Hair loss: causes, remedies, and when to worry

Losing 50 to 100 hairs a day is normal: it's part of the natural hair cycle, which is constantly renewing itself. Heavier shedding that occurs about three months after stress, a high fever, childbirth, or extreme dieting is often temporary and usually resolves on its own within a few months. If, on the other hand, your hair gradually thins, falls out in patches, or shedding lasts more than six months, you should seek a dermatologist's advice.

In this guide, we explain how hair grows, why it falls out, when to see a dermatologist, and what studies say about nutrition and supplements.

Reading time: 12 minutes

Last updated: October 2026

Scientific review: GP Nutraceuticals Team

Main sources: American Academy of Dermatology, systematic reviews on hair supplements (JAMA Dermatology 2023), and peer-reviewed literature

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Hair loss: a brief overview

Nails and hair are made mainly of keratin, a protein rich in sulfur-containing amino acids such as cysteine. Hair grows thanks to cells in the follicle that divide very rapidly, which is why hair is quickly affected by nutritional deficiencies, hormonal imbalances, illness, and stress.

Most hair loss has specific causes that need to be identified: shedding after a stressful event, iron deficiency, a thyroid disorder, or a genetic predisposition. Supplements can help mainly when they correct a deficiency; without a diagnosis, they risk being little more than guesswork.

Key points

The guide's central message in six points: some hair loss is normal, the causes need to be identified, and supplements are mainly useful for correcting deficiencies.

• Losing a few dozen hairs a day is normal.
• Hair loss after stress, fever, childbirth, or extreme dieting appears about three months later and usually resolves on its own.
• Progressive thinning, patches of hair loss, or shedding lasting more than six months warrant a visit to a dermatologist.
• Androgenetic alopecia is the most common cause of baldness and has effective treatments.
• Iron, zinc, and vitamin D levels should be checked with blood tests before taking supplements.
• Supplements take at least three months to show results for hair.

What you'll find in this guide

The guide starts with how hair grows, moves on to types and causes of hair loss, and ends with nutrition, supplements, and answers to frequently asked questions.

• How hair grows.
• Why hair falls out.
• When to see a dermatologist.
• Nutrition and lifestyle.
• What studies say about supplements.
• Frequently asked questions.

This guide is for informational and educational purposes only and does not replace the advice of a doctor or other qualified healthcare professionals.

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How does hair grow? The hair life cycle

Hair grows from the hair follicle, a small "factory" of cells that produces keratin. Unlike nails, which grow continuously, hair growth follows a cycle of growth and rest.

The three phases of the life cycle

There are about 100,000 follicles on the scalp, and each goes through three phases independently of the others:

1. Anagen (growth): lasts 2 to 6 years and affects 85-90% of hair. During this phase, hair grows about 1 cm per month.
2. Catagen (transition): lasts 2-3 weeks, during which the hair bulb retracts and growth stops.
3. Telogen (resting): lasts about 3 months and affects 10-15% of hair. At the end, the hair falls out and is replaced by a new one.

That is why some daily hair loss is normal: it is hair that has reached the end of the telogen phase. The problem arises when many follicles enter this phase at once, or when the hair that grows back is thinner with each cycle.

Why does hair fall out? Causes of hair loss

Hair loss can be temporary or progressive, and the two most common causes are telogen effluvium, which is temporary, and androgenetic alopecia, which is progressive. It is important to distinguish between them because they follow different courses and require different treatments.

Seasonal hair loss and telogen effluvium

Telogen effluvium is sudden, diffuse hair loss that appears about three months after a triggering event. The most common causes include:

• childbirth (postpartum hair loss);
• high fever, serious infections, surgery;
• crash diets and rapid weight loss;
• severe physical or emotional stress;
• certain medications and stopping birth control pills;
• iron deficiency and thyroid disorders.

In the acute form, hair loss resolves within 3-6 months and hair density is fully restored. It is considered chronic when it lasts for more than six months.

