Understanding the Hair Growth Cycle
If you’ve ever wondered why hair growth feels so slow, or why you can’t seem to see results from a new routine right away, the answer lies in biology.
Your hair doesn’t grow all at once. It moves through a continuous cycle of growth, rest, and release. Each strand on your head is at a different point in this journey at any given moment. And once you understand how this cycle works, everything about hair care starts to make more sense.
This isn’t just science for science’s sake. Understanding your hair growth cycle is genuinely empowering. It helps you set realistic expectations, recognize what’s normal, and trust the process when results aren’t immediate.
The Hair Growth Cycle: An Overview
Every single hair follicle on your scalp goes through four distinct phases. These phases happen independently, which is why you’re not shedding all your hair at once or growing it all at the same rate.
According to research published in the Journal of Investigative Dermatology, this cycle is influenced by genetics, hormones, nutrition, stress, and overall health. The length of each phase varies from person to person, which is why some people can grow hair down to their waist while others find their hair “stuck” at a certain length.
Let’s break down each phase.
Phase 1: Anagen (The Growth Phase)
This is the active phase when your hair is actually growing. Cells in the hair follicle divide rapidly, pushing the hair shaft up and out of the scalp.
The anagen phase lasts anywhere from 2 to 7 years, depending on your genetics. The length of this phase determines the maximum length your hair can reach. Someone with a longer anagen phase can grow longer hair. Someone with a shorter anagen phase will find their hair reaches a certain length and stops.
At any given time, about 85 to 90 percent of the hair on your head is in the anagen phase. This is the phase you want to support and protect, because the longer hair stays in active growth, the longer and healthier it can become.
What influences the anagen phase: Nutrition, hormone balance, blood flow to the scalp, and overall health all play a role in how long hair stays in this phase and how robust the growth is.
Phase 2: Catagen (The Transition Phase)
Once a hair strand has finished its growth cycle, it enters the catagen phase. This is a short transitional period lasting about 2 to 3 weeks.
During catagen, the hair follicle shrinks and detaches from the blood supply (called the dermal papilla) that nourishes it. The hair stops growing but doesn’t fall out yet. It’s essentially in a holding pattern, preparing to move into the resting phase.
Only about 1 to 2 percent of your hair is in the catagen phase at any time. There’s not much you can do to influence this phase directly, but supporting overall follicle health helps ensure the transition happens smoothly.
Phase 3: Telogen (The Resting Phase)
The telogen phase is when hair is fully at rest. The strand remains in the follicle but isn’t growing. Meanwhile, a new hair may begin forming beneath it.
This phase lasts about 3 months. Roughly 10 to 15 percent of your hair is in the telogen phase at any given time.
This is the phase that gets disrupted when you experience stress, illness, hormonal shifts, or nutritional deficiencies. A condition called telogen effluvium occurs when a higher-than-normal percentage of hairs are pushed prematurely into the resting phase, leading to noticeable shedding a few months later.
Understanding this timing is key. If you went through a stressful period or illness 2 to 3 months ago, increased shedding now is likely telogen effluvium. It’s your body catching up to what happened internally, not a sign that something is currently wrong.
Phase 4: Exogen (The Shedding Phase)
The exogen phase is sometimes considered part of telogen, but it’s the distinct period when hair actually releases from the follicle and falls out. This makes room for new growth.
According to the American Academy of Dermatology, it’s normal to shed 50 to 100 hairs per day. This sounds like a lot, but considering you have about 100,000 hair follicles on your head, it’s a small percentage.
Shedding is not the same as hair loss. Shedding is a natural, healthy part of the cycle. Hair loss occurs when something disrupts the cycle and new hairs aren’t replacing the ones that fall out.
Why This Matters for Your Hair Routine
Once you understand the growth cycle, a few things become clear:
Results take time. If you start a new supplement or routine today, it’s supporting the hair that’s currently forming in the follicle. That hair won’t be visible above your scalp for weeks, and it won’t show meaningful length for months. This isn’t a flaw in the product. It’s how hair biology works.
Shedding is normal. Seeing hair in your brush or shower drain isn’t automatically cause for concern. It’s part of the exogen phase. What matters is whether new hair is growing to replace it.
Consistency is essential. Because the cycle operates over months, stopping and starting a routine means you never give your follicles sustained support. The anagen phase needs ongoing nourishment to thrive.
Internal health shows up in your hair. Your hair is a reflection of what’s happening inside your body. Stress, sleep, nutrition, and hormones all influence how long hair stays in the growth phase and how strong it grows.
Supporting Each Phase
While you can’t control your genetics, you can create an environment that supports healthy cycling:
For the anagen phase: Focus on nutrition. Protein, iron, zinc, biotin, vitamin D, and omega-3 fatty acids all play a role in hair growth. A study published in Dermatology Practical & Conceptual found that nutritional deficiencies are a common underlying factor in hair thinning.
For the catagen and telogen phases: Minimize stress where possible. Chronic stress can push more hairs into the resting phase prematurely. Prioritizing sleep and stress management supports healthy cycling.
For the exogen phase: Be gentle with your hair. Avoid harsh styling, excessive heat, and tight hairstyles that can cause breakage or traction. Let shedding happen naturally without aggressive brushing.
For overall scalp health: A healthy scalp supports healthy follicles. Keep it clean, moisturized, and free of buildup. Think of your scalp like soil: the better the environment, the better things grow.
Summary
Your hair is always in motion, cycling through phases of growth, rest, and renewal. This process has been happening since before you were born and will continue throughout your life.
Understanding the cycle doesn’t just help you make sense of your hair. It helps you trust the process. When you know that results take time, that shedding is normal, and that your daily habits are supporting something you can’t see yet, patience becomes easier.
Growth is happening. Even when you can’t see it yet.
