Why Is My Hair
Falling Out?
10 Causes & What to Do
Noticing more hair in the shower drain or on your pillow? You’re not alone — and most causes are treatable. Here’s what science says.
Quick Answer
Hair loss (alopecia) has many triggers — from hormonal shifts and nutritional gaps to stress and genetics. The average person naturally sheds 50–100 hairs per day, but when loss accelerates or patches appear, it’s time to investigate. Most causes respond well to the right treatment once identified.
First: Is Your Hair Loss Actually Normal?
Hair grows in cycles — a growth phase (anagen, 2–7 years), a transitional phase (catagen, ~10 days), and a resting/shedding phase (telogen, ~3 months). Shedding 50–100 hairs daily is completely normal. If you’re seeing significantly more — or bald patches forming — that’s the signal to read on.
What’s Making Your Hair Fall Out
Androgenetic Alopecia (Pattern Hair Loss)
The most common cause of hair loss in both men and women, affecting roughly 50 million men and 30 million women in the U.S. It’s driven by a genetic sensitivity to dihydrotestosterone (DHT), a byproduct of testosterone that shrinks hair follicles over time. In men, it appears as a receding hairline or crown thinning; in women, as a widening part or diffuse thinning at the top of the scalp.
It’s progressive — meaning the earlier you address it, the better your outcomes. Genetics don’t guarantee you’ll lose hair, but they do determine your susceptibility.
- Minoxidil (Rogaine) — FDA-approved topical applied daily; effective for both sexes
- Finasteride (Propecia) — prescription oral DHT-blocker for men
- Spironolactone — prescription option for women with hormonal pattern loss
- Low-level laser therapy (LLLT) devices — clinically supported adjunct
- Hair transplant surgery for advanced cases
Telogen Effluvium (Stress-Related Shedding)
A sudden physical or emotional shock — surgery, illness, childbirth, rapid weight loss, or extreme stress — can push large numbers of hair follicles into the resting (telogen) phase simultaneously. About 2–3 months later, you notice significant shedding. This is telogen effluvium.
The good news: it’s almost always temporary. Hair typically regrows within 6–9 months once the trigger is removed or resolved. The difficult part is identifying the cause, since the shedding occurs weeks to months after the event itself.
- Identify and address the underlying trigger (stress, illness, diet)
- Support regrowth with adequate protein (at least 50g/day)
- Consider biotin, zinc, and iron if levels are low
- Be patient — recovery takes 3–6 months
- See a dermatologist if shedding exceeds 9 months
Hormonal Changes
Hormones are perhaps the biggest non-genetic driver of hair loss. Pregnancy causes a surge in estrogen that keeps hairs in the growth phase — which is why many women enjoy thick hair during pregnancy. After delivery, estrogen drops sharply, and those retained hairs shed all at once (postpartum hair loss). This is very common and resolves on its own.
Menopause, polycystic ovary syndrome (PCOS), and stopping or starting hormonal birth control can all trigger significant shedding by altering the balance of androgens and estrogens in the scalp.
- Get hormone levels tested (estrogen, testosterone, DHEA-S, prolactin)
- For PCOS: treat the underlying condition (often with metformin or spironolactone)
- Postpartum loss typically resolves by month 12 — focus on nutrition
- Discuss HRT with your doctor during perimenopause/menopause
Thyroid Disorders
Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) are well-documented causes of hair loss. Thyroid hormones regulate nearly every cellular process in the body — including hair follicle cycling. When thyroid function is disrupted, the hair growth cycle is disrupted with it.
Hair loss from thyroid problems is typically diffuse — thinning all over the scalp rather than in patches. The loss can be significant before other thyroid symptoms (fatigue, weight changes, temperature sensitivity) become obvious.
- Ask your doctor for a full thyroid panel (TSH, Free T3, Free T4, thyroid antibodies)
- Treating the thyroid disorder typically reverses hair loss within 6–12 months
- Avoid excess iodine supplementation without medical guidance
Nutritional Deficiencies
Hair follicles are among the most metabolically active cells in the body — they need a steady supply of nutrients to function. Deficiencies in iron (especially in premenopausal women), zinc, vitamin D, biotin, and protein are all linked to hair loss and thinning.
Crash dieting is a particularly common culprit, as it often restricts both calories and key micronutrients simultaneously. Vegetarian and vegan diets can also increase risk if iron and B12 intake isn’t carefully managed.
- Get blood work: ferritin, zinc, vitamin D, B12, folate
- Aim for ferritin levels above 40 ng/mL for optimal hair growth
- Ensure adequate protein: 0.8–1g per kg of body weight daily
- Don’t supplement blindly — excess vitamin A can actually cause hair loss
- A hair-specific supplement (Nutrafol, Viviscal) may help fill gaps
Alopecia Areata
An autoimmune condition in which the immune system mistakenly attacks hair follicles, causing sudden, patchy hair loss — usually in round or oval patches on the scalp. It affects roughly 2% of the global population at some point in their lifetime, and can affect people of any age.
In some cases it progresses to alopecia totalis (loss of all scalp hair) or alopecia universalis (loss of all body hair), though many people experience only a few patches that regrow spontaneously. Stress is a known trigger for flares.