Seasonal hair loss is also a real phenomenon. A Swiss study of more than 800 women found that the proportion of hair in the resting phase peaks in summer, with a second, smaller peak in spring. Since hair falls out about three months after entering this phase, hair loss is most noticeable in autumn.

Androgenetic alopecia and baldness: can they be stopped?

It is by far the most common form of hair loss and affects both men and women. It is caused by a genetic predisposition and the sensitivity of hair follicles to androgen hormones: with each cycle, the hair tends to grow back shorter and thinner. In men, it usually begins with a receding hairline and thinning on the crown, while in women it causes a widening of the central part, often after menopause.

Androgenetic alopecia does not go away on its own. However, effective treatments are available, such as minoxidil and, for men, finasteride, which should be discussed with a dermatologist: the earlier treatment begins, the more hair can be preserved.

Other causes of hair loss: deficiencies, thyroid disorders, and harsh treatments

• Alopecia areata: round bald patches. It is an autoimmune condition that always requires a dermatological assessment and, in more extensive cases, can lead to the loss of all hair.
• Nutritional deficiencies: especially iron, but also protein and zinc in very restrictive diets.
• Thyroid disorders: both hypothyroidism and hyperthyroidism can cause diffuse hair loss.
• Excess of certain substances: paradoxically, too much vitamin A or selenium can also cause hair loss.
• Traction and harsh treatments: very tight hairstyles, bleaching, and repeated straightening can damage the hair shaft, causing hair loss through breakage.

Hair loss: when should you worry and when should you see a dermatologist?

Hair loss lasting more than six months, progressive thinning, or the appearance of patches are the main reasons to seek an appointment. A dermatologist, who is also a hair specialist, can identify the cause and recommend the right treatment.

When to book an appointment

• Heavy hair loss continues after 6 months.
• The hair gradually thins on the crown or along the part.
• Bald patches appear.
• The scalp itches, burns, becomes red, or flakes.
• The hair breaks instead of falling out from the root.

How the diagnosis is made

In addition to taking your history and conducting a physical examination, the dermatologist may perform a pull test, gently tugging on the hair to assess how many strands come out, and trichoscopy, a magnified examination of the scalp. Blood tests can help look for a correctable cause of hair loss: a complete blood count and ferritin to check iron levels, TSH to check thyroid function, vitamin D, and, if needed, other hormone tests.

These tests should be done before starting biotin supplements, or after stopping them for a few days before the blood test: high doses of biotin can skew some lab results, including certain hormone tests.

Remedies for hair loss: diet and lifestyle

A balanced diet is the foundation of healthy hair: follicles need protein, iron, zinc, and vitamins to produce keratin. The most significant deficiencies usually result from very restrictive diets, rapid weight loss, or heavy menstrual periods.

What to put on your plate

• Protein at every meal: fish, eggs, dairy, legumes, and white meat. Keratin is a protein, and an insufficient intake quickly shows in your hair.
• Iron: meat, fish, legumes, and leafy green vegetables; pair plant foods with a source of vitamin C to improve absorption.
• Zinc: seafood, meat, pumpkin seeds, whole grains.
• Healthy fats: oily fish, nuts, extra-virgin olive oil.

Crash diets are among the most common causes of excessive hair loss: anyone looking to lose weight should do so gradually, without eliminating entire food groups. These simple choices help keep hair healthy over time.

Hair care

• Avoid very tight hairstyles, such as high ponytails and tight braids worn every day.
• Limit flat irons, very hot blow-drying, bleaching, and chemical straightening: hair can be damaged to the point of breaking.
• Wash your hair as needed, even daily: washing does not cause healthy hair to fall out; it only dislodges hairs already in the shedding phase.

Stress and sleep

Periods of intense stress can trigger increased hair loss, which usually eases when the stress passes; if stress persists, hair loss may continue. Regular sleep, physical activity, and relaxation techniques support overall well-being; however, if hair loss is significant, it's best to consult your doctor to rule out other causes.

