The Hair Growth Cycle, Explained Plainly
Somebody asked me this in the chair at least once a week for twenty-three years, usually while looking at the floor.
"Is that normal?"
They meant the hair on the cape, or in the shower drain, or wound around the brush. And the honest answer is that you cannot tell whether it is normal until you understand what your head is actually doing, because what it is doing is stranger than most people assume.
Here is the whole thing, without the diagram and without the sales pitch.
Every follicle is on its own clock
Start here, because everything else follows from it.
A dog moults. A deer moults. Their coats work on a shared schedule, so the whole animal sheds at once and grows back at once. Human scalp follicles do not do this. Each one runs its own independent cycle, out of step with its neighbours.
That is why you are not bald every spring. It is also why loss is so hard to notice — the follicles that are resting are scattered evenly across your head rather than clustered, so nothing looks empty until a great many of them are resting at the same time.
The cycle has three phases. Everyone in the industry knows the names and almost nobody explains what they mean for you.
Anagen — the growing phase
This is the long one. A follicle in anagen is actively building hair, pushing it up and out at roughly half an inch a month, and it stays in this phase for somewhere between two and seven years.
At any given moment, the large majority of your follicles are in anagen. That is why you have hair.
The length of your anagen phase is largely inherited, and it is the single most underappreciated fact about hair. Your maximum hair length is set by how long your follicles stay in anagen.
Do the arithmetic. Half an inch a month for two years is twelve inches — about collarbone. Half an inch a month for six years is thirty-six inches — past the waist. Same growth rate. Wildly different outcome.
I had clients who genuinely could not understand why their hair "stopped growing" at the shoulder no matter what they bought. Their hair had not stopped growing. It was reaching the end of its anagen phase and being released, on schedule, exactly as designed. There is no product that extends a genetically short anagen phase, and the ones implying otherwise are selling to people who have never been told this.
If your hair reaches a certain length and then seems to stall, there are only two real explanations: it is being released at the end of its cycle, or it is breaking at the ends as fast as it grows at the root. Those look identical in the mirror and they are completely different problems. That is the next piece in this series.
Catagen — the transition
Short, unglamorous, about two to three weeks. The follicle stops producing, detaches from its blood supply, and shrinks. A small fraction of your follicles are in catagen at any moment.
Nothing you can do reaches this phase and nothing you notice happens during it. I mention it only because leaving it out makes the cycle look like a two-step process, and it isn't.
Telogen — the resting phase
The follicle sits idle for roughly three months with the finished hair still anchored in it. Then it releases that hair and starts a new anagen phase underneath.
Here is the part that matters: the hair you shed is not the hair that is falling out. It is the hair that finished, months ago. By the time a telogen hair leaves your head, the replacement is often already growing beneath it — which is why you sometimes find a shed hair with a small pale bulb at the end and a new short hair standing up in the same spot.
Where "fifty to a hundred a day" comes from
People quote this number constantly without knowing what it is. It is not a rule handed down from anywhere. It is arithmetic, and you can do it yourself.
``` ~100,000 follicles on an average scalp × ~10% in telogen at any given time = ~10,000 resting follicles ÷ ~100 days in the telogen phase = ~100 hairs released per day ```
Change the inputs and the number changes with them. A person with fine, dense hair may have well over 100,000 follicles and shed proportionally more. Someone with coarse, sparse hair sheds fewer. The famous number describes an average scalp and nothing about your scalp specifically.
Which is why I stopped telling people to count.
Why the shower drain lies to you
Counting is worse than useless because washing does not change how much you shed. It changes when you notice.
Hairs released while you sleep or sit at a desk stay in your hair, held there by the hairs around them, until something moves them. Washing and brushing are what move them. So the person who washes daily finds a modest amount every day, and the person who washes twice a week finds an alarming amount twice a week — and the second person is not losing more hair. They are collecting three days of it at once.
I watched clients terrify themselves by switching to less frequent washing, seeing the drain, and concluding the new routine was destroying their hair. Same total. Different accounting.
The number that actually means something is not how much comes out. It is how much is still there.
What to look at instead
Three things, all free, all better than counting.
Your part. Widening at the crown, over months, is real information. Take a photo in the same light, same place, every couple of months. Memory is a terrible instrument and photographs are not.
Your ponytail. Whatever you normally use to tie it — if it took two turns of the elastic a year ago and takes four now, that is a measurement.
Your hairline and temples. Recession is easier to see in a photo than in a mirror, because you look at your own face too often to notice slow change.
The three-month rule, in both directions
The cycle takes months, so everything to do with hair takes months.
A stress, an illness, a crash diet, a nutritional shortfall — none of these show up in your hair when they happen. They show up when the affected follicles finish their resting phase and let go, which is generally two to four months later. That delay is the single most useful thing on this page and it gets its own piece in this series.
It also runs the other way. Fix the cause today and you will not see the benefit today. New hair has to be built and then grow far enough out to be visible, which is another few months on top. Anyone promising visible change in two weeks is either describing how your hair looks rather than how much of it there is, or they are not describing anything at all.
What the cycle does not tell you
Being straight about the limits of this: understanding the cycle explains why shedding happens. It does not tell you whether your shedding is normal, and I cannot tell you that either.
Some things are genuinely outside the ordinary run of things and belong with a doctor rather than a stylist — sudden loss, patchy loss, loss with scaling, redness or soreness, loss alongside fatigue or weight change or a new medication. Those are not cycle problems and no amount of understanding anagen will help.
If you want to turn a vague worry into a number, the tests worth asking for by name are in Scalp Care: The Part Everyone Skips. It is a short, cheap, unexotic list and it beats guessing.
I am a hairdresser and not a doctor. What I can tell you is what twenty-three years of looking at the backs of people's heads taught me, which is that most of the panic in that chair was about a cycle working exactly as it should — and the cases that were not, looked different.
Next: Shedding vs. Breakage — how to tell which one you have, in about thirty seconds, with a lamp.
As an Amazon Associate I earn from qualifying purchases. Nothing on this page is medical advice.
What to do next
If the timing does not fit a normal cycle, work out whether it is shedding or breakage first — they need completely different answers. If it is shedding and it has been going on for months, the scalp page covers the tests worth asking for, and the laser cap page covers the one non-prescription device I use myself.