Hair loss in women is surprisingly common. About one-third of women experience it at some point, and among postmenopausal women, as many as two-thirds deal with thinning hair or bald spots. Losing 50 to 100 hairs a day is normal, but when shedding consistently exceeds that range, something deeper is usually going on. The causes range from hormonal shifts and nutritional gaps to autoimmune conditions and even the way you style your hair.
Female Pattern Hair Loss
The single most common cause of hair loss in women is androgenetic alopecia, also called female pattern hair loss. It’s driven by androgens, a group of hormones that includes testosterone. In women who are genetically predisposed, these hormones shorten the active growth phase of each hair and lengthen the resting gap between when a hair falls out and a new one starts growing. Over time, the follicle itself shrinks and produces a thinner, shorter strand. This process, called follicular miniaturization, is why hair gradually looks less dense rather than falling out in clumps.
Unlike male pattern baldness, which typically creates a receding hairline, female pattern hair loss usually shows up as a widening part or overall thinning across the top of the scalp. It tends to worsen after menopause, when estrogen levels drop and the relative influence of androgens increases. Genetics play a major role: if your mother or grandmother had thinning hair, your risk is higher.
Telogen Effluvium: Stress-Related Shedding
If you’ve noticed handfuls of hair coming out in the shower or collecting on your pillow, you may be dealing with telogen effluvium. This is a temporary but dramatic form of shedding that happens when a large number of hairs shift into their resting phase all at once, then fall out together. The tricky part is timing: the shedding typically starts two to three months after the triggering event, so it can be hard to connect cause and effect.
Common triggers include high fever, severe infection, major surgery, significant psychological stress, crash diets low in protein, thyroid disorders, and stopping birth control pills. Certain medications can also trigger it. The good news is that once the underlying cause is addressed, hair usually recovers within six to eight months without any specific treatment.
Hormonal Changes and PCOS
Hormones are involved in nearly every type of female hair loss, but certain conditions create particularly disruptive imbalances. Polycystic ovary syndrome (PCOS) is one of the most common. PCOS is characterized by excess androgens, which can cause thinning on the scalp while simultaneously increasing hair growth on the face and body. What makes PCOS tricky to identify through blood work alone is that 20 to 40 percent of women with the condition have testosterone levels that fall within the normal reference range, yet they still show clinical signs of androgen excess like acne, unwanted facial hair, and scalp thinning.
Low estrogen and low progesterone can also contribute to hair loss outside of PCOS. These shifts happen naturally during perimenopause and menopause, but they can also occur with certain medical conditions or after discontinuing hormonal contraception.
Postpartum Hair Loss
Many new mothers are alarmed when their hair starts falling out around three months after giving birth. During pregnancy, elevated estrogen extends the hair growth cycle, which is why pregnant women often enjoy thicker, fuller hair. After delivery, hormone levels return to normal, and all the hair that was held in its growth phase enters the shedding phase at once. It can look dramatic, but it’s temporary. Most women see their hair return to its pre-pregnancy thickness within several months.
Thyroid Problems
Both an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism) can disrupt hair growth. Thyroid hormones help regulate the hair cycle, and when production is too high or too low, a larger percentage of hairs enter the resting phase prematurely and eventually fall out. The pattern is usually diffuse thinning across the entire scalp rather than distinct bald patches, so you may notice a general decrease in volume rather than bare spots.
One distinguishing feature of thyroid-related hair loss is that it doesn’t stop at the scalp. You might also notice thinning in your eyebrows, particularly the outer third, and reduced body hair. If your hair loss comes with fatigue, unexplained weight changes, or feeling unusually cold or warm, a thyroid issue is worth investigating.
Iron and Nutritional Deficiencies
Iron deficiency is one of the most overlooked causes of hair loss in women, partly because standard blood work doesn’t always catch it. Most doctors screen using ferritin, a protein that reflects how much iron your body has stored. Hair specialists often consider supplementation when ferritin drops below 70 ng/mL, even if other iron markers look normal. Women with heavy periods are especially vulnerable to low ferritin levels.
Vitamin D deficiency and zinc deficiency have also been linked to hair shedding. Restrictive diets, whether for weight loss or due to eating disorders, can deprive follicles of the protein and micronutrients they need. Hair is a low priority for the body compared to vital organs, so when nutrients are scarce, hair growth is one of the first things to slow down.
Alopecia Areata
Alopecia areata is an autoimmune condition where the immune system mistakenly attacks hair follicles, causing inflammation that shuts down growth. It looks very different from other types of hair loss: it typically produces sudden, round or oval smooth patches on the scalp. The skin in those patches usually looks normal, with no rash, redness, or scarring. Around the edges, you might notice short broken hairs that are narrower at the base than the tip, sometimes called exclamation point hairs.
Some people feel tingling, burning, or itching in a spot just before the hair falls out. Nail changes like tiny pits or dents can also accompany the condition, especially in more extensive cases. Alopecia areata can affect eyebrows, eyelashes, and body hair as well. It’s unpredictable: hair may regrow on its own, or the condition may recur in the same or different areas.
Traction Alopecia From Styling
Hairstyles that pull tightly on the hair can cause a specific type of loss called traction alopecia. Cornrows, tight braids, locs, slicked-back ponytails, tight buns, and hair extensions or weaves (especially on chemically relaxed hair) are common culprits. Even regularly wearing rollers to bed or constantly covering the hair with tightly fitted hats or scarves can contribute.
Early warning signs include pain or stinging on the scalp, crusting, broken hairs around the forehead, and small patches of thinning where the tension is greatest. If caught early and the pulling stops, the hair can recover. But if the tension continues long enough, the follicles scar over and the loss becomes permanent. Where hair once grew, you’ll see smooth, shiny skin that can no longer produce new strands.
How Hair Loss Gets Diagnosed
Because so many different conditions cause hair loss in women, a doctor will typically start with a detailed history: when the shedding started, what the pattern looks like, recent life events, medications, diet, and family history. A physical exam of the scalp helps distinguish between diffuse thinning, patchy loss, and signs of scarring.
Blood tests are often the next step. The most commonly ordered panels check ferritin levels to assess iron stores, thyroid-stimulating hormone (TSH) to screen for thyroid disease, and androgen levels to look for hormonal excess. Depending on the suspected cause, your doctor may also check vitamin D, zinc, or markers for autoimmune conditions. In some cases, a small scalp biopsy helps distinguish between overlapping types of hair loss that look similar on the surface.
Identifying the specific cause matters because treatment depends entirely on what’s driving the loss. Correcting an iron deficiency, managing a thyroid condition, or simply changing a hairstyle can stop the shedding and allow regrowth. The sooner the cause is identified, the better the chances of recovery, particularly for conditions like traction alopecia where delayed treatment can lead to permanent damage.