Losing between 50 and 150 hairs a day is completely normal. Your hair goes through a constant cycle of growing, resting, and falling out, so finding strands on your pillow, in the shower drain, or on your clothes is expected. When shedding consistently exceeds that range, or you notice thinning spots and changes in your hairline, something is pushing more of your hair into its shedding phase than usual. The good news: most causes of excessive shedding are temporary and reversible once you identify the trigger.
How the Hair Growth Cycle Works
Understanding why hair sheds starts with how it grows. Each strand on your head moves independently through four phases. About 85% to 90% of your hair is in the active growing phase at any given time, which lasts anywhere from two to seven years. A small fraction (1% to 3%) is in a brief transition phase, and roughly 9% is resting. After resting for a few months, each hair naturally releases from the follicle and falls out, making room for a new strand to take its place.
Excessive shedding happens when something disrupts this cycle and forces a larger-than-normal percentage of hairs into the resting and shedding phases all at once. Instead of the usual 50 to 150 strands a day, you might lose handfuls. Dermatologists call this telogen effluvium, and it’s the single most common reason people suddenly notice dramatically more hair in their brush.
Stress, Illness, and Delayed Shedding
The most frustrating thing about stress-related shedding is the delay. A major stressor, whether physical or emotional, pushes hair follicles into their resting phase. But the hair doesn’t actually fall out until two to three months later. By the time you’re alarmed by the shedding, you may have forgotten the event that caused it. Common triggers include high fevers, severe infections, major surgery, and intense psychological stress.
This type of shedding typically lasts fewer than six months. Once the stressor passes and your body recalibrates, the follicles re-enter their growth phase and new hair comes in. You don’t need treatment in most cases; you need time. If shedding continues beyond six months, that points to an ongoing trigger that hasn’t been resolved, like chronic stress or an untreated thyroid problem.
Hormonal Shifts
Hormones are one of the most powerful influences on your hair cycle. During pregnancy, high estrogen levels keep hair locked in the growing phase much longer than usual. Hair feels thicker and fuller because strands that would normally shed are staying put. After delivery, estrogen drops sharply, and all those extra hairs enter the resting phase at once. The result is dramatic shedding that typically peaks three to four months postpartum. It looks alarming, but it’s your hair returning to its pre-pregnancy baseline, not true hair loss.
Thyroid imbalances, both overactive and underactive, also disrupt the growth cycle. Starting or stopping birth control pills can have a similar effect because these medications alter hormone levels that directly influence hair follicles. If your shedding started within a few months of any hormonal change, that’s likely your answer.
Nutritional Gaps That Starve Follicles
Hair follicles are metabolically demanding. They need a steady supply of nutrients to sustain the growing phase, and iron is at the top of that list. Your body stores iron as ferritin, and research suggests that ferritin levels need to be above 70 ng/mL to fully support normal hair cycling. Many people, especially those who menstruate, fall well below that threshold without being technically anemic. Levels between 21 and 70 ng/mL can be adequate for basic body functions but still too low to keep hair in its growth phase.
Crash diets and restrictive eating patterns are another frequent culprit. Protein is a building block of hair, and diets that cut protein significantly can trigger shedding within a few months. Deficiencies in zinc, vitamin D, and B vitamins have also been linked to increased hair fall. If your shedding coincides with a major dietary change, that connection is worth exploring with a blood test.
Scalp Conditions and Inflammation
A healthy scalp is the foundation of healthy hair growth, and chronic inflammation can quietly sabotage it. Seborrheic dermatitis, a common condition that causes flaky, itchy, irritated skin on the scalp, damages hair follicles and hinders their ability to produce hair normally. The condition ramps up oil production, which feeds a naturally occurring yeast on the skin called Malassezia. When that yeast overgrows, it creates a cycle of inflammation that weakens follicles.
The itching itself compounds the problem. Scratching an irritated scalp physically damages follicles, obstructing natural growth and causing hair to fall out. If your shedding comes with persistent flaking, redness, or itchiness, treating the scalp condition often reduces the shedding significantly. Medicated shampoos targeting the yeast and inflammation are the typical first step.
Medications That Trigger Shedding
Several commonly prescribed medications list hair shedding as a side effect. Retinoids (used for acne and skin conditions), certain blood pressure medications, anticoagulants, mood stabilizers, and some antifungal drugs can all push follicles into the resting phase prematurely. The shedding pattern looks identical to stress-related hair loss: diffuse thinning across the scalp that starts a few months after beginning the medication.
If you started a new medication two to four months before the shedding began, it’s worth bringing up with your prescriber. In many cases, hair regrows within a few months of switching to an alternative. Stopping a medication without guidance can cause its own problems, so this is a conversation, not a solo decision.
How to Tell If Your Shedding Is Excessive
You don’t need to count every strand that falls. A simple at-home check: run your fingers through clean, dry hair and tug gently. One or two hairs in your hand is normal. If you’re consistently pulling out more than that in a single pass, your shedding is likely above the normal range. Dermatologists use a more standardized version of this test, grasping about 40 strands and pulling gently. Six or more strands coming loose indicates active hair loss that warrants investigation.
Other signs that your shedding has crossed from normal to excessive include a widening part, a thinner ponytail, visible scalp where you couldn’t see it before, and scalp tenderness or irritation. Pay attention to timing. If you can trace the shedding back to a specific event, illness, dietary change, new medication, or hormonal shift roughly two to three months before it started, you’ve likely identified the cause. That timeline is the signature of telogen effluvium and the most useful clue you can bring to a dermatologist if the shedding doesn’t resolve on its own.