Hair Growth Supplements: Biotin, Nutrafol and Collagen Under the Evidence Microscope

Hair supplements are everywhere, from gummies in the checkout aisle to subscription boxes recommended by doctors. Some have real clinical trials behind them. Others mostly have marketing. And one of the most popular, biotin, comes with an FDA safety warning most buyers never see.

Quick answer

  • Biotin: No good evidence it grows hair in people who aren't deficient, and true deficiency is uncommon (2024 review; 2026 systematic review). High doses can skew lab tests, including tests used to diagnose heart attacks (FDA).
  • Nutrafol and some other multi-ingredient supplements have small randomized trials suggesting a possible benefit, but many studies were run or funded by the companies (JAMA Dermatology review).
  • Collagen: Very little evidence specific to hair.
  • Supplements aren't FDA-approved to treat hair loss. A dermatologist can check for causes like iron or thyroid problems first.

Why supplements are hard to judge

In the U.S., dietary supplements don't need FDA approval before they're sold, and their makers don't have to prove they work. Many supplement studies:

  • are small (dozens of people, not thousands),
  • are short (3–6 months),
  • are funded by the manufacturer or have company employees as authors,
  • measure multi-ingredient formulas, so no single ingredient can take the credit, and
  • enroll people with "self-perceived thinning" rather than a confirmed diagnosis.

None of this means a product doesn't work. It means the evidence is weaker than the marketing suggests.

Biotin: popular, but mostly unproven for hair

What the research says

Biotin (vitamin B7) deficiency can cause hair thinning, but it's rare in people who eat a balanced diet. The question is whether extra biotin helps everyone else.

  • A 2017 review in Skin Appendage Disorders found reports of benefit only in people with an underlying deficiency or specific conditions (Karger).
  • A 2024 review in The Journal of Clinical and Aesthetic Dermatology found only three studies that qualified. The best one, a double-blind, placebo-controlled trial, found "no difference between the biotin and placebo groups for hair growth." The authors concluded that biotin's use "is not supported by high-quality studies" (PubMed).
  • A May 2026 systematic review of 10 studies found biotin alone "did not show consistent benefit" on objective hair outcomes. It recommended considering biotin only when deficiency or malabsorption is suspected or confirmed (Dermato).

The American Academy of Dermatology says dermatologists recommend vitamin supplements only if a deficiency is confirmed (AAD).

The FDA warning about lab tests

Many lab tests use a biotin-based chemical reaction. When you have lots of biotin in your blood, those tests can give falsely high or falsely low results.

  • FDA first warned about this in November 2017 and updated the warning on November 5, 2019, saying it continued to receive reports of biotin causing falsely low troponin results. Troponin is a key blood test for diagnosing heart attacks, so a false low could mean a missed diagnosis (Healio coverage).
  • Some hair, skin and nail supplements contain biotin at up to 650 times the recommended daily intake (Healio).
  • FDA's device page (updated June 21, 2022) listed troponin tests that were still vulnerable to biotin interference (FDA).

What to do: Tell your doctor and the lab if you take biotin or any multi-ingredient "hair, skin and nails" product, before blood tests. Many hair supplements contain biotin even when it isn't in the name.

Nutrafol: more data than most, with caveats

The trials

  • 2018, Journal of Drugs in Dermatology: a six-month, randomized, double-blind, placebo-controlled trial in 40 women with self-perceived thinning hair (26 on the supplement, 14 on placebo). The authors reported significant increases in terminal and vellus hair counts at days 90 and 180 compared with placebo. One of the two authors was affiliated with Nutraceutical Wellness Inc., the company behind Nutrafol (JDD).
  • Later company-associated studies looked at perimenopausal and postmenopausal women and a mixed group of men and women of diverse ethnicities (the latter single-blind, not placebo-controlled) (PubMed).

