Does vitamin A affect hair growth and hair loss?

We found no trial of vitamin A on its own for hair growth. The strongest evidence near the question is a 2026 meta-analysis of 14 studies in 967 adults taking branded multi-ingredient hair supplements, which lowered telogen hair density by 5.91 against placebo (95% CI 5.08 to 6.74). Those products mix vitamins, minerals and plant extracts, many trials were industry funded, and the authors call the results preliminary, so vitamin A's share is unknown. The firmer link runs the other way. Too much preformed vitamin A, from very high dose supplements or vitamin A drugs, is associated with hair loss.

Unsettled. Whether extra vitamin A helps hair grow has not been tested in a way that can answer it. The only randomized trial that used it, in 1989, combined retinol with L-cystine and gelatin. Its 18,000 IU daily dose of retinol is above the adult upper limit of 10,000 IU for preformed vitamin A.

What the trials found

Hair supplements

The 2026 meta-analysis pooled randomized and open-label trials of products such as Nutrafol, Viviscal, Nourkrin, Lambdapil and Forti5, taken for 12 weeks to 12 months by adults with hair loss or thinning. Besides the fall in telogen density, anagen hair density rose by 10.48 against placebo (95% CI 8.81 to 12.14). Telogen hairs are in the resting phase before they shed, and anagen hairs are growing. These are counts on a magnified patch of scalp, and the review does not say how the change looks in a mirror.

In the 1989 double-blind trial, 47 people with diffuse hair loss took retinol with L-cystine and gelatin, and the share of hairs in the resting phase fell by 13.5 percent from its starting value. It is an old trial read from the abstract alone, and retinol was never tested apart from the other two ingredients.

Too much vitamin A

In a randomized trial of 283 people after surgery for early lung cancer, 300,000 IU of retinol a day for at least a year was compared with observation. Mild hair loss was reported in under 10 percent, and it went away on its own. Dry, peeling skin affected 60 percent. That dose is about 30 times the adult upper limit.

Isotretinoin is a vitamin A drug used for severe acne. Across 22 studies, hair loss was reported in 5.7 percent of patients on 0.5 mg/kg a day or more and 3.2 percent on lower doses. Reporting of hair loss differed between studies, and the review did not test the gap.

Two case reports show what long excess can look like. A woman on long-term kidney dialysis developed gradual hair loss with a blood vitamin A level of 140 micrograms per dL from ordinary multivitamins, against a normal range of 20 to 80. Failing kidneys let vitamin A build up, so her case does not transfer to people with working kidneys. A 51-year-old woman who took 27,500 to 35,000 IU a day for 30 years developed the skin and hair changes of chronic vitamin A toxicity along with extensive liver disease.

Observational data add one signal. A 2026 review of 17 diet and hair studies found a single study linking high retinol intake to more severe alopecia areata. That is an association from one study and says nothing about cause.

Who should be careful

Not for everyone. Women who are or might be pregnant, and women who are breastfeeding, are advised by the NIH not to take more than 3,000 mcg RAE (10,000 IU) of vitamin A from supplements a day, because of the risk of birth defects. Hair supplements are often bought by women of childbearing age, so the vitamin A on the label is worth adding up. Beta-carotene from plants is not known to cause birth defects.

Regular high doses of preformed vitamin A cause chronic toxicity, which the NIH describes as dry skin, painful muscles and joints, fatigue, depression and abnormal liver tests. The adult upper limit of 3,000 mcg RAE counts food and supplements together and rests on liver damage, birth defects and toxicity in children. People on dialysis or with kidney failure can build up vitamin A from ordinary multivitamin doses, as the case above shows.

What expert bodies say

We found no position from an expert body on vitamin A for hair growth or hair loss. The NIH Office of Dietary Supplements sets the upper limits and the pregnancy advice described above, and states that beta-carotene is not known to be toxic to the unborn child in the way preformed vitamin A is.

