Hair shedding is a normal part of how your body continuously replaces old strands with new ones. Most people lose somewhere between 50 and 100 hairs a day without ever noticing, because new hairs are growing in at roughly the same rate. When shedding becomes visible, finding clumps in your shower drain or on your pillow, it usually means something has pushed more of your hair into its resting phase at once. That’s almost always temporary.
How the Hair Growth Cycle Works
Every strand on your head moves through four phases independently of the others. The growth phase lasts two to eight years and is when the strand actively lengthens. After that, a brief two-week transition phase signals the follicle to stop producing new cells. The strand then enters a resting phase lasting two to three months, during which it stays loosely anchored in the follicle but is no longer growing. Finally, the shedding phase releases that strand so a new one can take its place.
At any given time, roughly 85 to 90 percent of your hair is in the growth phase. Because each follicle cycles on its own schedule, you shed a little every day rather than all at once. When something disrupts that balance and forces a large percentage of hairs into the resting phase simultaneously, you get a noticeable wave of shedding a few months later, once those resting hairs reach the release point.
Shedding vs. Permanent Hair Loss
These two things look similar but work differently. Shedding means old hairs are falling out to make room for new growth. The follicle is still healthy and will produce a replacement strand. Permanent hair loss means the follicle itself has been damaged or has stopped producing hair entirely. You can sometimes tell the difference by looking at the fallen strand: shed hairs typically have a small white bulb at the root, showing they completed a full cycle. Broken hairs are shorter and snap off without a bulb.
Noticeable bald patches, a widening part line, or thinning that doesn’t fill back in over several months are signs that something beyond normal shedding may be happening. A dermatologist can determine whether your hair is shedding, breaking, or has stopped growing, which changes the approach to treatment entirely.
Common Triggers for Excessive Shedding
When shedding increases noticeably, it’s called telogen effluvium. This is a reactive process, meaning your body responds to some form of stress by shifting a large proportion of hair follicles into the resting phase at the same time. Under significant stress, up to 70 percent of growing hairs can shift into rest simultaneously, compared to the usual 10 to 15 percent.
The most common triggers include:
- Physical stress: high fever, severe infection, major surgery, or serious injury
- Hormonal shifts: postpartum changes, thyroid problems, stopping birth control or other estrogen-containing medications
- Nutritional deficiencies: low iron, low protein intake, or crash dieting
- Medications: blood pressure medications (beta-blockers), blood thinners, anti-seizure drugs, excess vitamin A, and some vaccinations
- Psychological stress: prolonged emotional distress or a major life event
Because the resting phase lasts two to three months, you typically won’t notice increased shedding until about three months after the triggering event. This delay often makes it hard to connect the shedding to its cause. If you suddenly find more hair in your brush, think back to what was happening in your life roughly three months earlier.
Postpartum Shedding
During pregnancy, elevated estrogen extends the growth 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 over” in the growth phase enters the resting phase at once. The result is a dramatic wave of shedding that typically begins about three months after giving birth.
This can look alarming. Handfuls of hair in the shower are common. But postpartum shedding usually resolves on its own within 6 to 12 months as the hair cycle resets. A balanced diet and gentle hair care can help minimize additional breakage during this period, but no product or supplement will stop the shedding itself. It simply has to run its course.
Nutritional Deficiencies That Cause Shedding
Hair follicles are metabolically active and sensitive to what you eat. Iron deficiency is the most common nutritional cause of hair shedding worldwide. It tends to produce chronic, diffuse thinning rather than patchy loss. Zinc deficiency can trigger shedding and make hair brittle. Low protein intake, especially from crash diets or restrictive eating, directly starves the follicle of the building blocks it needs.
Biotin deficiency, though less common, causes both skin rashes and hair thinning. Low vitamin D levels have been linked to more severe shedding in women. Even a severe deficiency in niacin (vitamin B3) or essential fatty acids (omega-3 and omega-6) can contribute to hair loss, though these are rarer in people eating a varied diet. The good news is that shedding caused by nutritional gaps is typically reversible once you correct the deficiency through diet or supplementation.
Seasonal Patterns Are Real
If you notice more hair falling out in late summer or early fall, you’re not imagining it. A study of over 800 women found that hair shedding follows an annual cycle, with the highest proportion of resting hairs occurring in summer. A smaller, less pronounced peak also appears in spring, while shedding rates are lowest in late winter. This seasonal rhythm means you might lose noticeably more hair for a few weeks each year without anything being wrong.
A Simple Self-Check
Dermatologists use a version of this in the office, and you can try a rough version at home. Grab a small cluster of about 50 to 60 hairs between your fingers, close to the scalp. Pull gently but firmly from root to tip. If more than five or six hairs come out easily, that suggests active, above-normal shedding. Try it in a few different areas of your scalp. For the most accurate result, don’t wash your hair for at least 24 hours before testing.
This won’t tell you the cause, but it can help you gauge whether what you’re experiencing is within normal range or worth investigating further.
How Long Recovery Takes
The shedding phase of telogen effluvium typically lasts three to six months. Once the underlying trigger is resolved, whether that’s recovering from an illness, adjusting a medication, or correcting a nutritional deficiency, most people see new growth filling in within six to eight months without any treatment. The new hairs will be shorter at first, which can create a slightly uneven texture as they catch up to the rest of your hair.
If shedding persists beyond six months with no clear trigger, or if you notice that regrowth isn’t happening, it may point to a chronic form of the condition or an ongoing issue like an undiagnosed thyroid problem or sustained nutritional deficit. In those cases, identifying and addressing the root cause is what restarts normal growth.