The independent review

A systematic review in JAMA Dermatology (published online November 30, 2022) looked at 30 studies, including 17 randomized trials, in people without known nutritional deficiencies. It found that the supplements with the highest-quality evidence, including Nutrafol, Viviscal (a marine-protein product), Nourkrin, zinc, pumpkin seed oil and several others, showed potential benefit. It said side effects were rare and mild, and recommended shared decision-making between doctors and patients (JAMA Dermatology; MedicalXpress summary).

"Highest-quality evidence" here means compared with the other supplements. The individual trials were still mostly small, short, and often industry-supported.

Ownership and marketing

Unilever acquired a majority stake in Nutrafol in May 2022. Its announcement called Nutrafol the "#1 dermatologist recommended hair growth brand in the U.S." based on an IQVIA survey, and said more than 3,000 physicians sold the products (Unilever). "Most recommended" describes what doctors recommend, not how well the product works.

Marine protein and collagen

  • Marine protein complexes (like Viviscal) were among the supplements with better-quality evidence in the 2022 JAMA Dermatology review, though again with small, often sponsored trials.
  • Collagen: We found very little evidence for collagen peptides alone. One 2023 randomized, assessor-blinded, three-month study tested a supplement combining amino acids, iron, selenium and marine collagen, so collagen's own effect can't be isolated (Skin Research and Technology). Hair is made of keratin, and eating collagen doesn't send collagen straight to your follicles. Your body digests it into amino acids like any other protein.

Where prescription options fit (information, not advice)

Dermatologists have more-studied tools for pattern hair loss. Topical minoxidil is FDA-approved for men and women. Some dermatologists prescribe low-dose oral minoxidil off-label, and oral finasteride and spironolactone are used in certain patients (AAD). Oral minoxidil has become more popular. A 2025 dermatology review reported common effects like unwanted facial and body hair and temporary shedding, rare serious heart-related effects, and conditions where it shouldn't be used, such as pregnancy (American Journal of Clinical Dermatology). These are prescription decisions that need medical supervision. Don't start, combine or adjust these medications on your own.

Checklist before buying a hair supplement

  1. Get checked first. Ask a doctor about iron/ferritin, thyroid, vitamin D and other causes of shedding. Fixing a real deficiency can matter more than any gummy.
  2. Read the label for biotin, and tell your lab and doctor before blood tests.
  3. Check doses of vitamin A, selenium and zinc. Too much of some nutrients can itself cause hair loss or other harm, and stacking several products adds up.
  4. Look for the actual study: How many people? How long? Placebo-controlled? Who funded it?
  5. Be wary of "clinically proven" claims that don't link to published research.
  6. Pregnant, breastfeeding, on blood thinners or other medications? Ask a pharmacist or doctor first. Herbal ingredients can interact with medications.
  7. Give it a defined trial period agreed with your clinician, and stop if nothing changes.
  8. Stylists: you can share observations about hair condition, but refer clients with sudden, patchy or inflamed-scalp hair loss to a dermatologist. Don't recommend supplement doses.

What we don't know yet

  • Whether any hair supplement works in large, independent, long-term trials.
  • Which ingredient in a multi-ingredient formula is doing the work, if any.
  • How results differ across ages, sexes, ethnicities and hair types. Most trials have enrolled small, narrow groups.

FAQ

Does biotin help hair grow? Only if you're deficient, and that's uncommon. Reviews in 2024 and 2026 found no consistent benefit in people without deficiency.

Can biotin affect blood tests? Yes. FDA has warned that high-dose biotin can cause falsely high or low results, including falsely low troponin in heart-attack testing. Tell your doctor and lab.

Is Nutrafol clinically proven? It has small randomized trials suggesting benefit, and an independent review listed it among supplements with the best available evidence. Most studies involved the company, and none are large long-term trials.

Does collagen make hair grow? There's little direct evidence. Studies that include collagen usually combine it with other nutrients.

Are hair supplements safe? Side effects in studies were generally mild, but supplements vary in quality and dose. Excess vitamin A or selenium can be harmful, and biotin interferes with lab tests.

This article is for general information and is not medical advice. Talk with a board-certified dermatologist or your doctor before starting supplements or medication for hair loss.

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