The 4 Stages of Hair Growth: Anagen, Catagen, Telogen & Exogen

Stages of Hair Growth at a Glance

The exact percentages vary between studies and individuals. Exogen is also different from the other stages because it describes the shedding event itself and can overlap with the end of telogen and the beginning of a new anagen cycle rather than occupying a neatly separated percentage of scalp follicles.

Anagen: The Growth Phase

Anagen is the active growing phase of the hair cycle. On the scalp, it usually lasts several years and contains the large majority of hair follicles at any one time.

During anagen, cells in the lower part of the hair follicle divide rapidly and produce the hair shaft—the visible strand that eventually emerges from the scalp.

At the base of the follicle is the dermal papilla, a specialized group of cells involved in signaling and regulating follicle activity. A 2023 review in the Journal of Clinical Medicine describes the dermal papilla as an important regulator of the matrix cells responsible for producing the hair shaft.

Scalp hair grows at roughly 1 cm per month, although individual growth rates vary. The eventual length of an uncut hair therefore depends largely on how long that follicle stays in anagen.

This is also why scalp hair can become much longer than eyebrow or body hair: scalp follicles normally stay in anagen for years, while follicles elsewhere on the body have much shorter growth periods.

At what stage does hair grow the longest? Hair grows during the anagen phase, which is by far the longest stage of the scalp hair cycle. The longer a follicle remains in anagen, the longer the hair shaft can potentially become before the cycle moves into its transition and resting stages.

You cannot reliably prove that an individual hair is in anagen simply by looking at it in the mirror. However, continuing length, stable density, and visible new growth are consistent with active follicles.

Catagen: The Transition Phase

Catagen is a short transition phase lasting roughly two to three weeks and usually accounting for only a small percentage of scalp follicles.

Once anagen ends, active hair production slows and then stops.

The lower portion of the follicle begins to regress, cellular activity decreases, and the relationship between the growing follicle and the dermal papilla changes. Programmed cell death, or apoptosis, plays an important role in this controlled regression.

The existing hair does not immediately fall out. Instead, the follicle prepares to enter its resting state.

<span”>From a person’s point of view, catagen is almost impossible to identify without specialized examination because it is short and normally affects only a small fraction of hairs at the same time.

That is important when trying to “diagnose” your hair cycle at home: seeing several hairs fall out does not mean your whole scalp has entered catagen. Human scalp follicles normally cycle independently rather than changing phase together.

Telogen: The Resting Phase

Telogen is the resting phase of hair growth. It generally lasts around two to four months, with roughly 5–10% of healthy scalp hairs in telogen at a given time.

The follicle is relatively inactive during this stage, and the existing hair remains inside it as a mature club hair.

Eventually, the follicle prepares for another growth cycle. A new anagen hair may begin developing below the older resting hair before that old strand is released.

Telogen is especially important when understanding sudden diffuse shedding.

A physical or physiological stressor can cause more follicles than usual to leave anagen and enter telogen. Because telogen lasts for months, the resulting shedding may not become noticeable until well after the original trigger.

This pattern is known as telogen effluvium.

Possible triggers include major illness, high fever, childbirth, significant psychological stress, surgery, substantial weight loss, nutritional problems, hormonal changes, and some medications.

Normal shedding is different from excessive shedding. The American Academy of Dermatology notes that losing approximately 50–100 hairs per day can fall within the normal range, although wash frequency, brushing habits, hair density, and individual variation can affect how noticeable that loss appears.

If you are trying to decide whether the amount you see in the shower or on your brush is expected, see how much hair shedding is normal. [Internal URL pending in content plan]

Exogen: The Shedding Phase

Exogen is the phase in which the old hair shaft is released from the follicle and falls out.

Unlike anagen, catagen, and telogen, exogen does not always behave like a completely separate block of time.

Modern descriptions of the cycle distinguish the physical shedding process from the resting phase. The old strand can be released while a new anagen hair is beginning its journey through the same follicular unit.