Hair loss supplements: what do the studies say?

Supplements work best when correcting a deficiency, especially of iron, zinc, or vitamin D. The evidence is weaker for people without deficiencies. A systematic review published in JAMA Dermatology analyzed 30 studies on hair supplements: it found a possible benefit for several formulations, but the studies were small and often funded by manufacturers.

Scientific evidence and regulatory claims are two different things. An approved label claim describes a physiological function recognized by an authority and does not prove that a product stops hair loss or promotes hair regrowth. Likewise, a favorable study alone does not authorize a claim.

What the studies suggest

Nutrient or ingredient	Doses used in studies	What the studies say	Quality of evidence
Iron	Only in cases of deficiency	A meta-analysis of 36 studies involving over 10,000 women found lower ferritin levels in those experiencing hair loss. Supplementation makes sense when a deficiency is confirmed	Moderate for the association, low for supplementation
Zinc	50 mg per day, in cases of deficiency	Lower levels in people with alopecia; benefits observed only in those with a deficiency, in small studies	Low
Vitamin D	Individual doses, in cases of deficiency	Low levels are more common in people experiencing hair loss, but controlled studies on supplementation are lacking	Very low
Biotin	Variable doses	No evidence of effectiveness for hair in people without a deficiency	Very low
Multi-ingredient formulations	Combinations of amino acids, vitamins, minerals, and plant extracts	A 2026 network meta-analysis of 19 studies and 1,658 people with androgenetic alopecia observed increased hair density with several formulations compared with placebo	Low-moderate
Keratin	500-1000 mg per day	Two randomized studies involving 50 and 60 women observed less hair loss and stronger hair compared with placebo	Low
L-cystine and millet, in combination	Formulations with B vitamins	In a study of 30 women with telogen effluvium, the proportion of hair in the growth phase increased from 72.5% to 80.5% over six months, with no significant changes in hair count or density. The effect cannot be attributed to the individual ingredient	Low
Annurca apple extract	Procyanidin-rich extract	An Italian clinical study observed more hair, greater density, and more keratin after two months. Apple extract is among the formulations associated with greater density in the 2026 network meta-analysis	Low

More isn’t better

Some substances are harmful to hair when taken in excess: high doses of vitamin A and selenium are known causes of hair loss. Anyone taking several supplements together should check the total amounts and not exceed the recommended doses.

High doses of biotin can also interfere with some lab tests, such as troponin tests used to diagnose a heart attack and some hormone tests, as the U.S. Food and Drug Administration has warned. Before having blood drawn, it is always a good idea to tell your doctor which supplements you are taking.

What a supplement can claim

In the European Union, no authorized claim relates to hair loss or regrowth: a supplement cannot claim to stop hair loss. However, Regulation (EU) 432/2012 allows specific claims for hair:

• biotin, zinc, and selenium contribute to the maintenance of normal hair;
• copper contributes to normal hair pigmentation.

There are no authorized claims about hair for keratin, collagen, cystine, or methionine.

Frequently asked questions about hair loss

Brief answers to the most common questions, from seasonal hair loss to supplements.

How much hair is it normal to lose per day?

Losing 50 to 100 hairs a day is physiologically normal. More hair seems to fall out on days when you wash it because washing dislodges all the hairs that were already ready to fall out.

Is hair loss in autumn normal?

Yes, this is a documented phenomenon. In summer, the proportion of hair at rest increases, and it falls about three months later, in autumn. Seasonal hair loss is temporary and does not permanently reduce hair density.

Hair loss after childbirth: is it normal?

Yes, it is very common. During pregnancy, many hairs remain in the growth phase; after childbirth, they stop growing and fall out all at once. According to the American Academy of Dermatology, hair loss begins about two months after childbirth, peaks around the fourth month, and the lost hair grows back and returns to normal density within 6-9 months.

