Losing between 50 and 150 hairs a day is normal for everyone, including men. If you’re suddenly finding clumps in the shower drain or noticing hair all over your pillow, something has likely shifted your hair cycle. The most common culprits are stress-related shedding, the early stages of male pattern hair loss, nutritional gaps, thyroid problems, or a medication side effect.
How Normal Shedding Works
Your hair grows in cycles. Each strand spends years in an active growing phase, then transitions into a resting phase that lasts a few months before the hair falls out and a new one replaces it. At any given time, about 10 to 15 percent of your hair is in that resting phase, which is why losing up to 150 strands a day is completely routine. You probably never noticed it before because new hairs were replacing them at the same rate.
When shedding becomes a problem, it’s because something has pushed a much larger percentage of your hair into the resting phase all at once. Instead of 10 to 15 percent, up to 70 percent of your growing hairs can shift into rest mode under significant stress. That’s when you start seeing hair everywhere.
Stress-Related Shedding
The most common cause of sudden, dramatic hair loss in men who aren’t going bald is a condition called telogen effluvium. It happens when a physical or emotional stressor forces a large wave of hair follicles out of their growing phase prematurely. The tricky part: the shedding doesn’t start right away. It typically shows up two to three months after the triggering event, which makes it hard to connect cause and effect.
Common triggers include:
- High fever or serious illness (including COVID-19)
- Major surgery or physical trauma
- Significant emotional stress (job loss, divorce, grief)
- Rapid weight loss or crash dieting
- Hormonal changes
If you look at the hairs you’re shedding, you’ll often see a small white bulb at the root end. That white bulb is the hallmark of a hair that completed its resting phase and released naturally from the follicle. It does not mean the follicle is damaged or dead. Once the underlying stressor resolves, hair typically starts regrowing within three to six months. Full recovery can take up to a year, but the hair does come back.
Male Pattern Hair Loss
If your shedding has been gradual rather than sudden, and you’re noticing thinning at the temples, crown, or hairline, the cause is more likely male pattern hair loss. This affects roughly half of all men by age 50 and is driven by genetics and hormones, not stress.
The key player is a hormone called DHT, which your body converts from testosterone. DHT binds to receptors in your scalp follicles with about five times the strength of regular testosterone. Over time, it causes follicles to shrink in a process called miniaturization. Each hair growth cycle produces a thinner, shorter, weaker strand until the follicle eventually stops producing visible hair altogether.
This type of loss feels different from stress shedding. You may notice periods of increased shedding (especially while washing or combing), but the real sign is that the hair growing back is finer and shorter than before. The pattern is predictable: receding at the temples, thinning at the crown, or both. Unlike stress-related shedding, male pattern hair loss is progressive and won’t reverse on its own.
Low Iron and Vitamin D
Nutritional deficiencies are an underappreciated cause of hair shedding in men, partly because men don’t think of themselves as likely to be deficient. But research tells a different story. In one study comparing people with diffuse hair loss to healthy controls, the hair loss group had significantly lower iron stores (ferritin levels averaging around 15 ng/ml compared to 25 ng/ml in healthy individuals) and lower vitamin D levels (averaging 14 ng/ml versus 17 ng/ml in healthy people, with the normal range starting at 20 ng/ml).
Iron is essential for the rapidly dividing cells in your hair follicles, and vitamin D plays a role in cycling follicles from rest back into active growth. If you’ve been eating poorly, restricting calories, or simply not getting much sun, these levels can drop enough to affect your hair without causing any other obvious symptoms. A simple blood test can check both.
Thyroid Problems
Your thyroid gland controls metabolism throughout your body, including in your hair follicles. Both an underactive and overactive thyroid can trigger widespread shedding. About 33 percent of people with hypothyroidism and 50 percent of people with hyperthyroidism experience hair loss.
The two conditions affect hair differently. An underactive thyroid slows everything down: hair grows slowly and becomes coarse, dry, and brittle. You might also lose the outer third of your eyebrows. An overactive thyroid does the opposite, making hair fine and silky but weaker, with reduced tensile strength that leads to breakage and shedding. Either way, the shedding is diffuse (all over the scalp, not in patches) and reversible once thyroid levels are corrected.
Medications That Cause Shedding
Several common medications can trigger hair shedding as a side effect. The most frequently linked drug classes are beta-blockers (used for high blood pressure and anxiety), retinoids (including high-dose vitamin A supplements), blood thinners, certain anti-seizure medications, and some thyroid drugs. Even immunizations have been associated with temporary shedding in rare cases.
Medication-related shedding follows the same delayed pattern as stress shedding, typically appearing weeks to months after starting the drug. The good news is that hair growth generally restarts after the medication is stopped or switched. If you started a new prescription in the months before your shedding began, that’s worth flagging.
Scalp Conditions
An itchy, flaky scalp can contribute to shedding, though the mechanism is different. Seborrheic dermatitis, a common condition caused by an overgrowth of a yeast that naturally lives on your skin, creates inflammation, flaking, and itching. The hair loss comes primarily from scratching, which damages strands and pulls them out prematurely. It’s not permanent hair loss, but it can be persistent if the underlying scalp condition isn’t treated. Over-the-counter medicated shampoos containing zinc or antifungal ingredients are the typical first step.
How to Tell What’s Causing Your Shedding
A few clues can help you narrow down the cause before you see anyone about it. First, look at the pattern. Diffuse thinning all over the scalp points toward stress shedding, nutritional issues, or thyroid problems. Thinning concentrated at the temples and crown suggests male pattern hair loss. Patchy loss in distinct spots is a different category entirely (alopecia areata, an autoimmune condition).
Next, think about timing. If you can trace the shedding back to a stressful event, illness, surgery, or new medication two to three months prior, stress-related shedding is the most likely explanation. If the thinning has been creeping in over months or years, male pattern loss is more probable.
You can also do a rough version of what clinicians call a hair pull test. Grab a small cluster of about 50 to 60 hairs between your fingers and pull gently from root to tip. If more than five or six hairs come out easily, that’s considered a sign of active, abnormal shedding. Try this in several spots on your scalp. Just make sure you haven’t washed your hair in the previous 24 hours, since washing removes loose hairs and can skew the result.
Finally, examine the shed hairs themselves. A white bulb at the root means the hair completed its resting phase and shed naturally, which is typical of stress-related shedding. If hairs are breaking mid-shaft without a bulb, that points more toward damage, whether from a scalp condition, nutritional deficiency, or physical stress on the hair.