This explains why shedding alone does not automatically mean the follicle has stopped working.

The visible hair shaft can fall while the follicle underneath remains healthy and capable of producing another hair.

Problems become more concerning when shedding is:

·         suddenly much heavier than usual,

·         persistent for months,

·         associated with progressive loss of density,

·         concentrated in clearly defined bald patches,

·         accompanied by redness, pain, scaling, or scarring,

·         or occurring alongside other unexplained physical symptoms.

Those patterns require evaluation of the cause, not simply identification of the normal hair-cycle phase.

Why Do Some Sources Say There Are 3 Stages of Hair Growth?

You may see both three-stage and four-stage models when reading about the hair growth cycle.

Neither automatically means the other source is wrong.

The traditional three-stage model describes:

1.        Anagen: growth

2.       Catagen: transition

3.       Telogen: rest

In that model, shedding is usually described as part of late telogen or the transition into the next growth cycle.

The four-stage model separates exogen, the release of the old hair shaft, from telogen.

A 2023 clinical review explicitly describes the hair cycle as four primary phases—anagen, catagen, telogen, and exogen—while other dermatology references continue to teach the three major follicular phases and describe shedding at the end of telogen.

For understanding what you actually see happening to your hair, the four-stage model is useful because it separates resting from visible shedding.

How to Tell What Stage Your Hair Is In

There is no accurate at-home test that can tell you the exact phase of every follicle on your scalp.

Instead, think in terms of patterns.

Not Sure What Your Hair Is Telling You?

If you’re noticing unusual shedding, thinning, or changes in density, a professional assessment can help identify what may be affecting your hair growth cycle.

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Signs consistent with active growth

Hair that continues to lengthen over time and areas showing gradual new growth suggest that follicles are actively producing hair.

However, one short hair is not enough to prove anagen. Short strands can also be caused by breakage.

Signs associated with telogen or exogen

An increase in full-length hairs coming out during washing, brushing, or normal handling can reflect increased shedding.

Telogen hairs typically have a club-shaped root, but examining shed hairs at home is not a reliable substitute for professional assessment.

If shedding appears a few months after illness, major stress, childbirth, surgery, rapid weight change, or another significant event, telogen effluvium may be considered.

What about catagen?

Catagen is too short and affects too few follicles to produce an obvious everyday “catagen look.”

How doctors assess the cycle

When necessary, dermatologists can use the history of the hair loss together with scalp examination, trichoscopy, hair-pull testing, a trichogram, laboratory testing, and occasionally biopsy to identify the pattern and likely cause.

A patch of complete hair loss, progressive recession, widening of the part, or ongoing diffuse thinning should not be explained away simply as “your hair being in the wrong phase.”

What Can Disrupt the Normal Hair Growth Cycle?

Many conditions change hair by altering how long follicles remain in different stages rather than immediately destroying the follicle.

Chemotherapy and Radiotherapy

Many chemotherapy drugs target rapidly dividing cells. Hair-matrix cells are also highly active during anagen, making growing hairs particularly vulnerable.

This can cause anagen effluvium, a rapid form of hair loss that often begins within weeks of chemotherapy. Radiation involving the scalp can also disrupt actively growing follicles.

Hair commonly begins to grow again after treatment ends, although the timeline and completeness of regrowth depend on the treatment involved.

Stress, Age, Hormones, and Nutrition

Hair cycling responds to both internal and external signals.

A major physiological or psychological stressor can shift more hairs from anagen toward telogen, resulting in delayed shedding. Age can also shorten the duration of anagen, while hormonal signaling plays an important role in conditions such as androgenetic alopecia.

Nutritional deficiency can also contribute to hair problems, but that does not mean everyone experiencing shedding benefits from taking supplements.

The 2023 clinical review found associations between hair loss and nutritional deficiencies while also noting limited evidence that supplementation benefits otherwise healthy people without a deficiency.

