Hair loss: causes, remedies, and when to worry

Losing 50 to 100 hairs a day is normal: it is part of the hair's natural cycle of continual renewal. Heavier shedding that starts about three months after stress, a high fever, childbirth or a drastic diet is often temporary telogen effluvium and usually resolves on its own within a few months. If, instead, your hair gradually thins, falls out in patches or continues to shed for more than six months, seek advice from a dermatologist.

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

Reading time: 12 minutes

Last updated: October 2026

Scientific review: GP Nutraceuticals Team

Main sources: American Academy of Dermatology, systematic reviews of 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 follicle cells that divide very rapidly, which is why it is quickly affected by nutritional deficiencies, hormonal imbalances, illness and stress. For the same reason, nails can also become weak: learn more in our guide to brittle nails.

Most hair loss, however, has specific causes that need to be identified: telogen effluvium 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 just a shot in the dark.

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 each day is normal.
• Hair loss after stress, fever, childbirth or drastic 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 require a dermatologist.
• Androgenetic alopecia is the most common cause of hair loss 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.

Support from your diet. Biotin, zinc and selenium contribute to the maintenance of normal hair. You can find them in RevePil Forte®, along with keratin, collagen and Annurca apple extract, in one sachet a day. Discover RevePil Forte →

What you'll find in this guide

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

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

This guide is intended solely for informational and educational purposes and is not a substitute for advice from a doctor or other qualified healthcare professional.

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

That is why some daily hair loss is normal: these are hairs that have reached the end of the telogen phase. A problem arises when many follicles enter this phase at the same time, 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. Distinguishing between them is important 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. 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 its 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 hairs in the resting phase peaks in summer, with a smaller second 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 due to 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 starts with a receding hairline and thinning on the crown; in women, with a widening of the central part, often after menopause.

Androgenetic alopecia does not resolve on its own. However, effective treatments are available, such as minoxidil and, for men, finasteride. These should be discussed with a dermatologist: the earlier treatment starts, 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 disease, 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 deficiencies with 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 breakage.

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

Hair loss that lasts more than six months, progressive thinning, or the appearance of bald patches are the main reasons to book an appointment. A dermatologist, who also specializes in hair, can identify the cause and recommend the right treatment.

When to book an appointment

• Heavy hair loss continues for more than 6 months.
• The hair gradually thins on the crown or along the part.
• Bald patches appear.
• The scalp is itchy, burning, red, or flaky.
• The hair breaks off instead of falling out from the root.

How is it diagnosed?

In addition to a consultation and physical examination, the dermatologist may perform a pull test, gently tugging on the hair to assess how many strands come out, and trichoscopy, an examination of the scalp under magnification. Blood tests can help identify a treatable cause of hair loss: a complete blood count and ferritin to assess iron levels, TSH to check the thyroid, vitamin D, and other hormone tests if needed.

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

Hair loss remedies: diet and lifestyle

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

What to put on your plate

• Protein at every meal: fish, eggs, dairy products, legumes, white meat. Keratin is a protein, and insufficient intake soon affects the hair.
• Iron: meat, fish, legumes and leafy green vegetables; pair plant foods with a source of vitamin C for better absorption.
• Zinc: shellfish, 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 who wants 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 the use of straighteners, very hot hair dryers, bleaching and chemical straightening: hair can be damaged to the point of breaking.
• Wash your hair as needed, even every day: washing does not cause healthy hair to fall out; it simply removes hairs that are already in the shedding phase.

Stress and sleep

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

Supplements for hair loss: what do the studies say?

Supplements work best when they address 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 authorized health 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 positive 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 case 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 has been 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 who lose their hair, but controlled studies on supplementation are lacking	Very low
Biotin	Variable doses	No evidence of efficacy 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 to 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 hairs in the growth phase rose from 72.5% to 80.5% over six months, with no significant changes in hair count or density. The effect cannot be attributed to a single 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 is not better

Some substances harm hair when taken in excess: high doses of vitamin A and selenium are known causes of hair loss. People taking several supplements at once should check their total intake and not exceed the recommended doses.

High doses of biotin may also interfere with some laboratory tests, such as troponin tests used to diagnose heart attacks and some hormone tests, as the US Food and Drug Administration has reported. Before having a blood test, 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 claims concern hair loss or regrowth: a supplement cannot claim to stop hair loss. However, Regulation (EU) 432/2012 permits 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 hair claims for keratin, collagen, cystine, or methionine.

Among GP Nutraceuticals supplements, RevePil Forte® contains biotin, zinc, selenium and copper, with these claims, as well as keratin, collagen, L-cystine, and Annurca apple and millet extracts. The full product details are further down, in the section on the nutraceutical approach.

Frequently asked questions about hair loss

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

How many hairs is it normal to lose per day?

Losing 50 to 100 hairs a day is normal. You may see more on days when you wash your hair because washing releases all at once the hairs that were already ready to fall out.

Is hair loss in autumn normal?

Yes, it is a documented phenomenon. In summer, the proportion of hairs in the resting phase increases, and they fall out 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's very common. During pregnancy, many hairs stay in the growth phase; after childbirth, they stop growing and fall out all at once. According to the American Academy of Dermatology, hair loss starts 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 doesn't pull out healthy hair; it only removes hairs that fall out because they've already reached the end of their cycle. Washing your hair less often only lets the hair loss build up, making it more noticeable at the next wash.

Does biotin help 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 interfere with some blood tests.

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

At least three months, because hair grows about 1 cm per 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's 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 progressively thins or falls out in patches, or when the scalp is red, itchy, or painful. In these cases, it's best to see a dermatologist.

Effective remedies and treatments: how to stop hair loss?

It depends on the cause. Telogen effluvium usually resolves on its own once the triggering event has passed, and hair grows back normally within a few months. There are medications proven to be effective for androgenetic alopecia, such as minoxidil and, for men, finasteride, which should be used under a dermatologist's guidance. Supplements are mainly useful when there is a vitamin or mineral deficiency; be wary of anyone who promises to stop hair loss in a few weeks or offers 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 stabilized 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 partially restore density, especially if started early, but regrowth is unlikely in areas that have been bald for many years.

Why do short hairs 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 is advisable to speak to a dermatologist.

In summary

Losing a certain number of hairs every day is a physiological phenomenon, and seasonal hair loss or hair loss after stress is usually temporary. However, progressive hair thinning, patches, or hair loss lasting more than six months requires 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 particularly 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 types of hair loss that require them. However, it can complement a balanced diet with nutrients that contribute to the maintenance of normal hair.

RevePil Forte® is a dietary 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 Annurca apple and millet extracts. 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 the product during pregnancy or while breastfeeding without consulting your doctor first. As with any supplement containing biotin, it is advisable to report its use before having blood tests.

Scientific sources and references

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

Institutional 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

Hair 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 oral supplementation with a natural keratin hydrolysate (Kera-Diet) on hair and nails: randomized, placebo- and benchmark-controlled clinical trial in 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 C, 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 1.1 – October 2026

Added a box on nutrients with authorized hair claims and a link to the guide on brittle nails.

Version 1.0 – October 2026

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