Does washing your hair often make it fall out?

No. Washing does not pull out healthy hair; it only removes hairs that are falling out because they have already reached the end of their cycle. Washing hair less often only allows more hair to accumulate, so more is noticed at the next wash.

Does biotin make hair grow?

Only if there is a deficiency, which is rare in people with a varied diet. A review of published studies found no evidence of effectiveness in healthy people. At high doses, biotin can also distort some blood test results.

How long does it take to see results from a hair supplement?

At least three months, because hair grows about 1 cm a month and the resting phase lasts about three months. In clinical studies, effects were usually assessed after 3-6 months.

When is hair loss normal, and when should you be concerned?

It is normal to lose a few dozen hairs a day and to experience more intense hair loss for a few months in autumn or after a stressful event. Hair loss becomes a concern when it lasts more than six months, when hair gradually thins or falls out in patches, or when the scalp is red, itchy, or painful. In these cases, it is best to consult a dermatologist.

Effective remedies and treatments: how can you stop hair loss?

It depends on the cause. Telogen effluvium usually resolves on its own once the triggering event has passed, and hair normally grows back within a few months. There are medications with proven effectiveness for androgenetic alopecia, such as minoxidil and, for men, finasteride, which should be used on a dermatologist's advice. Supplements are mainly helpful when there is a vitamin or mineral deficiency; be wary of anyone promising to stop hair loss in a few weeks or of a miraculous home remedy.

When is hair transplantation considered?

Hair transplantation is a surgical procedure that moves follicles from the nape, an area where hair does not fall out, to thinning areas. It is considered for stable androgenetic alopecia when medical treatments are not enough, and should always be preceded by a specialist consultation.

Can hair grow back after thinning or baldness?

It depends on the cause. After telogen effluvium, hair grows back completely because the follicles remain active. Spontaneous regrowth is also common with alopecia areata. With androgenetic alopecia, however, the follicles produce increasingly thin hairs: treatments can stop thinning and partly restore density, especially if started early, but regrowth is unlikely in areas that have been bald for many years.

Why does short hair fall out?

If many of the hairs that have fallen out are short and thin, this may be a sign of androgenetic alopecia: the follicles produce hairs that remain in the growth phase for only a short time. Broken hairs without the small white bulb at the root, on the other hand, indicate damage to the hair shaft from treatments or traction. In either case, it's best to discuss it with a dermatologist.

In summary

Losing a certain number of hairs each day is a physiological phenomenon, and seasonal hair loss or hair loss after stress is usually temporary. Progressive hair thinning, patches, or hair loss lasting more than six months, however, require seeing a dermatologist, because the most common causes, such as androgenetic alopecia, have effective treatments.

The foundation remains a complete diet rich in protein, iron, and zinc, along with gentle hair care. Supplements are especially useful for correcting a deficiency and should be assessed over a realistic period of at least three months.

The GP Nutraceuticals nutraceutical approach

A supplement does not replace a dermatologist's diagnosis or treatments for conditions that require them. However, it can complement a balanced diet with nutrients that contribute to the maintenance of normal hair.

RevePil Forte® is a food supplement in sachets that combines biotin, zinc, selenium, copper, vitamin C, vitamins B6 and B12, and pantothenic acid with sulfur-containing amino acids (L-cystine and L-methionine), keratin, hydrolyzed collagen, and extracts of Annurca apple and millet. Take one sachet a day for courses of at least three months.

Among the authorized claims for its ingredients:

• Biotin, zinc, and selenium contribute to the maintenance of normal hair;
• Zinc and selenium contribute to the maintenance of normal nails;
• Copper contributes to normal hair pigmentation;
• Vitamin C contributes to normal collagen formation for the normal function of the skin;
• Vitamin B6 contributes to normal cysteine synthesis;
• Zinc, selenium, and vitamin C contribute to the protection of cells from oxidative stress.

