What is the most common cause of hair loss in women?

Female pattern hair loss, a hereditary condition that for most women begins in midlife, in the 40s, 50s or 60s. It shows up as a widening part and a thinner ponytail and tends to progress without treatment.

When should I see a dermatologist about hair loss?

When hair loss comes on quickly, when you cannot tell shedding from thinning, or when you want treatment. The AAD says treatment works best started early and that a board-certified dermatologist can find the cause with questions, a scalp exam and sometimes blood tests or a biopsy.

Hair and skin

What causes hair loss in women?

Q: Is it shedding or hair loss?

Shedding 50 to 100 hairs a day is normal. Excessive shedding, called telogen effluvium, usually follows a stressor by a few months, such as illness, surgery, childbirth, major stress, high fever or stopping birth control pills, and often resolves within six to nine months. Hair loss means something has stopped the hair growing.

Q: Does menopause cause hair loss?

The American Academy of Dermatology says female pattern hair loss most often begins in midlife and lists hormonal imbalance as a cause of thinning, but it does not list menopause itself as a shedding trigger. A dermatologist can tell which type you have.

Q: Can a thyroid problem or low iron cause hair loss?

Dry, thinning hair is a listed symptom of hypothyroidism, which is much more common in women. Iron deficiency anemia causes tiredness and weakness and is more common in women with heavy periods. Both are reasons to ask about testing rather than to self-treat.

Q: Does biotin help hair loss?

A 2017 review found benefit only in 18 case reports where people had an underlying deficiency or condition, and not enough evidence for healthy people. The FDA warns that biotin can interfere with lab tests, including causing falsely low troponin results.

By Anna Winbrown · Published October 18, 2026

The most common cause of hair loss in women is female pattern hair loss, a hereditary condition that for most women begins in the 40s, 50s or 60s and shows up as a widening part and a thinner ponytail. ^[1] Hair in the drain after an illness, a surgery or a hard few months is usually something else: excessive shedding, which often stops on its own. ^[2]

Hairbrush and comb on a coral tray beside a teal towel.

Is it shedding or hair loss?

Dermatologists draw a line between the two. It is normal to shed between 50 and 100 hairs a day; shedding significantly more than that is called telogen effluvium. ^[2] The American Academy of Dermatology lists the common triggers: losing 20 pounds or more, giving birth, a lot of stress such as caring for a sick relative or going through a divorce, a high fever, an operation, recovering from an illness, and stopping birth control pills. ^[2] Most people notice the extra shedding a few months after the event, and within six to nine months the hair tends to regain its normal fullness, unless the stressor continues. ^[2]

Hair loss is different: something stops the hair from growing. The academy's list of common causes is hereditary hair loss, an overreacting immune system, some drugs and treatments, hairstyles that pull, harsh hair-care products, and compulsive pulling. ^[2] A woman who inherits the genes for hereditary hair loss tends to notice gradual thinning rather than a receding hairline. ^[2]

What is female pattern hair loss?

Female pattern hair loss, or FPHL, is the most common cause of hair loss in women, and for most women it begins in midlife, in the 40s, 50s or 60s. ^[1] It is progressive: without treatment it can move from a widening part to overall thinning, although not every woman reaches that stage and women do not lose all their hair the way some men do. ^[1] It is the same condition as male pattern hair loss; the medical term for both is androgenic alopecia, and it is the most common cause of hair loss worldwide. ^[3]

How common is it? The academy gives no number. The best estimate we found is a 2001 British clinic study of 377 women who came in for reasons unrelated to hair: 6% of those under 50 had female pattern hair loss, rising to 38% at 70 and over. ^[5] That is one clinic in one country, so treat it as a rough scale, not a US statistic.

Does menopause cause hair loss?

The honest answer is that the dermatology guidance does not say so directly. The academy ties female pattern hair loss to midlife and to inherited genes, and it lists hormonal imbalance as a cause of thinning, naming polycystic ovary syndrome and stopping some birth control pills as examples. ^[1]^[3] Menopause does not appear on its list of shedding triggers. ^[2] So if your hair is thinning in your late 40s, the likeliest explanation on the evidence is female pattern hair loss arriving on its usual schedule, and a dermatologist can confirm or rule that out.

Can a thyroid problem or low iron cause hair loss?