- See a dermatologist — this requires professional diagnosis
- Corticosteroid injections into affected patches: first-line treatment
- JAK inhibitors (baricitinib, ritlecitinib) — newer FDA-approved options for moderate-severe cases
- Topical immunotherapy for widespread loss
- Manage stress: documented to reduce flare frequency
Scalp Conditions
An unhealthy scalp environment can disrupt the hair growth cycle. Seborrheic dermatitis (dandruff), scalp psoriasis, and fungal infections like tinea capitis (ringworm of the scalp) all inflame the scalp and can interfere with follicle health. Tinea capitis is particularly common in children and causes patchy hair loss with scaling and sometimes breakage at the hair shaft.
Folliculitis — inflammation of the hair follicles — can also cause permanent scarring if left untreated.
- Antifungal shampoos (ketoconazole, selenium sulfide) for dandruff and fungal infections
- Tinea capitis requires oral antifungals (griseofulvin, terbinafine)
- Medicated scalp treatments for psoriasis
- Keep scalp clean and moisturized; avoid harsh chemicals
- See a dermatologist promptly for any inflamed or scabbed areas on the scalp
Medications & Medical Treatments
A wide range of medications list hair loss as a side effect. Chemotherapy drugs are the most well-known — they target rapidly dividing cells, which includes hair follicles. But many other drugs can cause thinning or shedding, including blood thinners (heparin, warfarin), antidepressants, beta-blockers, lithium, retinoids (isotretinoin), and some cholesterol medications.
Radiation therapy to the head also causes hair loss in the treated area, which may be permanent if the dose is high enough to damage follicle stem cells.
- Review all medications with your doctor or pharmacist
- Do not stop prescribed medication without medical guidance
- Often a dosage adjustment or switch to an alternative drug resolves the issue
- Scalp cooling during chemotherapy reduces (but doesn’t eliminate) chemo hair loss
- Hair typically regrows 3–6 months after stopping the causative drug
Hairstyling & Traction Alopecia
Repeated tension on hair follicles from tight hairstyles — braids, weaves, ponytails, dreadlocks, or extensions — causes traction alopecia. Initially reversible, traction alopecia can become permanent if the traction continues long-term and scar tissue forms around the follicles.
Heat damage, chemical relaxers, and bleach can also break hair shafts and thin the appearance of hair — though this isn’t true follicle loss in the same way. Still, the cumulative damage weakens strands significantly.
- Avoid or alternate tight hairstyles; give scalp regular breaks
- Early traction alopecia is reversible — act quickly
- Use heat protectant sprays; limit heat styling to 2–3x per week
- Deep condition regularly to strengthen existing hair
- See a dermatologist if hairline has noticeably receded
Autoimmune & Other Medical Conditions
Beyond alopecia areata, several systemic autoimmune diseases cause hair loss as a symptom. Lupus can cause scarring alopecia (permanent follicle destruction), as well as non-scarring diffuse loss. Celiac disease, when undiagnosed and untreated, leads to nutrient malabsorption that starves follicles. Diabetes and inflammatory bowel disease (IBD) are also associated with hair thinning.
If hair loss is accompanied by fatigue, joint pain, unexplained weight changes, or rashes, an underlying systemic condition should be investigated.
- Comprehensive blood panel: CBC, ANA, anti-dsDNA, CRP, ESR, blood glucose, celiac antibodies
- Treating the underlying condition is the primary intervention
- Work with a rheumatologist or specialist alongside your dermatologist
- Hair loss from lupus may require immunosuppressant therapy
See a Doctor Promptly If: you notice sudden patchy hair loss, rapid overall thinning, scalp inflammation or scarring, hair loss accompanied by fatigue or other symptoms, or loss in a child. Scarring alopecias cause permanent follicle damage — early intervention matters.
When to See a Doctor About Hair Loss
- Sudden or patchy hair loss
- Visible scalp where hair was once dense
- Loss accompanied by fatigue or weight changes
- Scalp itching, burning, or scaling
- Hair loss in a child or teenager
- Loss after starting a new medication
- Shedding continuing for more than 3 months
- Any signs of infection on the scalp
Supporting Healthy Hair: Universal Tips
Regardless of the cause, certain habits support hair follicle health across the board. Getting 7–9 hours of sleep allows growth hormone — which supports tissue repair including follicle health — to peak during deep sleep stages. Chronic sleep deprivation elevates cortisol, which is antagonistic to hair growth.
Scalp massage (even 4 minutes daily) has been shown in small studies to increase hair thickness, likely by stretching follicle cells and improving blood flow. It’s low-effort and has no downsides.
Hydration matters more than most people realize. Hair shafts are about 25% water, and even mild dehydration reduces strand flexibility and increases breakage. Aim for at least 8 glasses daily — more if you’re active.
Finally, manage what you can control: chronic stress is one of the most underappreciated drivers of hair loss. Regular exercise, meditation, and adequate social connection are not luxuries — they’re physiological regulators that directly affect hair cycle signaling.
Frequently Asked Questions
