Telogen Effluvium: Why Hair Sheds Suddenly and When It Grows Back

Telogen effluvium is sudden, even shedding all over the scalp that starts a few months after a shock to the body, such as an infection, an operation, childbirth or a crash diet.^[1][2] Many follicles switch from growing to resting at the same time and later let go of their hairs together.^[3] The follicles are not destroyed, and in most people the hair grows back.^[4]

Below: why the shedding comes late, how long it lasts, how it differs from pattern hair loss, and why a hair transplant is the wrong answer while you are still shedding.

Causes and Timeline of Telogen Effluvium

How the Hair Cycle Explains the Delay

Each scalp hair moves through a growing phase called anagenGlossaryAnagen is the growing phase of the hair cycle. For scalp hair it lasts 2 to 6 years according to a Deutsches Ärzteblatt review, and 2 to 7 years according to Cleveland Clinic.
Open in the glossary →, a short transition called catagenGlossaryCatagen is the short transition phase of the hair cycle, lasting about 1 to 2 weeks. Cell division stops and about two thirds of the lower follicle breaks down, while the dermal papilla stays intact and moves upward.
Open in the glossary → and a resting phase called telogenGlossaryTelogen is the resting phase of the hair cycle. It lasts 2 to 4 months according to a Deutsches Ärzteblatt review, and up to 4 months according to Cleveland Clinic.
Open in the glossary →, after which the old club hair is shed.^[8] In a biopsy study, 6.5% of terminal hairs were resting in 22 people without hair loss, against 11% in chronic telogen effluvium.^[9]

A trigger pushes a large share of growing follicles into the resting phase together.^[3] Those hairs fall weeks or months later, and that delay is what makes the cause so hard to spot.^[10]

Common Triggers

Triggers described in the research include:

• Infection: after COVID-19, shedding began a mean of 74 days after the first symptoms, sooner than the classic timing.^[11]
• Surgery and anaesthesia: a 2026 review links general anaesthesia to telogen effluvium, though high-quality studies are lacking.^[12]
• Sudden weight loss: a recognised trigger.^[1] After weight loss surgery, 47% of 7,044 patients in 41 studies had hair loss, more often after gastric bypass than after a sleeve.^[13] For injections, see Mounjaro hair loss.
• Childbirth: often named as a trigger^[1], yet a 2016 review found no published data showing that shedding differs between pregnant and postpartum women.^[14] Our postpartum hair loss guide covers it in full.
• Starting a medicine: reviews single out retinoids, antifungals and psychotropic drugs^[10], plus anticoagulants and blood pressure medicines.^[15] See Adderall hair loss and Wellbutrin hair loss.
• Stopping a medicine: shedding often follows stopping drugs that prolong the growing phase, such as the contraceptive pill.^[16] See can birth control cause hair loss.
• Thyroid problems: blood tests are used to rule out endocrine causes.^[7] Our page on thyroid hair loss lists the tests.
• Emotional strain: one man charted 31 months of stressful events, and his shedding flared and settled with them.^[17]

How Long Telogen Effluvium Lasts, Month by Month

Short regrowing hairs often appear while the shedding is still going on: trichoscopy found them in 61.2% of people with post-COVID shedding.^[20] How soon the length returns depends on how fast hair grows.

Acute vs Chronic Telogen Effluvium

Acute shedding has a clear start and settles within months; past six months it is called chronic.^[19] In Whiting's study of 355 patients, chronic telogen effluvium mostly affected women aged 30 to 60, began abruptly, with or without an obvious trigger, and ran a long, fluctuating course.^[9]

Whether it is a separate disease is disputed. A 2023 systematic review of 1,628 cases, 97.5% of them women, found no agreed definition and suggests many are early female pattern hair loss, an undetected trigger, or worry about normal shedding in anxious people with long hair.^[21]

Telogen Effluvium vs Androgenetic Alopecia and Other Look-Alikes

Telogen Effluvium or Pattern Hair Loss?

Androgenetic alopeciaGlossaryAndrogenetic alopecia, or pattern baldness, is the pattern hair loss behind most male and female thinning. It is primarily driven by genetic predisposition and sensitivity to androgen hormones.
Open in the glossary →, or pattern hair loss, is the main condition to tell apart from telogen effluvium, and the two often occur together.^[23] The shed-hair and biopsy rows come from studies of the chronic form; the wash test compared it with female pattern hair loss.

Diffuse alopecia areataGlossaryAlopecia areata is an autoimmune condition that can cause round patches of hair loss in the eyebrows, beard or scalp. Hair often regrows within a few months and may look white or grey at first before the natural colour returns.
Open in the glossary → can mimic it too: alopecia areata incognita causes sudden heavy shedding and diffuse thinning, and usually responds to topical steroids.^[26] Our alopecia areata entry covers the patchy form.

