Losing between 50 and 150 hairs a day is normal, even if it looks alarming in your shower drain or hairbrush. But if you’re noticing clumps on your pillow, thinning all over your scalp, or handfuls coming out when you run your fingers through your hair, something has likely pushed more of your hair follicles into their shedding phase than usual. The most common cause is a condition called telogen effluvium, a temporary but unsettling wave of hair loss triggered by stress, illness, hormonal shifts, or nutritional gaps.
Why Hair Sheds in Waves
Your hair follicles cycle independently through three phases: growing, transitioning, and resting. At any given time, about 85 to 90 percent of your hair is in the growing phase, which lasts two to six years. The rest is in a resting phase that lasts a few months before the strand falls out and a new one replaces it.
When your body experiences a significant physiological stress, it can force a large number of follicles out of the growing phase and into the resting phase all at once. Two to three months later, all of those resting hairs fall out in a noticeable wave. This delay is what makes the shedding so confusing: the trigger happened months ago, but the hair loss is happening now. People often can’t connect the dots because the stressful event feels like old news by the time the shedding starts.
The Most Common Triggers
Think back two to three months before the shedding started. That’s when the trigger likely occurred. The most frequent culprits include:
- High fever or severe illness. COVID, flu, and other infections with sustained high fevers are well-documented triggers.
- Major psychological stress. A death in the family, job loss, financial crisis, or prolonged anxiety can be enough.
- Surgery or physical trauma. The body treats major surgery as a significant physical stress.
- Childbirth. Postpartum shedding is one of the most common forms (more on this below).
- Thyroid problems. Both an overactive and underactive thyroid can trigger excessive shedding.
- Crash diets or low protein intake. Fad diets that cut calories or protein too aggressively starve hair follicles of what they need.
- Stopping birth control pills. The hormonal shift after discontinuing oral contraceptives mimics the same mechanism as postpartum hair loss.
- Certain medications. Some blood pressure medications, antidepressants, anti-inflammatory drugs, and acne treatments can push follicles into the resting phase.
Postpartum Hair Loss
If you recently had a baby, this is almost certainly what’s happening. During pregnancy, elevated estrogen levels extend the growing phase, which is why many pregnant women notice thicker, fuller hair. After delivery, estrogen drops back to normal levels, and all the hair that was “held” in the growing phase enters the shedding phase at once. It typically starts around three months after giving birth and resolves on its own within 6 to 12 months. No treatment is necessary, though it can be emotionally distressing when you’re already adjusting to life with a newborn.
Thyroid Problems and Hair Texture Changes
Thyroid dysfunction deserves special attention because it’s a common, treatable cause that people often miss. Both hypothyroidism and hyperthyroidism can cause diffuse thinning across the entire scalp rather than bald patches. Beyond the shedding itself, thyroid-related hair loss often changes the texture of your hair. Strands may feel drier, coarser, and more brittle than usual. If you’re also experiencing fatigue, unexplained weight changes, feeling unusually cold or hot, or changes in your skin, a simple blood test can check your thyroid function.
Nutritional Gaps That Affect Hair
Your hair follicles are metabolically active and sensitive to what’s circulating in your blood. Two deficiencies stand out as particularly relevant to shedding.
Iron is the big one. You don’t need to be anemic for low iron to affect your hair. Research shows that iron stores (measured by a blood marker called ferritin) in the range of 21 to 70 ng/mL may be technically “adequate” by standard lab ranges but still too low to support a normal hair growth cycle. Many labs flag ferritin as normal at 10 to 15 ng/mL, but hair researchers have found that levels below 70 ng/mL can contribute to shedding. This is especially relevant for women with heavy periods, vegetarians, and frequent blood donors.
Vitamin D plays a role in creating the cells that form hair follicles. If your levels are low, supplementation may help, but it’s worth getting tested rather than guessing. A simple blood panel covering ferritin, vitamin D, and thyroid function can rule out or confirm the most common medical causes of increased shedding.
What About Biotin Supplements?
Biotin is marketed aggressively for hair growth, but the evidence doesn’t support it for people who aren’t actually biotin-deficient. A review in the Journal of Clinical and Aesthetic Dermatology found no studies demonstrating that biotin supplementation benefits hair growth in healthy adults with sufficient biotin levels. The highest-quality study reviewed, a double-blind placebo-controlled trial, found no difference between the biotin and placebo groups. True biotin deficiency is rare in adults eating a varied diet. Spending money on biotin supplements when the real issue is low iron or thyroid dysfunction means the actual problem goes unaddressed.
How To Tell If Your Shedding Is Abnormal
Counting individual hairs isn’t practical, but there’s a simple screening method dermatologists use called the pull test. Grasp a small section of about 40 hairs between your fingers and gently tug from root to tip. If one or two strands come out, that’s normal turnover. If six or more strands come out from a single section, that suggests active hair loss worth investigating. Try this in a few different areas of your scalp, since shedding patterns can vary.
Other signs that your shedding has crossed into abnormal territory: your ponytail feels noticeably thinner, you can see more of your scalp than usual (especially at the part line), or the volume of hair collecting in your drain has clearly increased over several weeks.
Recovery Timeline
The reassuring news is that telogen effluvium is almost always temporary. Once the underlying trigger is resolved, whether that means recovering from illness, managing stress, correcting a nutritional deficiency, or adjusting a medication, the shedding typically slows over a few months. New growth begins replacing what was lost, though it takes time for those short new hairs to reach a length where your hair feels full again. Most people notice significant improvement within six to nine months of addressing the cause.
The shedding itself can last two to four months even after the trigger is gone, because hair that already entered the resting phase needs to complete that cycle before falling out. This means things may seem to get worse before they get better, which is normal. If shedding continues beyond six months without improvement, or if you notice patchy bald spots rather than diffuse thinning, that points to a different type of hair loss that needs a dermatologist’s evaluation.