Losing between 50 and 150 hairs a day is completely normal. Your hair grows in cycles, and at any given time about 9% of the hairs on your scalp are in a resting phase, ready to fall out and make room for new growth. If you’re finding clumps in the shower drain or noticing your ponytail getting thinner, something has likely pushed more of your hair into that resting phase at once, a pattern that can double or triple your daily shedding.
Stress-Related Shedding Has a Delay
The most common reason for a sudden increase in shedding is a condition called telogen effluvium, where a physical or emotional stressor forces hair follicles out of their growth phase early. After a triggering event, up to 70% of actively growing hairs can shift into the resting phase at the same time. The catch is that the shedding doesn’t start right away. There’s typically a two- to three-month gap between the stressor and the moment you notice hair falling out, which makes it hard to connect the dots.
This means the event responsible for your shedding may have happened months ago. Common triggers include high fevers, severe infections (COVID-19 included), major surgery, intense psychological stress, and crash diets that cut protein too aggressively. The good news is that this type of shedding is almost always temporary. Once the trigger resolves, hair typically regrows on its own over six to twelve months.
Hormonal Shifts Are a Major Driver
Your thyroid gland has an outsized influence on hair growth. Both an overactive thyroid and an underactive thyroid can cause diffuse thinning across the entire scalp rather than patchy bald spots. If you’re also experiencing unexplained fatigue, weight changes, or sensitivity to cold or heat, a thyroid imbalance is worth investigating. Shedding from thyroid disorders follows the same telogen effluvium pattern, pushing more follicles into the resting phase simultaneously.
Stopping or starting hormonal birth control is another well-documented trigger. When you discontinue the pill, the drop in hormones can prompt a wave of shedding that begins a few months later. Similarly, any medication that alters your hormone balance can shift the growth cycle.
Postpartum Hair Loss
If you recently had a baby, the timing is not a coincidence. During pregnancy, elevated estrogen keeps more hair in the growth phase than usual, which is why many people notice thicker hair while pregnant. After delivery, those hormone levels drop and all that “extra” hair enters the resting phase at once. Postpartum shedding usually starts around three months after giving birth and resolves on its own within six to twelve months as hormone levels stabilize.
Low Iron and Nutritional Gaps
Iron deficiency is one of the most underrecognized causes of hair shedding, particularly in women who menstruate. Dermatologists often look at ferritin levels (your body’s stored iron) and consider supplementation when levels fall below 70 ng/mL, even if standard blood work says your iron is technically “in range.” That’s because the threshold for healthy hair is higher than the threshold for avoiding anemia.
Ferritin testing has a limitation worth knowing about: if you have any kind of chronic inflammation, ferritin can read artificially high, masking a true deficiency. If your shedding doesn’t have an obvious explanation and your ferritin level is borderline, it’s reasonable to ask for a more thorough workup. Zinc and vitamin D deficiencies can also contribute to shedding, though iron tends to be the bigger culprit.
Medications That Cause Shedding
Several common drug classes list hair loss as a side effect, and the connection isn’t always obvious because of that two- to three-month delay. Retinoids used for acne or psoriasis are among the most frequent offenders. In studies of higher-dose retinoid therapy, more than 60% of patients experienced noticeable hair loss, though it reversed after stopping the medication. Even at lower doses used for acne, roughly 3% to 6% of patients report thinning.
Other categories to be aware of include beta-blockers and calcium channel blockers (prescribed for blood pressure and heart conditions), certain antidepressants, mood stabilizers like valproic acid (which causes hair loss in roughly 11% of users), and long-term antifungal treatments. If you started a new medication a few months before your shedding began, the timing may be more than coincidental.
Scalp Conditions That Damage Follicles
Sometimes the problem is on the surface. Seborrheic dermatitis, a chronic condition that causes flaky, oily, inflamed patches on the scalp, can directly damage hair follicles and obstruct new growth. The inflammation comes from excess oil production on the scalp, which feeds a naturally occurring yeast called Malassezia. When that yeast overgrows, it triggers more inflammation, more itching, and more damage in a self-reinforcing cycle.
Scratching an itchy scalp compounds the problem by physically harming the follicles. If your shedding comes alongside persistent dandruff, redness, or greasy flakes, treating the scalp condition itself often slows the hair loss. Medicated shampoos targeting the yeast and inflammation are typically the first step.
How to Tell If Your Shedding Is Abnormal
Counting individual hairs is impractical, but there’s a simple test dermatologists use that you can try at home. Grasp a small section of about 40 hairs between your fingers, close to the scalp, and pull gently but firmly through to the ends. If six or more strands come out, that section of your scalp has active, above-normal shedding. Repeat in a few different areas to see if the pattern is widespread or localized.
Context matters too. If you wash your hair less frequently, you’ll naturally see more hair come out on wash days because loose hairs have been accumulating. That alone doesn’t mean something is wrong. What should prompt a closer look is a noticeable change from your own baseline: a ponytail that feels half as thick, visible scalp where you didn’t see it before, or shedding that persists beyond a few months without improvement. A blood panel checking thyroid function, iron and ferritin levels, and vitamin D can quickly rule in or out the most common treatable causes.