How we searched

What would change this answer

• A placebo-controlled trial of vitamin A alone at an ordinary dose in people with hair loss, ideally in people with low vitamin A. We found none.
• Hair supplement trials that report each ingredient's dose and test them separately, run independently of the makers.
• Better counts of hair loss at moderate supplement doses. The harm data come from drug doses, a dose 30 times the limit and two case reports.

How much vitamin A you need, and where it comes from in food, is in the vitamin A guide.

Sources

1. ev-vahl-01 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs and open-label trials · n = 967
   Meta-analysis demonstrated significant improvements with oral supplements versus placebo: reduced telogen hair density (mean difference [MD] -5.91, 95% confidence interval [CI] -6.74 to -5.08, p < 0.00001), increased anagen hair density (MD 10.48, 95% CI: 8.81 to 12.14, p < 0.00001), and reduced telogen proportion (MD 3.08, 95% CI: -3.35 to -2.81, p < 0.00001).
   
   Who: adults with alopecia or hair thinning; branded oral supplements (Nutrafol, Viviscal, Nourkrin, Lambdapil, Forti5 and others), 12 weeks to 12 months
   Effect: telogen hair density MD -5.91 (95% CI -6.74 to -5.08); anagen density MD +10.48 (8.81 to 12.14)
   Certainty: products mix vitamins, minerals and botanicals, so the share of vitamin A cannot be separated; many trials industry funded; authors call results preliminary
   J Cosmet Dermatol, 2026 · checked 2026-10-06 · we read the abstract
2. ev-vahl-02 · Randomized controlled trial(s) · double-blind randomized placebo-controlled trial (after a 36-patient pilot) · n = 47
   In the double blind study (II) the trichogram showed a significant decrease of the telogen rate by 13.5% compared with pathological baseline values.
   
   Who: patients with diffuse-type hair loss, daily 18,000 IU retinol plus 70 mg L-cystine plus 7,000 mg gelatin, long-term oral therapy
   Effect: telogen rate -13.5% from baseline; anagen rate +8%; placebo anagen rate fell from 47.7% to 39.9%
   Certainty: old German trial, abstract only; combination product, so retinol alone is not tested; 18,000 IU is above the adult UL of 10,000 IU preformed
   Hautarzt, 1989 · checked 2026-10-06 · we read the abstract
3. ev-vahl-03 · Observational data · systematic review of trials and observational studies, frequency analysis without meta-analysis · n = 3940
   A summary of the available data suggested that patients on <0.5 mg/kg/d of isotretinoin experienced hair loss at a frequency of 3.2% versus those on ≥0.5 mg/kg/d, who experienced hair loss at a frequency of 5.7%.
   
   Who: patients with acne vulgaris on oral isotretinoin, below 0.5 mg/kg/day (n = 565) or at least 0.5 mg/kg/day (n = 3375)
   Effect: hair loss 18/565 (3.2%) at <0.5 mg/kg/d vs 192/3375 (5.7%) at >=0.5 mg/kg/d; no inferential test
   Certainty: isotretinoin is a retinoid drug, not dietary vitamin A; supports the mechanism that excess retinoid activity drives shedding; reporting of hair loss was inconsistent
   JAAD International · checked 2026-10-06 · we read the fulltext
4. ev-vahl-04 · Observational data · systematic review of mostly observational studies · n = 1 study
   Regarding alopecia areata (AA), one study reported that high retinol intake was associated with increased disease severity (Hagino et al., 2021).
   
   Who: 17 studies, 61,332 participants (97% women), ages 7 to 77; the retinol finding comes from one study in alopecia areata
   Effect: high retinol intake associated with greater alopecia areata severity; no effect size reported in the review
   Certainty: single observational study behind the statement; association, not cause
   Nutr Health, 2026 · checked 2026-10-06 · we read the fulltext
5. ev-vahl-05 · Randomized controlled trial(s) · randomized controlled trial, open observation control · n = 283
   Other symptoms such as dyspepsia, headache, nosebleeds and mild hair loss occurred in less than 10% of patients, and were self-terminating.
   
