When men spot a bunch of hair lying in state on their bathroom floor, they usually ask themselves two questions. First, has it really been that long since I last vacuumed around here? And more importantly, why the heck is so much of my hair on the ground and not on my head?

Both are really good questions to ask, especially if you’ve been struggling with hair loss. But as frustrating as it is to see your hair falling out, studies have shown that you’re not alone. In fact, some experts have found that even the average person loses up to 100 hairs per day.

We don’t have to tell you that’s a lot of hair to lose. But at that rate, shouldn’t most of us be bald by now? The short answers are “absolutely not” and “maybe you should take a walk around the block.” But the more useful (and scientific) answer is that our hair is constantly going through four stages of growth—and part of that involves losing some of it.

  • Anagen: the growth phase
  • Catagen: the involution phase
  • Telogen: the resting phase
  • Exogen: the shedding phase

Let’s take a closer look at those four stages, the timelines for each one, and why it’s really important for some of your hair to fall out throughout the process.

Anagen Phase: Two to Six Years

Your hair is constantly growing during the anagen phase, at the average rate of ½ inch per month. The length of your anagen phase determines the maximum length of your hair. For most people, that can be anywhere between 18 to 30 inches.

Typically, these growth cycles occur every two to six years. We don’t need to tell you that it’s a long time for your hair to grow. But if our hair grows back that frequently, how can we explain things like hair loss and male pattern baldness? Those answers lie in the following phases of hair growth.

The Catagen Phase: A Few Weeks

Once your hair is done growing, it goes into a transition known as the catagen phase. And by “transition,” we mean that this is when your hair begins the process of falling out.

As horrible as that might sound, the science behind it is pretty interesting. Your hair gets a signal from your body that tells it to stop growing, which your follicles respond to by shrinking slightly and detaching themselves from the blood supply.

When you see the word “detach,” you probably assume that your hair just kind of falls out at this stage and you’re doomed to be bald forever. The good news is that while it does detach itself from the scalp, it usually doesn’t fall out until new hair begins to push it upward.

Telogen Phase: Three Months

After your hair is done detaching itself from your scalp, it enters a state of rest called the telogen phase. That resting period is pretty serious business and would put any college student’s nap schedule to shame. That’s because your dying hair just sits on your head for three to five months before it’s pushed out by brand new hair.

This stage is far from straightforward, however. Researchers at Harvard Medical School described a condition called telogen effluvium. That’s a very fancy term to describe the phenomenon where a body change or an unexpected stressor accelerates the telogen phase. Someone with telogen effluvium might lose upwards of 300 hairs per day, compared to the typical 100 per day we mentioned earlier.

Exogen Phase: A Few Days

Your hair has been through a lot by the time it reaches the exogen stage. Once your new hair grows in, the old hair completely detaches from your scalp and begins to fall out in larger quantities. While you’ll notice this most frequently after combing your hair, you’ll also see bundles of hair in your shower drain or while styling your hair.

How Does Hair Loss Affect These Stages?

As you might have guessed, all hair growth cycles are not created equal. When male pattern baldness sets in, hair follicles get smaller, which makes it harder for hair to grow. Additionally, Dr. Antonella Tosti, a Keeps medical advisor and hair loss expert, says the anagen stage gets shorter and the telogen stage stays the same or even increases.

As research shows, this stage reversal has everything to do with your genetics. While this means you can’t control if you’ll be affected, you can stop it from getting worse by treating it.

How Does Hair Loss Treatment Affect These Stages?

And speaking of treatments, there are two FDA-approved treatments to stop hair loss: finasteride and minoxidil.

Before we get to the “how,” let’s talk quickly about DHT. DHT is a male sex hormone that usually helps your body develop things like muscles and facial hair. In men with male pattern baldness, DHT goes a little haywire. It starts attaching to your hair follicles and making them smaller and smaller until they can no longer grow hair.

DHT doesn’t do this alone however. Like every evil villain, it does it with the help of a sidekick, an enzyme called 5α-reductase. Finasteride stops 5α-reductase from ever forming. This means that DHT can’t get that boost it needs to miniaturize your hair follicles.

Now, minoxidil works a little differently. It helps to increase the size of the anagen follicles (remember male pattern baldness happens when those follicles get smaller and smaller) and decrease how long the telogen phase lasts. This means that your hair is getting healthier and growing more often. It also means that you might notice what’s called “minoxidil shedding” for the first few months after you start using it, but that’s just your old thinning hair making way for new, healthy hair.


We’ve talked through a lot of science here, and for good reason. We’re not here to scare you into thinking that you’re doomed to male pattern baldness forever once your hair growth process changes.

Every guy’s hair grows (and falls out) at different rates, but everyone goes through the same stages. And because of that, understanding each stage of hair growth makes it easier to evaluate your own hair loss and better understand how hair loss treatments can help.


The information provided in this article is not a substitute for professional medical advice, diagnosis, or treatment. You should not rely upon the content provided in this article for specific medical advice. If you have any questions or concerns, please talk to your doctor.

Finasteride is an oral medication used to treat male pattern baldness in men only. It is not for use by women. When used by men, finasteride is generally safe but it can also cause serious side effects, including but not limited to allergic reactions, sexual dysfunction, and high-grade prostate cancer. Most patients find that problems with sexual function resolve when they stop taking the medicine. For full prescribing information, view the drug label information.

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