How Doctors Confirm It

1. History: what happened in the months before the shedding. Its duration also predicts which tests are worth doing.^[6]
2. Pull test: in 181 volunteers, a gentle pull removed 0.44 hairs on average, and the authors set the normal limit at 2 or fewer.^[27]
3. Wash test: you skip washing for 5 days, then collect every hair shed in one shampoo.^[25] The modified version also counts fine vellus hairs, to separate telogen effluvium from pattern loss or spot both.^[28]
4. Trichoscopy: a scalp magnifier often shows empty follicles and short regrowing hairs.^[11]
5. Blood tests and biopsy: bloods exclude endocrine, nutritional and autoimmune causes^[7]; a biopsy can find early pattern hair loss when the picture is unclear.^[6]

Iron, Vitamin D and Supplements: Where the Studies Disagree

A 2026 meta-analysis found lower ferritin, the body's iron store, and lower vitamin D in people with telogen effluvium than in controls.^[29] Two controlled studies disagree. In one, iron deficiency was no more common in chronic telogen effluvium than in women without hair loss^[30]; in another, 90 women with chronic shedding had ferritin and vitamin D no different from controls, but lower zinc.^[2]

Whether correcting low ferritin brings hair back is unknown.^[30] Test first, treat a confirmed deficiency, and read our guide to vitamins for hair loss. Across 14 studies, commercial supplements raised the share of growing hairs but not the total hair count.^[31]

Telogen Effluvium in Women

Women see dermatologists for telogen effluvium more often^[7] and made up 67.5% of 465 post-COVID cases in a systematic review.^[11]

If your parting keeps widening after the shedding settles, read our entry on female pattern hair loss.

Telogen Effluvium in Men

Men get it too: they were 27.5% of a 2026 series of 69 people treated for post-COVID shedding.^[32] The usual question is whether it is a shed or early male pattern baldness. Diffuse thinning without bare patches points to telogen effluvium^[3]; patterned thinning^[24] is covered in DHT hair loss.

Treatment, Regrowth and the Hair Transplant Question

What Helps Telogen Effluvium

Finding and stopping the cause is the main treatment, because diffuse effluvium usually settles once the trigger is gone.^[24] There is still no targeted, evidence-based drug for it.^[1][18] The minoxidil studies we found are small and have no placebo group:

• Topical 5% minoxidil: in 12 patients using it twice a day for 24 weeks, terminal hairs rose by 12.55 per cm² by week 4, and nearly 70% improved on the wash test. The authors say natural recovery and the small sample limit what this proves, and that the use is off-label.^[18]
• Low-dose oral minoxidil: in 36 women with chronic shedding taking 0.25 to 2.5 mg a day, shedding scores fell at 6 and 12 months, and 13 grew unwanted facial hair.^[19] In 69 people with post-COVID shedding, the episode resolved in a median of 93 days.^[32]

Our minoxidil entry explains the forms, doses and side effects.

Shedding After Surgery and After a Hair Transplant

A hair transplant can cause a local form of shedding, called shock lossGlossaryShock loss is a temporary shedding phase after a hair transplant, triggered by surgical stress to the scalp and typically starting 2 to 4 weeks after the procedure. The follicles remain healthy beneath the skin, and new growth resumes within 4 to 6 months.
Open in the glossary →, at the recipient site or in the donor area.^[33][34] In 621 people who had FUE, 23 (3.7%) developed shock loss at the recipient site. Women were far more likely to be affected, and their risk rose with age, most of all over 40 with female pattern hair loss.^[33]

A scoping review put effluvium at up to 4.1% at the donor site and 6.5% at the recipient site.^[34] Our guide to shock loss after a hair transplant gives the full timeline.

When Shedding Doesn't Stop: Is a Transplant the Answer?

For telogen effluvium alone, no. In the seven-year follow-up above, the four women who kept shedding lost no visible density and their follicles did not shrink^[22], so there was no bald area for grafts to fill.

The answer changes when the shed uncovers pattern hair loss. One woman in that study developed it within 18 months^[22], and a 2023 review suggests many cases labelled chronic telogen effluvium are early pattern loss.^[21] Treatment then follows that diagnosis, with finasteride among the options for men.^[24] A transplant can be weighed for areas that stay thin after the shedding stops.

Frequently Asked Questions

Who Needs Patience, and Who Needs a Closer Look

Most people with telogen effluvium need time and a search for the trigger, not surgery, because diffuse shedding usually settles once the cause is removed.^[24] Get checked sooner if shedding passes six months or your parting keeps widening, since that points to chronic shedding or pattern hair loss.^[19][21] Bare patches suggest alopecia areata instead.^[24]

A transplant only makes sense once pattern hair loss is confirmed and the shedding has settled. If you are not sure which you have, send us three photos for a free hair analysis. The medical team will tell you whether it looks like a temporary shed or pattern hair loss underneath. You can also message us on WhatsApp.