Losing between 50 and 150 hairs per day is completely normal. Every strand on your head is on its own timeline, cycling through growth and rest independently, so a certain amount of daily shedding is just the cost of having hair. But if you’re pulling clumps from your brush, clogging your shower drain more than usual, or noticing your ponytail getting thinner, something may be pushing more of your hair into its shedding phase at once.
How Your Hair’s Growth Cycle Works
Each hair follicle cycles through three phases on its own schedule. The growth phase (anagen) lasts 3 to 10 years and determines how long your hair can get. After that, the follicle enters a brief transition phase (catagen) lasting 2 to 3 weeks, where the hair stops growing and detaches from its blood supply. Then comes the resting phase (telogen), which lasts 3 to 4 months. At the end of telogen, the old hair falls out and a new one begins growing in its place.
At any given time, about 85 to 90 percent of your hair is in the growth phase and the rest is resting or preparing to shed. That balance is what keeps shedding at a steady, barely noticeable rate. Problems start when something disrupts the cycle and forces a larger-than-normal percentage of follicles into the resting phase simultaneously. When those hairs all reach the end of telogen around the same time, you get a wave of shedding that feels alarming.
Stress and Illness: The Most Common Trigger
The most frequent cause of sudden, excessive shedding is a condition called telogen effluvium. A physical or emotional stressor pushes a large batch of hair follicles out of their growth phase and into rest all at once. Because the resting phase lasts about three months, the shedding doesn’t start right away. It typically hits two to three months after the triggering event, which makes it easy to miss the connection.
Common triggers include high fevers, surgery, significant weight loss, severe emotional stress, stopping birth control, and illness (COVID-19 became a well-known trigger during the pandemic). The tricky part is that by the time your hair starts falling out, you may have already recovered from whatever caused it, so the shedding seems to come out of nowhere. Acute telogen effluvium usually resolves on its own within six months as new growth replaces what was lost.
Postpartum Shedding
If you recently had a baby, the timing of your shedding probably isn’t a coincidence. During pregnancy, elevated estrogen levels keep hair in the growth phase longer than usual, which is why many people notice thicker hair while pregnant. After delivery, those hormone levels drop and all the hair that was “held back” enters the resting phase together. Postpartum shedding typically starts about three months after giving birth and resolves on its own between 6 and 12 months postpartum. It can look dramatic, but it’s your hair returning to its pre-pregnancy baseline, not true hair loss.
Iron Levels and Nutritional Gaps
Your hair follicles are among the fastest-dividing cells in your body, which makes them sensitive to nutritional shortfalls. Iron is the nutrient most closely linked to hair shedding, and the threshold is higher than many people realize. You don’t need to be anemic for low iron to affect your hair. Research suggests that ferritin (your body’s stored iron) needs to be above 70 ng/mL for a healthy hair cycle. Many people, especially those who menstruate, fall below that level without ever being flagged as iron-deficient on routine bloodwork because standard lab ranges often set the “normal” cutoff much lower.
Protein deficiency, very low calorie diets, and inadequate levels of vitamin D, zinc, and B12 can also contribute. Crash dieting is a particularly common culprit. If you dramatically cut calories or eliminated a food group in the months before shedding started, that’s worth noting.
Thyroid Problems
Your thyroid hormones play a direct role in keeping hair follicles in their growth phase. They stimulate the cells responsible for building the hair shaft and suppress the signals that tell a follicle to stop growing. When thyroid hormone levels are too low (hypothyroidism) or too high (hyperthyroidism), hair follicles lose that support and can shift into their resting phase prematurely. The shedding tends to be diffuse, meaning it thins evenly across the scalp rather than creating bald patches. If your shedding is accompanied by fatigue, unexplained weight changes, feeling unusually cold or hot, or changes in your skin, a simple blood test can check your thyroid function.
Scalp Conditions
An itchy, flaky, or inflamed scalp can contribute to shedding in a more mechanical way. Conditions like seborrheic dermatitis (a common form of persistent dandruff) cause irritation that leads to scratching. That scratching physically loosens hairs and can break the skin, creating a cycle of inflammation and shedding. The hair loss from scalp conditions like this isn’t permanent. Once the underlying inflammation is treated and the scratching stops, regrowth follows.
How to Tell Shedding From Breakage
Not all hair you find on your pillow or in your brush was actually shed from the root. Sometimes it’s breakage from heat styling, chemical treatments, or rough handling, and that distinction matters because the causes and solutions are different.
Look at the strand itself. A naturally shed hair is typically full length (close to the length of the rest of your hair) and has a small white or translucent bulb at one end. That bulb is the root end where it was anchored to your scalp. A broken hair is shorter, and both ends will look smooth or frayed with no bulb. If most of what you’re finding is short fragments without bulbs, breakage is likely the bigger issue, and the fix is about how you’re treating your hair rather than what’s happening internally.
A Simple Way to Gauge Your Shedding
Dermatologists use a version of what’s called the gentle hair pull test, and you can do a rough version at home to get a sense of whether your shedding is within a normal range. Run your fingers through a small section of clean, dry hair (about 40 to 60 strands) and pull gently from root to tip. Normally, zero to two hairs come out. If you’re consistently pulling out six or more hairs per section across different areas of your scalp, that suggests an elevated rate of shedding worth investigating.
Keep in mind that washing your hair less frequently makes shedding look worse than it is. If you wash every three or four days, the hair that would have fallen out gradually over those days collects and comes out all at once in the shower. That clump in the drain may represent several days’ worth of normal shedding rather than a single day’s loss.
What to Do About Excessive Shedding
If your shedding started suddenly and you can trace it back to a specific event (illness, surgery, major stress, childbirth, a crash diet), time is often the primary treatment. The hair cycle needs months to reset, and new growth that started after the trigger has already begun working its way out. Most people see noticeable improvement within six to nine months.
If your shedding has been going on for longer than six months, is gradually worsening, or doesn’t have an obvious trigger, it’s worth getting bloodwork done. A basic panel checking ferritin, thyroid hormones, vitamin D, and a complete blood count can rule in or out the most common underlying causes. Many of these are straightforward to correct once identified.
In the meantime, be gentle with your hair. Avoid tight hairstyles that put tension on the roots, minimize heat styling, and skip harsh chemical treatments until the shedding settles. These won’t fix an internal cause, but they prevent you from adding mechanical damage on top of what’s already happening.