Why Is My Hair Falling Out? Common Causes of Hair Loss

Hair loss affects millions of people at some point in their lives. If you’ve noticed more hair in your brush, the shower drain, or on your pillow, you may be wondering, Why is my hair falling out? It can feel concerning, but in many cases, hair shedding is normal and temporary. Learning about the causes of hair loss can help you understand if what you’re experiencing is part of the natural hair cycle or something that may need medical attention.

In many cases, hair loss can be managed or treated once the cause is identified. From genetics and stress to hormonal changes and nutritional deficiencies, several factors can contribute to thinning hair or sudden shedding. Let’s take a closer look at the most common causes of hair shedding and when it may be time to seek professional guidance.

How Much Hair Loss Is Normal?

Before becoming too worried, it's helpful to understand what is considered “normal”. Most people lose 50 to 100 hairs per day. Because the human scalp contains roughly 100,000 hair follicles, shedding this amount is typically not noticeable.

Hair growth occurs in a natural cycle that includes three main phases: a growth phase called anagen, a transition phase called catagen, and a resting phase called telogen. 

The anagen phase is known as the active growth stage when hair grows continuously from the follicle. This phase lasts anywhere from two to six years, and about 85–90% of the hair on your head is in this stage. 

Next is the catagen phase, a short transition period lasting only a few weeks that signals that active growth is coming to an end. Finally, hair enters the telogen phase, also known as the resting phase. During this time, the hair follicle rests before the hair sheds and new growth begins, restarting the cycle.

When something disrupts this cycle, like illness, stress, or hormonal shifts, you may notice increased shedding or thinning. Understanding this cycle can help explain why sudden hair loss may occur even months after a triggering event.

Genetics and Pattern Hair Loss

One of the most common causes of hair loss is genetics. Known medically as androgenetic alopecia, this type of hair loss is often referred to as pattern hair loss.

Male Pattern Baldness

In men, pattern hair loss typically begins with a receding hairline or thinning at the crown. Over time, these areas may expand, eventually leading to partial or complete baldness. This type of hair loss is influenced by both genetics and hormones. Specifically, dihydrotestosterone (DHT), which can shrink hair follicles over time.

Female Pattern Hair Loss

Women can also experience genetic hair thinning, though it often appears differently. Instead of a receding hairline, women usually notice gradual thinning along the part line or at the crown of the head. Female pattern hair loss often progresses slowly and may become more noticeable with age.

While genetic hair loss cannot always be completely reversed, some treatments can help slow progression and improve hair density.

Stress and Temporary Hair Loss

If you have experienced sudden hair loss, stress may be a contributing factor. A condition called telogen effluvium occurs when a large number of hair follicles enter the resting phase at the same time. This leads to noticeable shedding several weeks or months after a stressful event.

Common triggers can include: major illness or infection, surgery or hospitalization, significant emotional stress, rapid weight loss, and high fever.

Telogen effluvium can feel worrisome, but it is often temporary. Once the underlying trigger is resolved, hair growth typically resumes over the following months.

Hormonal Changes

Hormonal fluctuations are another common reason people ask, “Why is my hair falling out?” Different life stages and medical conditions can disrupt hormonal balance and affect the hair growth cycle.

Pregnancy and Postpartum Hair Loss

During pregnancy, it is common for women to have fabulous hair. The increased estrogen levels often make hair appear thicker and fuller. After childbirth, hormone levels shift dramatically, which can lead to increased shedding. Postpartum hair loss is common and typically resolves within several months.

Menopause

Women experience hormone fluctuation during menopause. These hormonal changes contribute to hair thinning in women. Reduced estrogen levels can affect hair density and growth patterns.

Thyroid Disorders

Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid) can lead to hair thinning or shedding. Treating the underlying thyroid condition often helps restore normal hair growth.

Nutritional Deficiencies

Just like the rest of your body, your hair follicles rely on proper nutrition to grow and stay healthy. When your body is lacking certain nutrients, it can affect how well your hair grows. Consequently, hair may become thinner, more brittle, or shed more than usual. In some cases, nutritional deficiencies can disrupt the normal hair growth cycle and lead to noticeable hair loss.

One common nutritional cause of hair loss is iron deficiency, which is especially common in women. Iron plays an important role in helping red blood cells carry oxygen throughout the body, including to your hair follicles. Without enough iron, follicles may not receive the oxygen they need to support healthy hair growth.

Another important factor is protein intake. Hair is primarily made of a protein called keratin, so when the body doesn’t get enough protein through diet, it may affect the strength and growth of hair. This can lead to increased shedding or slower hair growth.

Certain vitamin deficiencies can also contribute to hair thinning. Nutrients such as vitamin D, vitamin B12, and biotin support healthy hair follicles and the hair growth cycle. When levels of these vitamins are low, hair may appear weaker or thinner over time.

Eating a balanced diet that includes adequate protein, vitamins, and minerals is one of the best ways to support overall hair health. While nutrition is only one factor in hair growth, maintaining good dietary habits can help provide your hair follicles with the nutrients they need to grow strong, healthy hair.

Hair Loss and GLP-1 Weight Loss Medications

Recently, some people have reported increased hair shedding while taking GLP-1 medications, such as semaglutide (Ozempic® or Wegovy®) or tirzepatide (Mounjaro® or Zepbound®). These medications are commonly prescribed for diabetes and weight management and have become increasingly popular in recent years.

Current research suggests that these medications do not directly cause hair loss. Instead, hair shedding may occur as a result of rapid weight loss, which can place temporary stress on the body. When the body experiences sudden weight loss, it may shift more hair follicles into the resting phase of the hair cycle. This condition, known as telogen effluvium, often leads to increased shedding several weeks or months after the triggering event.

Rapid weight loss may also lead to temporary nutritional deficiencies, particularly if calorie intake is significantly reduced. Nutrients like protein, iron, and certain vitamins are essential for healthy hair growth, and when the body is not receiving enough of them, hair shedding may increase.

The encouraging news is that this type of hair loss is typically temporary. As weight stabilizes and nutritional intake improves, hair growth usually returns to its normal cycle. 

If you are experiencing significant hair shedding while taking a GLP-1 medication, discussing your symptoms with your healthcare provider or dermatologist can help determine the best next steps.

Medical Conditions and Medications

Certain medical conditions and medications may also cause hair loss. In some cases, hair shedding occurs as a side effect of treatment or as a symptom of an underlying health issue.

Conditions associated with hair loss may include:

• Autoimmune disorders such as alopecia areata
• Scalp infections
• Chronic illnesses

Additionally, some medications, such as those used to treat high blood pressure, depression, cancer, or arthritis, may contribute to hair thinning. If hair loss begins after starting a new medication, discuss this with your healthcare provider.

When Should You See a Dermatologist for Hair Loss?

Occasional shedding is normal, but certain signs may indicate that it’s time to consult a professional. You may want to see a dermatologist if you experience:

• Sudden or excessive hair loss
• Patchy hair loss or bald spots
• Hair loss accompanied by scalp pain or itching
• Thinning that continues to worsen over time

A dermatologist can evaluate your scalp, review your medical history, and recommend appropriate tests if needed. Identifying the cause of hair loss early can help guide effective treatment options.

Understanding the causes of hair loss is the first step toward finding the right solution. While some shedding is completely normal, persistent or sudden hair loss may signal an underlying issue that deserves attention. If you’re concerned about changes in your hair, consulting one of our expert dermatologists at Draper Dermatology can help you determine the cause and explore effective treatment options.