Do not take this product during pregnancy or breastfeeding without consulting your doctor first. As with any biotin-containing supplement, you should report taking it before having blood tests.

Sources and scientific references

This guide was prepared based on official sources and peer-reviewed scientific literature available at the time of the update.

Official sources

1. American Academy of Dermatology. Do you have hair loss or hair shedding? aad.org
2. U.S. Food and Drug Administration. Biotin (Vitamin B7): Safety Communication – May Interfere with Lab Tests. 2017. fda.gov

Growth and hair loss

3. Liyanage D, Sinclair R. Telogen effluvium. Cosmetics. 2016;3(2):13. doi:10.3390/cosmetics3020013
4. Kunz M, Seifert B, Trüeb RM. Seasonality of hair shedding in healthy women complaining of hair loss. Dermatology. 2009;219(2):105-110. PMID: 19407435

Nutrients and supplements

5. Drake L, Reyes-Hadsall S, Martinez J, et al. Evaluation of the safety and effectiveness of nutritional supplements for treating hair loss: a systematic review. JAMA Dermatol. 2023;159(1):79-86. PMID: 36449274
6. Zhou L, Zhu W, Chen Y. Effects of dietary supplements on androgenetic alopecia: a systematic review and network meta-analysis. Front Nutr. 2026. PMID: 41561175
7. Almohanna HM, Ahmed AA, Tsatalis JP, Tosti A. The role of vitamins and minerals in hair loss: a review. Dermatol Ther (Heidelb). 2019;9(1):51-70. PMID: 30547302
8. Treister-Goltzman Y, Yarza S, Peleg R. Iron deficiency and nonscarring alopecia in women: systematic review and meta-analysis. Skin Appendage Disord. 2022. PMID: 35415182
9. Park H, Kim CW, Kim SS, Park CW. The therapeutic effect and the changed serum zinc level after zinc supplementation in alopecia areata patients who had a low serum zinc level. Ann Dermatol. 2009. PMID: 20523772
10. Banihashemi M, Nahidi Y, Meibodi NT, et al. Serum vitamin D3 level in patients with female pattern hair loss. Int J Trichology. 2016. PMID: 27625563
11. Patel DP, Swink SM, Castelo-Soccio L. A review of the use of biotin for hair loss. Skin Appendage Disord. 2017;3(3):166-169. PMID: 28879195
12. Beer C, Wood S, Veghte RH. A clinical trial to investigate the effect of Cynatine HNS on hair and nail parameters. ScientificWorldJournal. 2014. PMID: 25386609
13. Nobile V, Tursi F, Cestone E, et al. The effects of the oral supplementation with a natural keratin hydrolysate (Kera-Diet) on hair and nails: randomized, placebo and benchmark-controlled clinical trial on healthy females. Trichol Cosmetol Open J. 2021. doi:10.17140/TCOJ-4-115
14. Lengg N, Heidecker B, Seifert B, Trüeb RM. Dietary supplement increases anagen hair rate in women with telogen effluvium: results of a double-blind, placebo-controlled trial. Therapy. 2007;4(1):59-65. doi:10.2217/14750708.4.1.59
15. Tenore GC, Caruso D, Buonomo G, et al. Annurca apple nutraceutical formulation enhances keratin expression in a human model of skin and promotes hair growth and tropism in a randomized clinical trial. J Med Food. 2018. PMID: 28956697

Regulatory references

16. Commission Regulation (EU) No 432/2012, establishing a list of permitted health claims made on foods. eur-lex.europa.eu

Update history

We update this guide when new guidelines or relevant studies are published.

Version 1.0 – October 2026

First published. Main sources: American Academy of Dermatology, 2023 JAMA Dermatology systematic review on supplements for hair loss, reviews on vitamins and minerals and telogen effluvium, 2026 network meta-analysis on supplements for androgenetic alopecia.