This is an appropriate point to connect readers to evidence-based content about biotin, hair vitamins, and nutritional deficiencies rather than presenting supplements as a universal solution.

What about Gen Z hair loss?

There is no separate “Gen Z hair cycle.”

When younger adults experience thinning or shedding, the same medical factors still need to be considered: genetics, stress, illness, restrictive diets or nutritional deficiency, hormonal conditions, medications, damaging hair practices, and other causes.

A generational label should therefore not replace an individual assessment of why the hair cycle has changed.

Waxing, Shaving, and Hair Transplantation

Shaving does not reset the follicle’s growth cycle. It cuts the hair shaft at skin level and does not make the underlying follicle produce hair faster, darker, or thicker.

Waxing is different because the strand is removed from the follicle rather than cut at the surface. The time before visible regrowth therefore depends partly on where that follicle is in its cycle.

Hair transplantation produces another distinctive situation. Following transplantation, grafted follicles can move from anagen toward telogen, causing the visible transplanted hairs to shed during the first few weeks. New growth commonly follows after a resting period. A surgical review describes shedding beginning around weeks two to four with new growth after a lag of roughly three months.

Minoxidil and the Hair Cycle

Minoxidil is closely linked to searches about the hair growth cycle because one proposed effect is to encourage follicles to move from telogen toward anagen and to prolong growth activity.

Research reviews describe shortening of telogen and prolongation of anagen among the proposed mechanisms, although the drug’s complete mechanism remains incompletely understood.

This transition also helps explain why some users notice temporary early shedding after starting treatment.

For a full discussion of effectiveness, timing, safety, and initial shedding, see does minoxidil work.

How to Support the Anagen Phase of Hair Growth

There is no proven method that permanently locks every follicle into anagen.

The better goal is to identify anything that is unnecessarily shortening the growth phase or pushing too many follicles toward rest.

1. Identify the cause of abnormal shedding first

 telogen effluvium, alopecia areata, nutritional deficiency, inflammatory scalp disease, medication-related loss, and scarring alopecia require different approaches.

Treating the wrong cause can waste months while thinning continues.

2. Meet nutritional needs rather than taking supplements blindly

Adequate energy, protein, vitamins, and minerals support normal tissue function.

When a clinically relevant deficiency is present, correcting it may be important. Taking increasingly large doses of biotin, iron, zinc, or other supplements without evidence of deficiency is not the same as treating the cause of hair loss.

3. Reduce avoidable physical damage

Tight hairstyles, repeated traction, aggressive chemical processing, and excessive heat can damage the hair shaft and, in some circumstances, the follicle.

Reducing breakage does not technically “extend anagen,” but it helps preserve the hair that the follicle successfully produces.

4. Address major stressors and underlying health problems

Persistent stress, major illness, endocrine disorders, and other systemic problems can influence hair cycling.

If shedding began after a significant event, the timing matters because telogen-related loss may appear months after the trigger rather than immediately.

5. Use evidence-based treatments when they match the diagnosis

Treatments such as minoxidil can support growth in certain hair-loss conditions, but they are not appropriate for every cause of shedding.

Treatment should be selected according to the diagnosis, medical history, scalp condition, and potential risks—not simply because a product is described as an “anagen booster.”

For a broader look at treatment and recovery options, see regrow hair.

The hair cycle is not simply “growing” versus “falling out.”

Healthy follicles continuously move through anagen growth, catagen transition, telogen rest, and exogen shedding, and each follicle follows its own schedule.

Understanding those stages can make normal shedding less confusing—but the cycle should not be used to dismiss sudden, persistent, patchy, or progressive hair loss.

When the normal balance changes, the useful question is not only “Which stage is my hair in?” but also “Why have more follicles moved into that stage?”

Finding that cause is the first step toward understanding whether the hair is following a normal cycle or whether treatment may be needed.

Take the Next Step for Your Hair

Understanding the cause of hair loss is the first step toward choosing the right approach. Speak with a Padra specialist for a personalized assessment of your hair and scalp.

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