Most of us take our hair’s growth cycle for granted — strands grow, rest, and shed in a steady rhythm. But sometimes that rhythm gets thrown off. You might notice that your hair isn’t growing as long as it used to, or that it seems to be shedding more than usual in certain seasons. This isn’t random. It often means the different phases of the hair growth cycle — anagen, catagen, and telogen — are out of sync.
Understanding how these phases work can help you spot when something is off and take steps to support your hair through the process. Let’s explore what the hair growth cycle actually looks like, why it can become disrupted, and what you can do about it.
The three phases of hair growth
Each hair follicle on your scalp operates on its own timeline. The cycle has three main stages:
- Anagen (growth phase): This is the active growing stage, lasting anywhere from two to seven years. The longer this phase lasts, the longer your hair can grow. About 85 to 90 percent of your scalp hairs are in anagen at any given time.
- Catagen (transition phase): A short transitional stage that lasts about two weeks. The hair follicle shrinks and detaches from the blood supply. Only about 1 percent of hairs are in this phase at once.
- Telogen (resting and shedding phase): Lasts around three to four months. During this phase, the hair is fully formed but no longer growing. At the end, the old hair sheds to make room for a new anagen hair. Normally, about 10 to 15 percent of hairs are in telogen.
When everything is working well, these phases flow seamlessly. But when they fall out of balance — for example, when too many hairs enter telogen at once, or when anagen shortens — you see changes in volume, length, and shedding patterns.
What throws hair growth phases out of sync?
Several factors can disrupt the normal timing of the hair cycle. Some are temporary, while others may require more attention.
Stress and telogen effluvium
One of the most common causes of sync disruption is a condition called telogen effluvium. After a period of significant physical or emotional stress — such as illness, surgery, childbirth, or extreme weight loss — your body can shift a large number of hairs into the telogen phase prematurely. The result is noticeable shedding that usually occurs two to three months after the triggering event. This is usually temporary, and the cycle often resets on its own once the stressor is resolved.
Nutritional imbalances
Your hair follicles are among the most metabolically active cells in your body. They require a steady supply of nutrients to sustain the anagen phase. Deficiencies in iron, zinc, vitamin D, and certain B vitamins can shorten the growth phase and push more hairs into resting or shedding phases prematurely. Crash diets or very low-calorie eating patterns can also trigger temporary shedding.
Hormonal shifts
Hormones play a powerful role in the hair cycle. Changes in thyroid hormones, sex hormones (like estrogen and androgens), and cortisol can all alter the timing of growth phases. For example, during menopause, declining estrogen levels can shorten the anagen phase, leading to thinner hair over time. Androgenetic alopecia (pattern hair loss) is driven by the effect of dihydrotestosterone (DHT) on genetically susceptible follicles, gradually miniaturizing hairs and shortening the growth cycle.
Medications and health conditions
Certain medications — including some antidepressants, blood thinners, beta-blockers, and chemotherapy drugs — can interfere with the hair cycle. Autoimmune conditions like alopecia areata directly attack hair follicles, causing sudden patchy hair loss. Scalp issues such as seborrheic dermatitis or fungal infections can also disrupt the local environment and affect growth timing.
Signs your hair growth cycle may be off
Because the hair cycle is gradual, the signs can be subtle at first. Look for:
- Increased shedding when you shower or brush — especially if it started several weeks after a stressful event.
- Hair that seems to stop growing at a certain length (indicating a shortened anagen phase).
- More broken hairs or thinner overall density, particularly at the crown or temples.
- Changes in texture — hair that was once straight may become wavy or frizzy during certain seasons due to shifts in the follicle’s activity.
A note on seasonal shedding: It’s normal to shed a bit more in late summer and early fall. This is likely a remnant of an evolutionary cycle — slightly more hairs exit telogen during these months. A mild increase is nothing to worry about, but if shedding is dramatic or persistent, it’s worth investigating.
What you can do to help restore balance
You cannot directly command your hair follicles to stay in anagen longer, but you can create conditions that support a healthy cycle.
Prioritize nutrient-rich eating. Focus on adequate protein (hair is made of keratin), iron-rich foods like spinach and lean red meat, and sources of zinc and vitamin C. Many experts suggest checking iron and vitamin D levels with a simple blood test if you’re noticing changes.
Manage stress. Since stress is a major trigger for telogen effluvium, finding ways to lower your baseline stress — through sleep, movement, and relaxation practices — can indirectly protect your hair cycle.
Be gentle with your hair. Avoid harsh chemical treatments, excessive heat styling, or tight hairstyles that can stress the follicle. A healthy scalp environment helps the hair cycle run smoothly.
Talk to a healthcare provider if shedding persists. If you’ve been shedding heavily for more than three months, or if you notice patchy hair loss, it’s a good idea to see a dermatologist. They can check for underlying conditions like thyroid disorders or nutrient deficiencies and offer guidance tailored to your situation.
Most disruptions to the hair growth cycle are temporary and resolve once the underlying cause is addressed. With patience and consistent care, it’s possible to get your hair’s natural rhythm back on track.