Both are worth asking about. The National Institute of Diabetes and Digestive and Kidney Diseases lists dry, thinning hair among the common symptoms of hypothyroidism, alongside fatigue, weight gain, trouble tolerating cold, joint and muscle pain, and heavy or irregular periods, and notes that women are much more likely than men to develop it. ^[6] It also warns that many of those symptoms are common and do not necessarily mean a thyroid problem. ^[6]

Iron deficiency is not uncommon in the United States, especially among women under 50, and women with heavy periods are a group at risk. ^[7] The NIH Office of Dietary Supplements lists weakness, tiredness, lack of energy and trouble concentrating as symptoms of iron deficiency anemia; its consumer fact sheet does not list hair loss. ^[7] The practical point: "please check my thyroid and my iron" is a reasonable sentence to bring to an appointment, especially if your periods have become heavier in perimenopause. It is not a reason to start taking iron on your own.

What to bring to the dermatologist

When it started and whether it came on quickly or gradually; the academy says those are the first questions a dermatologist asks. ^[4] Anything that happened two to four months before the shedding began: illness, surgery, a big weight change, a stopped medication. ^[2] A list of every medication and supplement you take, because hair loss is a possible side effect of some medications and you should never stop one without asking the prescriber. ^[3] And a photo of your part from a year or two ago, if you have one.

Does biotin help hair loss?

Biotin is in almost every hair gummy, and the evidence behind it is thin. A 2017 review searched the literature and found 18 reported cases where biotin helped hair or nails; in every one, the person had an underlying condition or deficiency. ^[8] The authors concluded that those cases are uncommon and that there is not sufficient evidence for supplementing in healthy people. ^[8] There is also a safety point most labels leave out: the FDA says biotin, often found in dietary supplements, can significantly interfere with certain lab tests and cause incorrect results that may go undetected, and it continues to receive reports of falsely low troponin results, a test used when a heart attack is suspected. ^[9] If you take biotin, tell your doctor and the lab before any blood test.

What treatments exist for female pattern hair loss?

This is a clinician decision, and the options are prescription. The academy says some prescription medications have proven effective in helping women with female pattern hair loss grow hair and prevent it from worsening; it names spironolactone, a pill it says is effective in about 40% of women with the condition, and it stresses that women must not become pregnant while taking it. ^[1]^[4] It also says the earlier treatment starts, the more likely regrowth is, that results can take months, and that no one treatment works for everyone. ^[4] We do not recommend products; the right question for your appointment is which, if any, of these fits your situation.

When to talk to your clinician

The American Academy of Dermatology's position is that effective treatment begins with finding the cause, and that a board-certified dermatologist gets there by asking how long you have had hair loss and whether it came on quickly, examining your scalp, nails and other areas with hair, and sometimes ordering blood tests or a scalp biopsy. ^[4] Go sooner rather than later if the loss is rapid, if you see scaly or inflamed areas or what look like small black dots on the scalp, which can signal a scalp infection, or if you suspect a medication. ^[3] And if a video or an article has told you which type you have, be skeptical: the academy says other causes can look like female pattern hair loss, and treatment works best when it is started early on the right diagnosis. ^[4]

Sources

American Academy of Dermatology, Thinning hair and hair loss: could it be female pattern hair loss? Retrieved 2026-10-18.
American Academy of Dermatology, Do you have hair loss or hair shedding? Retrieved 2026-10-18.
American Academy of Dermatology, Hair loss: who gets and causes. Retrieved 2026-10-18.
American Academy of Dermatology, Hair loss: diagnosis and treatment. Retrieved 2026-10-18.
Birch MP, Messenger JF, Messenger AG. Hair density, hair diameter and the prevalence of female pattern hair loss. British Journal of Dermatology, 2001;144(2):297-304. Abstract retrieved 2026-10-18.
National Institute of Diabetes and Digestive and Kidney Diseases, Hypothyroidism (underactive thyroid). Last reviewed March 2021. Retrieved 2026-10-18.
NIH Office of Dietary Supplements, Iron: fact sheet for consumers. Updated August 17, 2023. Retrieved 2026-10-18.
Patel DP, Swink SM, Castelo-Soccio L. A review of the use of biotin for hair loss. Skin Appendage Disorders, 2017;3(3):166-169. Abstract retrieved 2026-10-18.
US Food and Drug Administration, Biotin interference with troponin lab tests. Page dated June 21, 2022. Retrieved 2026-10-18.

Every statement above was checked against the linked page on October 18, 2026. This article is education, not individual medical advice. Related: Signs of perimenopause. Get the free 7-Day Midlife Sleep Reset.