What Is the Anagen Phase of Hair Growth?

Definition of Anagen Phase

Wind blown hair
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What is the Anagen Phase?

The anagen phase is the active growth phase of hair follicles. The cells in the root of the hair are dividing rapidly, adding to the hair shaft.

  • Pronunciation: ANN-uh-jin

What Happens During the Anagen Phase of Hair Growth?

During this phase the hair grows about one centimeter, or about half of an inch, every 28 days. Scalp hair stays in this active phase of growth for two to six years.

If you didn't trim your hair, it would grow to a full length of 18 to 30 inches.

The amount of time the hair follicle stays in the anagen phase is genetically determined. Some people have longer anagen phases and can grow hair very long, while others will never see their hair get much longer than a foot and a half. At the end of the anagen phase an unknown signal causes the follicle to go into the catagen phase.

At any time, about 80-90% of the hairs on your head are in anagen phase

From the Anagen Phase to the Catagen Phase

The catagen phase is a short transition stage that occurs at the end of the anagen phase. It signals the end of the active growth of a hair. The hair detaches from its blood supply during the catagen phase. This phase lasts for about 2-3 weeks while a club hair is formed. 

  • Pronunciation: KAT-uh-jin

Telogen Phase - Dormant Phase Before the Anagen Phase

After the short catagen phase, the hair is released and the hair follicle rests for three months.

The club hair falls out. Typically, you lose 50 to 100 hairs per day. After three months, the follicle goes back into anagen phase and begins to grow a new hair.

What Can Shorten Your Anagen Phase?

People who are on a calorie-restricted diet may shorten their anagen phase. This can also happen due to stress, childbirth or traumatic events.

More hair follicles go into the telogen phase at the same time and you can see diffuse hair loss, known as telogen effluvium. There can also be anagen effluvium from chemotherapy, radiation or toxic chemicals. These disrupt the hair while it is in anagen phase. In these cases, the hair will usually recover to its prior fullness. Repeated bouts of dieting or chemotherapy etc. would continue the pattern.

There are rare cases of people with short anagen syndrome, where they can never grow longer hair because for unknown reasons they have a very short anagen phase. These people will say they have never needed a haircut.

Loose Anagen Syndrome

Loose anagen syndrome is seen in some children. They have sparse hair and their hair is easily pulled out, with the roots showing they are in anagen phase. It may be an inherited condition. It usually improves as the child ages.

Anagen Stimulators

Some hair products may claim to be anagen stimulators, to support or induce hairs to go into the anagen phase or to stay in the anagen phase longer.

For over-the-counter products, it is explained in ways so it won't be judged to be a health claim but rather a marketing term. Look for peer-reviewed research that supports any such claims.


Kanwar AJ, Narang T. "Anagen effluvium." Indian J Dermatol Venereol Leprol. 2013 Sep-Oct;79(5):604-12. doi: 10.4103/0378-6323.116728.

Giacomini F, Starace M, Tosti A. "Short anagen syndrome." Pediatr Dermatol. 2011 Mar-Apr;28(2):133-4. doi: 10.1111/j.1525-1470.2010.01165.x.

Li VW, Baden HP, Kvedar JC. "Loose anagen syndrome and loose anagen hair." Dermatol Clin. 1996 Oct;14(4):745-51.

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