here is every grade, how we award it, and what each rests on.
On this page
The short answer: hair growth supplements have weaker evidence than their marketing suggests. On our five-step scale, nothing we graded earns "Good"; Nutrafol and Viviscal earn "Some" on the strength of small trials their makers paid for; biotin, saw palmetto, tocotrienols, pumpkin seed oil and vitamin D earn "Weak"; iron earns "Test first". This page is information only, written from published sources on 22 September 2026 and not reviewed by a clinician.
A supplement cannot tell you why your hair is thinning. Pattern hair loss, shedding after illness or childbirth, thyroid disease and nutrient deficiencies can all look similar, and the American Academy of Dermatology lists thyroid problems and too little iron, biotin, protein or zinc among the causes of hair loss. A doctor or dermatologist can sort one from another; that visit pays us nothing.
How the grades work
The direct answer: each grade describes the best evidence we could find in PubMed and in government fact sheets, not how popular a product is or whether it pays us.
- Good: consistent randomised, placebo-controlled trials in people with thinning hair, including at least one run independently of the seller. Nothing on this page reaches it.
- Some: two or more randomised, placebo-controlled trials in people with thinning hair, but small, short, or run or paid for by the seller, with no independent repeat that we could find.
- Weak: a single small trial, open-label comparisons, case reports, a government summary calling the evidence too limited, or benefit shown only in people with a deficiency.
- Test first: worth discussing only once a blood test shows you are low.
- Untested: no trial of the ingredient on its own in people with hair loss that we could find.
| Ingredient or product | Grade | What the evidence is | Main caution |
|---|---|---|---|
| Nutrafol (whole formula) | Some | Three placebo-controlled trials, two in women and one in men, all small; none we found was run independently of the company | Many active ingredients at once; the maker asks people on blood thinners to see a physician first |
| Viviscal (marine protein formula) | Some | Placebo-controlled trials in women (2015) and men (2016); the women's trial was funded by the product's maker | Contains shellfish (oyster extract) and iron |
| Biotin | Weak | A 2017 review found 18 reported cases, all in people with an underlying condition | Can distort blood tests, including the troponin test for heart attacks |
| Saw palmetto | Weak | The NIH's complementary-health centre calls the evidence too limited to allow conclusions | May be unsafe in pregnancy or while breastfeeding |
| Tocotrienols | Weak | One placebo-controlled trial of 38 volunteers, from 2010 | One study is too few to rely on |
| Pumpkin seed oil | Weak | One placebo-controlled trial of 76 men, from 2014 | Evidence rests on one small study |
| Vitamin D | Weak | Rated low-quality evidence in a 2023 JAMA Dermatology review | Easy to overdo when a blend is stacked on a separate vitamin D pill |
| Iron | Test first | Useful only when a blood test confirms deficiency | Low iron in men or after menopause needs its cause investigated |
| Ashwagandha, curcumin, marine collagen on their own | Untested | No trial of each alone in people with hair loss that we found | Turmeric and ashwagandha appear in liver-injury grading schemes |
The board: every ingredient, pinned under its grade
Good0
Nothing here yet.
Some2
- Nutrafol (whole formula)
- Viviscal (marine protein formula)
Weak5
- Biotin
- Saw palmetto
- Tocotrienols
- Pumpkin seed oil
- Vitamin D
Test first1
- Iron
Untested1
- Ashwagandha, curcumin, marine collagen on their own
The two branded formulas
The direct answer: Nutrafol and Viviscal are the two names with placebo-controlled trials behind them, which is why they share the "Some" grade, and in both cases the trials we could check were paid for by, or written with, the company selling the product.
Nutrafol's men's formula was tested in a six-month trial that enrolled 112 men and saw 85 finish; the trial was funded by Nutraceutical Wellness Inc., the company behind the brand. Two women's trials of its formulas randomised 40 and 70 women. Our full Nutrafol review walks through each study and scores the men's capsule 5 out of 10 on our published rubric.
Viviscal's 2015 trial in women randomised 60 people for three months and was funded by Lifes2good, the company the paper names as the product's maker; a separate 2016 trial tested its men's formula for six months. Its women's label lists iron and a marine complex made from collagen and oyster extract, so anyone with a shellfish allergy should stop at the label. Our Viviscal vs Nutrafol comparison sets the two side by side.
Single ingredients
The direct answer: single-ingredient supplements mostly rest on one small study, on case reports, or on benefit that only appears when someone was deficient to begin with.
Biotin
Biotin is the ingredient with the loudest reputation and the thinnest evidence. A 2017 review in Skin Appendage Disorders found 18 reported cases of biotin use for hair and nail changes, and in every one the person had an underlying condition; the authors concluded there was not enough evidence for supplementation in healthy people. The FDA has also warned that biotin can make some lab tests read wrongly. Read biotin: when it helps, and the lab-test warning.
Saw palmetto
Saw palmetto is sold as a natural answer to DHT, the hormone behind male pattern hair loss. The NIH's National Center for Complementary and Integrative Health says a few small studies have tested it for male-pattern hair loss and the evidence is too limited to allow conclusions. An open-label 2012 study compared it with finasteride in 100 men over two years; more of the finasteride group improved. The details are in saw palmetto vs finasteride.
Tocotrienols and pumpkin seed oil
Both have one small placebo-controlled trial each: 38 volunteers for tocotrienols in 2010 and 76 men for pumpkin seed oil in 2014. One trial is a starting point for research, not a basis for a monthly habit.
Iron and vitamin D
A 2006 review in the Journal of the American Academy of Dermatology found that studies disagree on whether iron deficiency drives hair loss and said the evidence was not strong enough to recommend screening everyone with hair loss; it also stressed that iron deficiency in men and post-menopausal women needs its cause found. Vitamin D was rated low-quality evidence in the 2023 JAMA Dermatology review. See iron, ferritin and vitamin D: get tested first.
What the big reviews say
The direct answer: independent reviewers see a possible role for some supplements, and they all ask for bigger, independent trials.
A 2023 systematic review in JAMA Dermatology looked at 30 studies of nutritional supplements in people without a known deficiency. It found the highest-quality evidence pointed to a potential benefit for several products, including Viviscal and Nutrafol, rated adverse effects as rare and mild, and asked for larger trials against active comparators. A 2026 meta-analysis of commercial oral supplements, covering 14 studies and 967 participants, called the results promising and said more rigorous, independent research is needed.
Where the honest money goes
A supplement is an optional extra, and a blood test, a doctor's diagnosis and an over-the-counter medicine such as topical minoxidil often come first; none of those pays this site anything. If you decide a branded formula is worth trying, our Nutrafol review lists every current plan price, and our guide to how supplements are (not) regulated explains what a label can and cannot promise.