Hair shedding between 50 and 150 strands per day is completely normal. If you’re noticing clumps in the shower drain, more hair on your pillow, or thinning that you can see, something has likely pushed more of your hair follicles into their resting phase at once. The most common culprits are stress, hormonal shifts, nutritional gaps, and certain medications, and most causes are temporary and reversible once you identify the trigger.
How the Hair Growth Cycle Works
Your hair doesn’t grow continuously. Each follicle cycles through a growth phase, a brief regression phase, a resting phase, and finally a shedding phase. The growth phase lasts two to six years for scalp hair, which is why head hair can get so long compared to body hair. The resting phase lasts two to four months, during which the hair strand sits idle in the follicle before eventually releasing. At any given time, most of your follicles are in the growth phase while a small percentage are resting or shedding. That natural turnover is what accounts for those 50 to 150 daily hairs you find on your brush or in the drain.
Problems start when something forces a large batch of follicles out of the growth phase and into the resting phase simultaneously. Two to three months later, all of those hairs shed at once, and what was a barely noticeable daily loss suddenly becomes alarming handfuls.
Stress-Related Shedding
The most common type of sudden, widespread shedding is called telogen effluvium. It happens when a physical or emotional stressor shocks your system and pushes a disproportionate number of follicles into the resting phase at the same time. Because those follicles still need two to three months to complete the resting cycle before the hair actually falls out, the shedding always shows up well after the triggering event. This delay is why so many people can’t connect the dots on their own.
Known triggers include high fever, severe infections, major surgery, childbirth, psychological stress, crash diets low in protein, and sudden hormonal changes like stopping birth control pills. The acute form typically resolves on its own within six months once the stressor passes. If shedding continues beyond that window, a longer-lasting form may be at play, and it’s worth investigating whether an ongoing condition is keeping your body in a stressed state.
Hormonal Causes
Thyroid Problems
Both an overactive thyroid and an underactive thyroid can cause excessive shedding. Your thyroid hormones help regulate the metabolism of nearly every cell in your body, including hair follicle cells. When production is too high or too low, follicles can stop cycling properly and shift into the resting phase prematurely. The shedding tends to be diffuse, meaning it thins evenly across the scalp rather than creating bald patches. Other signs of a thyroid issue, like unexplained weight changes, fatigue, feeling unusually cold or warm, or changes in your skin texture, often accompany the hair loss.
Postpartum Shedding
During pregnancy, elevated estrogen levels extend the growth phase of your hair. This is why many pregnant women notice thicker, fuller hair. After delivery, estrogen drops back to normal levels, and all those follicles that were held in the growth phase enter the shedding phase at once. The result is dramatic hair loss that typically begins about three months after giving birth. It looks alarming, but it’s your body releasing hair that would have shed gradually over the previous nine months. For most women, normal hair density returns within six to twelve months without any treatment.
Nutritional Deficiencies
Iron is the nutrient most closely linked to hair shedding, and you don’t need to be anemic for low iron to affect your hair. Ferritin, the protein that stores iron in your body, needs to reach a certain level for follicles to function optimally. Research categorizes ferritin below 12 ng/mL as true iron deficiency, 13 to 20 ng/mL as iron depletion, and 21 to 70 ng/mL as technically adequate but still too low for a normal hair cycle. Levels at or above 70 ng/mL are considered sufficient for healthy hair growth. Many people, especially women with heavy periods or those following restrictive diets, fall into that middle range where standard blood tests come back “normal” but their hair is starving for iron.
Protein is another essential building block. Hair is made almost entirely of a protein called keratin, and when your diet doesn’t supply enough, your body triages protein toward vital organs and away from hair production. Crash diets and very low-calorie eating patterns are a well-documented trigger for shedding. Vitamin D also plays a role in hair follicle cycling. The receptors for vitamin D sit in the outer layer of the hair follicle, and without them, follicles lose the ability to initiate new growth cycles. Ensuring adequate vitamin D intake supports the environment your follicles need to keep turning over.
Medications That Cause Shedding
Several common drug classes list hair shedding as a side effect. Blood thinners like heparin and warfarin are known culprits. Certain blood pressure medications, including some beta-blockers and ACE inhibitors, have been associated with hair loss in a small percentage of users. Retinoids (used for acne and skin conditions), some antidepressants, mood stabilizers, antifungal medications, and even over-the-counter anti-inflammatory drugs can trigger shedding in susceptible people. The mechanism is the same as other forms of telogen effluvium: the medication pushes follicles into the resting phase, and shedding appears weeks to months after starting the drug. If you notice increased shedding after beginning a new medication, that timing is an important clue.
Scalp Conditions
Inflammation on the scalp itself can drive hair loss. Seborrheic dermatitis, the condition behind persistent dandruff, is a common example. Excess oil production irritates and inflames the scalp, which triggers intense itching. Repeated scratching physically damages hair follicles and disrupts normal growth. On top of that, the excess oil creates an environment where a naturally occurring yeast on your skin can overgrow, causing further inflammation and follicle damage. Treating the underlying scalp condition, usually with medicated shampoos or topical treatments, often stops the shedding and allows regrowth.
How to Tell If Your Shedding Is Excessive
Counting individual hairs is impractical, but there are simpler ways to gauge whether your shedding is outside the normal range. One method dermatologists use in the office is a pull test: grasping a small section of about 60 hairs near the scalp and pulling gently. In a person with normal shedding, two or fewer hairs come out. If significantly more release, that suggests active excessive shedding. You can approximate this at home, though it’s not as precise as a clinical assessment.
Pay attention to patterns over time rather than individual days. Finding more hair in your brush after washing is normal, since washing dislodges hairs that were already in the shedding phase. But if you’re consistently seeing noticeably more hair on your clothes, your pillow, or gathering at the shower drain over a period of weeks, and especially if you can see thinning or wider parting lines, that’s a sign worth investigating.
What Helps Hair Grow Back
The encouraging reality is that most shedding caused by telogen effluvium is fully reversible. Once the triggering stressor resolves, follicles re-enter the growth phase and new hair begins to emerge. The frustrating part is the timeline: because hair only grows about half an inch per month, it can take six months to a year before you notice meaningful regrowth and fullness returning.
In the meantime, the most productive steps are identifying and addressing whatever caused the shedding. If you’ve been through a stressful period, the shedding will typically wind down on its own. If you suspect a nutritional issue, getting your ferritin and vitamin D levels checked gives you concrete numbers to work with. For thyroid-related shedding, managing the thyroid condition usually restores normal hair cycling. If a medication is the likely trigger, your prescriber may be able to adjust the dose or switch to an alternative.
Gentle handling matters while your hair recovers. Avoid tight hairstyles that pull on the follicle, minimize heat styling, and skip chemical treatments until shedding stabilizes. These won’t speed up regrowth, but they prevent additional mechanical damage to hair that’s already fragile.