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Diagnosing Hair Loss

NYU Langone dermatologists are experienced in recognizing the signs of hair loss, whether the cause is genetic, medical, or environmental. They visually assess the pattern of hair loss to ascertain the type of hair loss and confirm diagnosis by using advanced techniques, including a computerized measurement tool that magnifies the scalp’s appearance by up to 100 times.

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If your doctor suspects that an underlying medical condition may be the cause of hair loss, a blood test or scalp biopsy may be recommended. All of these diagnostic tests can be conducted in your dermatologist’s office.

Medical History

To determine the cause of hair loss, your dermatologist asks a variety of questions about when hair loss began, what the patterns of hair loss are, what kind of hairstyles you usually wear, whether hair loss runs in your family, and other details about your symptoms. He or she may ask about any other medical conditions you have.

Details that may seem unrelated—such as what foods you eat or whether you recently gave birth—may provide a clue about the cause of the hair loss.

Physical Exam

A dermatologist examines your scalp to check for inflammation, redness, sores, or scarring. The doctor looks closely at your hair to determine how much is being lost, the pattern of the hair loss, and whether there is hair breakage.

During a physical exam, your doctor may perform simple tests to learn more about the health of your hair. These may include the following.

Pull Test and Tug Test

This simple test measures the severity of hair loss. During a pull test, a dermatologist grasps small sections of hair, about 40 strands, from different parts of the scalp and gently tugs. If six or more strands fall out, you have what’s known as active hair loss.

This may mean you have one of the following types of hair loss: telogen effluvium, in which hair falls out all over the scalp due to an interruption in the body’s cycle of hair production; anagen effluvium, or rapid hair loss resulting from medical treatment; loose anagen syndrome, which most commonly develops in young children and occurs when hair that is not firmly rooted in the follicle; early androgenetic alopecia, better known as “male pattern hair loss” or “female pattern hair loss”; or advanced alopecia areata, an autoimmune disease in which the body’s immune system attacks healthy tissues, including the hair follicles.

During a tug test, the doctor grasps a section of hair and holds it with two hands, one near the root and one near the tip, then tugs to see if any of the strands break in the middle. This test gives the dermatologist information about the brittleness or fragility of your hair strands.

A doctor may use the tug test when he or she suspects a hair shaft abnormality, which causes hair strands to thin, weaken, and possibly break.

Card Test

A dermatologist uses a card test to examine the health of hair shafts and to evaluate the number of new hair strands that are growing. The procedure is simple: The dermatologist creates a part in the hair and holds a small rectangular card covered in felt against a section of the scalp. The color of the felt should contrast with the color of the hair. New hair strands, even very small or broken ones, in this area are visible against the felt card and can be counted and examined.

Very thin strands may signal that you have telogen effluvium, whereas short strands with broken tips may indicate a hair shaft abnormality.

Trichometric Analysis

In certain instances, dermatologists at NYU Langone use trichometric analysis, a sophisticated computerized measurement tool, to analyze characteristics of the scalp and hair. Our doctors use a digital assessment system called Folliscope® which consists of a small handheld device containing a high definition, microscopic camera.

Doctors use this camera to take pictures of the scalp and hair, and the images are displayed on a computer monitor. The Folliscope® can magnify these images by up to 100 times, giving doctors a detailed look at hair, hair follicles, and the scalp.

The Folliscope® also provides information about hair coverage, including the total number of hairs on the scalp and the diameter of each strand of hair. These details are used to monitor the progression of new hair growth after treatment begins.

Fungal Culture

A fungal culture is a laboratory test that can confirm the presence of a fungus in hair or scalp cells. A dermatologist may recommend this test to determine whether a fungal infection called tinea capitis, or scalp ringworm, is the cause of hair loss.

A dermatologist may scrape or swab the scalp or take a small sample of skin or hair for laboratory testing. It can take several weeks of incubation in the laboratory for a fungus culture to become positive.

Punch Biopsy

Most of the time, dermatologists are able to determine the cause of hair loss during a physical examination and trichometric analysis. If more information about the hair follicle or scalp is needed to refine a diagnosis—for example, if there are lesions on the scalp that could be caused by more than one form of hair loss—your doctor may perform a scalp biopsy.

It’s called a “punch” biopsy because of the technique used: Dermatologists use a device the size and shape of a pencil to puncture the scalp and remove a small tissue sample. This sample is sent to a lab for testing, and the incision is closed with a few stitches. Biopsies are frequently used to distinguish between the types of cicatricial, or scarring, alopecia.

Blood Tests

If doctors suspect the hair loss may be due to an underlying medical condition, a vitamin or mineral deficiency, or a hormonal imbalance, they may recommend one or more blood tests. For example, it may appear that a woman whose hair is thinning all over the scalp has hereditary hair loss, but it’s possible that the cause is actually an iron deficiency.

Iron Deficiency

Too little iron in the bloodstream may contribute to hair loss. Doctors use blood tests to check the level of ferritin, a protein that indicates how much iron is stored in the body. Ferritin levels are often low in menstruating women; those with anemia, a condition in which people lack healthy red blood cells; and vegetarians or vegans.

Adding foods rich in iron to your diet may help hair to regrow. These include dark, leafy greens, red meat, whole grains, and legumes. Iron supplements, which are used to treat anemia, may also help to stop hair loss.

Thyroid Disease

Hair loss may be a sign of a thyroid disease such as hyperthyroidism or hypothyroidism. These conditions cause the thyroid gland to overproduce or underproduce certain hormones that regulate the body’s metabolism. The link between thyroid disease and hair loss is unclear, but there is some evidence that thyroid disease may cause the body to produce hormones that destroy hair follicles.

If you’ve recently noticed a dramatic change in your weight without changing your diet, fatigue, or sudden muscle weakness, doctors may recommend a blood test to determine the level of a hormone called thyroid-stimulating hormone, or TSH. TSH levels are closely related to thyroid function, and unusually high or low levels may confirm or eliminate a diagnosis of thyroid disease.

Androgen Excess

Women who have thin hair with no bald patches may have a hormonal imbalance caused by excess levels of androgens, a class of hormones that includes testosterone. Signs of androgen excess include hair loss and baldness; hair growth on the face, chest, or abdomen; and irregular menstrual periods and acne. A blood test can reveal an elevated androgen level.  


Dermatologists use digital photography to track the progress of your treatment. Your doctor may take photos from many angles during your first visit and compare them to photos taken during follow-up appointments.

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