The most likely reason you’re going bald is androgenetic alopecia, commonly called pattern hair loss. It affects roughly 30% of men by their 30s and up to 80% of men by age 70. About half of women develop it by 70 as well, though it looks different. Your genetics determine how sensitive your hair follicles are to a hormone called DHT, and that sensitivity is the single biggest driver of progressive balding. But genetics aren’t the only possibility. Stress, nutritional gaps, and medical conditions can all trigger hair loss that looks and feels quite different from pattern baldness.
How DHT Shrinks Your Hair Follicles
Your body converts testosterone into a more potent hormone called DHT. In people genetically prone to hair loss, DHT binds to receptors inside hair follicles on the top and front of the scalp. Once activated, these receptors essentially tell the follicle to shrink. Over successive growth cycles, each hair comes back thinner, finer, and shorter until the follicle eventually produces nothing visible at all. This process is called miniaturization, and it’s why balding tends to be gradual rather than sudden.
Every hair on your head cycles through three phases: a growth phase lasting 3 to 10 years, a brief transition phase of 2 to 3 weeks, and a resting phase of 3 to 4 months before the hair falls out and a new one begins growing. Each follicle goes through this full cycle 10 to 20 times in a lifetime. DHT shortens the growth phase with each cycle, so hairs spend less and less time growing and more time resting. At any given moment, about 15% of your hair is in the resting phase. When that percentage climbs, thinning becomes noticeable.
Pattern Baldness in Men vs. Women
In men, pattern hair loss follows a recognizable progression measured on the Norwood scale. It typically starts at the temples, creating an M-shaped hairline that recedes 1 to 2 centimeters from its original position. By the time you notice deep recession at the temples and thinning at the crown, you’re in the moderate stages. Eventually, the two thinning zones merge, leaving only a horseshoe-shaped band of hair around the sides and back of the head. About 25% of men show noticeable temple recession by age 30.
Women lose hair differently. Rather than a receding hairline, female pattern hair loss shows up as diffuse thinning across the top of the scalp while the front hairline stays intact. This is measured on the Ludwig scale across three grades of severity. Because the thinning is spread out rather than concentrated, many women notice it first when their part looks wider or their ponytail feels thinner.
Stress and Sudden Shedding
If your hair loss came on quickly rather than gradually, the cause may not be genetic at all. Telogen effluvium is a type of temporary hair loss triggered by a shock to your system. Common triggers include high fever, severe infections, major surgery, childbirth, crash diets low in protein, thyroid problems, stopping birth control pills, and significant psychological stress.
The timeline is distinctive: hair shedding typically starts two to three months after the triggering event. That delay makes it tricky to connect cause and effect. You might not immediately link a bad illness in January to handfuls of hair in the shower in March. Acute telogen effluvium usually resolves within six months once the trigger is removed, and the hair grows back on its own.
Nutritional Deficiencies That Cause Hair Loss
Low iron is one of the most well-documented nutritional causes. While most labs flag ferritin (your stored iron) as “normal” above 15 to 30 ng/mL, hair specialists use a higher threshold. Levels below 30 ng/mL are highly likely to contribute to hair loss, and optimal hair growth generally requires levels above 70 ng/mL. If you’re in the 30 to 40 range, your iron stores may technically be normal but still too low to support healthy hair.
People experiencing hair loss also tend to have lower vitamin D levels compared to those without hair loss. Zinc plays a role too, though documented zinc deficiency is uncommon in people eating varied diets. Supplementing these nutrients only helps if you’re actually deficient. Taking hair growth vitamins when your levels are already adequate won’t make a difference, and medical reviews consistently find insufficient evidence to recommend supplements without a documented deficiency.
Autoimmune Hair Loss
Alopecia areata is a distinct condition where your immune system attacks hair follicles directly, causing smooth, round patches of hair loss that can appear on the scalp, beard, eyebrows, or anywhere on the body. It’s not driven by DHT and doesn’t follow the gradual pattern of androgenetic alopecia. In severe cases, it can progress to total scalp or body hair loss.
Treatment for severe alopecia areata has changed significantly in recent years. The FDA has approved several medications that work by blocking specific immune signals responsible for the attack on follicles. Baricitinib was approved in 2022, ritlecitinib in 2023 for adults and adolescents 12 and older, and deuruxolitinib more recently. These are prescription oral medications for severe cases, not over-the-counter options for typical balding.
How Hair Loss Is Diagnosed
A dermatologist can usually identify the type of hair loss through a physical exam and your medical history. One common test involves grasping about 40 strands of hair and gently tugging. If six or more strands come out, that indicates active hair loss rather than normal shedding. The doctor will also look at where thinning is occurring and whether the pattern matches genetic hair loss or something else.
If the cause isn’t clear from the exam, blood work can check for iron, thyroid function, vitamin D, and hormonal imbalances. A scalp biopsy, where a small sample of skin is removed and examined under a microscope, is occasionally needed. Biopsies are most useful for distinguishing between types of scarring hair loss, where the follicle is permanently destroyed, and non-scarring types where regrowth is still possible.
What Actually Works for Pattern Baldness
The two most studied treatments for androgenetic alopecia are minoxidil (a topical liquid or foam applied to the scalp) and finasteride (an oral pill that reduces DHT levels). Minoxidil is available over the counter; finasteride requires a prescription.
In a study of men using 5% minoxidil, 74.2% reported improved hair density after four months, while 24.3% saw no change and only 1.5% reported worsening. After a full year, investigators rated the treatment very effective in about 16% of patients, effective in 48%, moderately effective in 21%, and ineffective in roughly 16%. One concrete measure: the average number of hairs lost during washing dropped from about 70 at the start of the study to 34 by the end.
The key with either treatment is timing. They work best at slowing loss and regrowing hair in areas where follicles are miniaturized but not yet dead. Once a follicle has been dormant for years, topical treatments are unlikely to revive it. Starting earlier typically produces better results than waiting until significant balding has occurred.
Hats, Shampooing, and Other Myths
Wearing a hat does not cause baldness. A study of 92 identical male twins found that men who wore hats daily actually experienced less hair loss at the temples than their non-hat-wearing twins. A separate study of 98 identical female twins found that not wearing hats was associated with more hair loss, possibly because hats protect hair from sun damage. The only caveat is that extremely tight or hot headwear could theoretically reduce blood flow to follicles and create tension, but normal hat use is not a concern.
Frequent shampooing doesn’t cause hair loss either. The hairs you see in the drain were already in the resting phase and ready to fall out. Washing simply dislodges them sooner than they would have fallen on their own. If you skip a few days of washing, you’ll notice more hair in the shower the next time, but that’s accumulation, not acceleration.