Hair Growth Cycle: Anagen, Catagen, Telogen and Exogen Explained

The hair growth cycle is the loop every follicle repeats: years of growth, a short shutdown, months of rest, then release of the old hair.^[1][2] Your roughly 100,000 scalp follicles each run it on their own clock, so you shed a little every day but never all at once.^[1]

The Phases of the Hair Growth Cycle

Sources give different ranges:

Anagen: The Growth Phase

Short hairs such as eyelashes have a short 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 →, while scalp anagen lasts years.^[8] Its length sets how long a hair can grow.^[1] Monthly growth is covered in how fast hair grows.

Catagen, Telogen, Exogen and Kenogen

In 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 → the follicle regresses; in 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 → it rests, holding a club hair that is later released.^[2][9] Exogen, the release phase, was first described in mice^[10]; human exogen hairs are only passively held.^[6]

Kenogen is the gap when the follicle stays empty before a new anagen hair emerges.^[11]

Why Your Hairs Do Not All Shed at Once

Each follicle changes phase independently, at intervals that vary at random around an average.^[12] A 2023 review lists these triggers for an early switch to telogen.^[2]

• Inflammation
• Hormones and stress
• Poor nutrition or sleep
• Medicines that block cell division

When many follicles switch together, the shedding shows 2 to 4 months later.^[1] Our telogen effluvium entry covers that shedding.

How Pattern Hair Loss Changes the Cycle

Shorter Growth, Longer Empty Spells

In pattern hair lossGlossaryAndrogenetic 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 →, more and more hairs get a shorter anagen, grow finer and wait longer before regrowing, a finding from almost 10,000 cycles followed in 10 men over 15 years.^[13] Ageing does the same, less markedly.^[14]

Following 43 men for 2.5 years, one team proposed that longer, more frequent kenogen is what thins the scalp.^[15] Why some follicles react is covered in DHT and hair loss.

Can You Extend or Restart the Hair Growth Cycle?

In animals, minoxidil shortens telogen so resting follicles enter anagen early, and it may prolong anagen.^[16] In 212 men, finasteride 1 mg a day improved the ratio of growing to resting hairs by 47% over placebo at 48 weeks.^[17]

In a four-year study, though, finasteride cut the empty lag phase by 40% and lengthened anagen in thick hairs by 23%, but follicles already making hairs under 40 micrometres kept shrinking.^[18]

The Hair Growth Cycle After a Hair Transplant

Why Transplanted Hair Sheds, Then Regrows

Moved follicles keep their genetic traits, a principle called donor dominance.^[19] Their hairs still usually shed 2 to 4 weeks after surgery, and regrowth begins 3 to 5 months after it.^[20]

Month by month, see our hair transplant recovery timeline. Native hair can shed too: in one center's 621 patients, 23 had shock loss, and women were at far higher risk.^[21]

When a Transplant Is the Wrong Answer

A transplant adds follicles; it does not treat the native hair around them, so surgeons pair it with medical therapy to maintain density.^[19] It is also the wrong move during acute telogen effluvium, which usually lasts up to 6 months.^[22]

Frequently Asked Questions

When a Changing Cycle Needs a Closer Look

Steady daily shedding is the cycle at work, and a sudden shed usually settles within 6 months.^[22] Finer, shorter hairs in a pattern point to a shortening cycle^[13], which finasteride can reverse in follicles that still make thick hair.^[18]

Send us three photos for a free hair analysis: the medical team will tell you whether this is normal cycling, a temporary shed or progressive loss, and whether a transplant fits. Or message us on WhatsApp.