Testing for alopecia involves a combination of physical examination, scalp imaging, blood work, and sometimes a small skin biopsy. No single test diagnoses every type of hair loss, so the process typically starts with simple hands-on checks and narrows down from there based on what your doctor observes. Here’s what to expect at each stage.
What Your Doctor Asks First
Before any physical test, a thorough medical history does much of the diagnostic work. Your doctor will want to know when you first noticed thinning or shedding, whether it came on gradually or suddenly, and whether anyone in your family has hair loss or autoimmune conditions. Medications, recent surgeries, major life stressors, crash diets, and recent illnesses all matter because they can trigger specific types of hair loss. Women may be asked about menstrual changes or hormonal shifts. This conversation shapes which tests come next.
The Hair Pull Test
This is the most basic bedside test for active hair loss. Your dermatologist grasps a small group of about 50 to 60 hairs between the thumb, index, and middle fingers, then gently tugs from the scalp outward toward the ends. If more than five or six hairs come out easily, the test is considered positive, meaning you have active shedding. The test is repeated across several areas of the scalp to see whether hair loss is widespread or concentrated in one zone.
For accurate results, you should avoid washing your hair for at least 24 hours before the appointment. Shampooing can remove loose hairs that would otherwise show up during the pull, making the test appear falsely normal.
Tracking Hair Loss at Home
If you want to monitor shedding between appointments, a method called the 60-second hair count gives you a simple baseline. Before shampooing, comb your hair for 60 seconds over a pillowcase or sheet that contrasts with your hair color. Start the comb at the back top of your scalp and move it forward. Count the hairs left in the comb and on the fabric, and write the number down. Repeat this before three consecutive shampoos, always using the same comb.
In a study of men aged 20 to 60, normal shedding during this test averaged about 10 hairs, with a range of 0 to 78. The widely repeated claim that losing 100 hairs a day is normal has never been well supported. Bringing your recorded counts to your dermatology visit gives your doctor real data to work with rather than relying on your impression of how much hair you’re losing.
Trichoscopy: Magnified Scalp Imaging
Trichoscopy uses a handheld magnifying device (a dermatoscope) to examine the scalp at high magnification without cutting or scraping anything. It’s painless and takes just a few minutes, but it reveals details invisible to the naked eye that help distinguish between types of hair loss.
For pattern hair loss (androgenetic alopecia), the most telling sign is hair diameter variability, found in over 94% of patients in one large review. This means thick, healthy hairs sit next to thin, miniaturized ones in the same area. Another strong marker is the peripilar sign, a subtle brown halo around the hair shaft, which has the highest specificity for pattern hair loss. Fine vellus hairs, tiny colorless strands replacing normal ones, appear in about two-thirds of cases.
For alopecia areata, the autoimmune type, trichoscopy reveals different clues. Yellow dots, first identified in 2006, are a hallmark. These are round, yellowish structures in the follicle openings that result from plugged, empty hair follicles. Exclamation mark hairs, short broken strands that taper toward the scalp, are another classic finding.
For traction alopecia, caused by tight hairstyles pulling on the hair over time, the key diagnostic feature is the fringe sign: a thin line of fine hairs remaining along the original hairline while the hair behind it has thinned or disappeared. Tenderness, stinging, and small acne-like bumps in the area of tension are also common. This type is usually diagnosed through clinical examination and dermoscopy alone.
Scarring vs. Non-Scarring Alopecia
One of the most important distinctions your doctor makes early on is whether your hair follicles are still intact. In non-scarring alopecia (pattern hair loss, alopecia areata, telogen effluvium), the follicle openings are preserved and hair can potentially regrow. In scarring (cicatricial) alopecia, the follicles are destroyed and replaced by scar tissue, making regrowth in those areas unlikely.
Scarring alopecia typically looks atrophic and shiny, with a visible loss of the tiny pores where hairs normally emerge. Inflammation may or may not be present. In one specific type called folliculitis decalvans, multiple hairs may emerge from a single opening, creating a “doll’s hair” tufting pattern. Identifying scarring alopecia early matters because treatment focuses on stopping further destruction rather than regrowing what’s already lost.
Blood Tests
Blood work helps rule out underlying medical conditions driving hair loss. The specific panel varies depending on your symptoms and history, but commonly includes thyroid function, iron stores, and sometimes hormone levels.
Iron status is particularly relevant. Standard lab ranges consider ferritin (your body’s iron storage protein) normal at 20 ng/mL or above, but research suggests hair follicles need more than that to function well. One study found that hair regrowth improved significantly when ferritin levels were above 40 ng/mL, and optimal hair growth was observed at levels around 70 ng/mL. If your ferritin is technically “normal” but sits in the low range, it may still be contributing to shedding.
Thyroid disorders, both overactive and underactive, can trigger a type of diffuse shedding called telogen effluvium, where large numbers of hairs shift into their resting phase and fall out simultaneously. Checking thyroid function with a simple blood draw can confirm or rule this out. Vitamin B12 levels may also be tested, with optimal levels for hair health falling between 300 and 1,000 ng/L.
Scalp Biopsy
When the diagnosis remains unclear after examination, trichoscopy, and blood work, a scalp biopsy provides definitive answers. This involves removing one or two small 4mm circles of skin (about the size of a pencil eraser) under local anesthesia. The procedure is quick and typically leaves a tiny scar hidden by surrounding hair.
Where the sample is taken from matters. For scarring alopecia, the biopsy should come from the edge of the affected area rather than the center, because the center may show only scar tissue without the active disease process that reveals the underlying cause. For non-scarring types like alopecia areata or pattern hair loss, the sample comes from within the thinning area itself.
How the tissue is sliced for examination also depends on the suspected diagnosis. For non-scarring hair loss, pathologists typically cut the sample horizontally, which lets them count hair follicles at different levels and assess miniaturization, the gradual shrinking of follicles that defines pattern hair loss. For scarring alopecia, one sample is cut horizontally and the other vertically, because certain inflammatory patterns sit at the junction between skin layers and can be missed in horizontal slices alone. The vertical view also lets the pathologist see the full thickness of skin in a single glance, which helps identify the specific type of scarring process at work.
Biopsy is especially valuable for distinguishing between conditions that look similar on the surface, such as alopecia areata versus early pattern hair loss, or between different types of scarring alopecia that require different treatment approaches.