   Who: patients after resection of stage I lung cancer, retinol palmitate 300,000 IU daily for at least 12 months vs observation, median follow-up 28 months
   Effect: skin dryness and desquamation 60%; dyspepsia, headache, nosebleeds and mild hair loss each under 10%, self-limiting; 3% stopped treatment
   Certainty: dose is 30 times the adult UL of preformed vitamin A; exact hair loss rate not given
   Oncology, 1991 · checked 2026-10-06 · we read the abstract
6. ev-vahl-06 · Laboratory or animal data · case report · n = 1
   Her serum vitamin A level was 140 micrograms/dL (a normal level is 20 to 80 micrograms/dL).
   
   Who: one adult woman on long-term renal dialysis taking conventional multivitamins
   Effect: serum vitamin A 140 micrograms/dL (normal 20 to 80) with progressive alopecia
   Certainty: single case; kidney failure causes vitamin A to build up, so this does not apply to people with normal kidneys
   Arch Dermatol, 1979 · checked 2026-10-06 · we read the abstract
7. ev-vahl-07 · Laboratory or animal data · case report · n = 1
   The patient displayed the classic symptoms of the disease, including skin and hair changes, esophageal varices and extensive liver disease.
   
   Who: one 51-year-old woman, 27,500 to 35,000 IU vitamin A daily for 30 years
   Effect: skin and hair changes, esophageal varices, extensive liver disease
   Certainty: single case; dose roughly 3 times the adult UL for decades
   Am J Hosp Pharm, 1978 · checked 2026-10-06 · we read the abstract
8. ev-vahl-08 · Position of an expert body · government fact sheet · n = —
   Chronic hypervitaminosis A (regular consumption of high doses) can cause dry skin, painful muscles and joints, fatigue, depression, and abnormal liver test results [85].
   
   Who: people regularly taking high doses of preformed vitamin A
   Effect: chronic hypervitaminosis A: dry skin, painful muscles and joints, fatigue, depression, abnormal liver tests
   Certainty: ODS does not list hair loss in this sentence; hair loss evidence comes from case reports and retinoid drug data
   NIH Office of Dietary Supplements, Vitamin A and Carotenoids Fact Sheet for Health Professionals · checked 2026-10-06 · we read the section
9. ev-vahl-09 · Position of an expert body · government fact sheet · n = —
   Experts advise women who are or might be pregnant and those who are lactating not to take high doses (more than 3,000 mcg RAE [10,000 IU] daily) of vitamin A supplements [1].
   
   Who: women who are or might be pregnant and lactating women
   Effect: avoid supplemental vitamin A above 3,000 mcg RAE (10,000 IU) a day because of birth defect risk
   Certainty: relevant because hair supplements and retinoids are often used by women of childbearing age
   NIH Office of Dietary Supplements, Vitamin A and Carotenoids Fact Sheet for Health Professionals · checked 2026-10-06 · we read the section
10. ev-vahl-10 · Position of an expert body · government fact sheet · n = —
    Unlike preformed vitamin A, beta-carotene is not known to be teratogenic or lead to reproductive toxicity [1].
    
    Who: general population
    Effect: no teratogenicity known for beta-carotene; long-term excess causes harmless yellow-orange skin
    Certainty: toxicity limits apply to preformed vitamin A only
    NIH Office of Dietary Supplements, Vitamin A and Carotenoids Fact Sheet for Health Professionals · checked 2026-10-06 · we read the section
11. ev-vahl-11 · Position of an expert body · government fact sheet · n = —
    The FNB based these ULs on the amounts associated with an increased risk of liver abnormalities in men and women, teratogenic effects, and several toxic effects in infants and children.
    
    Who: all age groups; adult UL 3,000 mcg RAE of preformed vitamin A
    Effect: UL basis: liver abnormalities, teratogenic effects, toxic effects in infants and children
    Certainty: UL numbers sit in an ODS table; this card cites the text that explains them
    NIH Office of Dietary Supplements, Vitamin A and Carotenoids Fact Sheet for Health Professionals · checked 2026-10-06 · we read the section