Suspecting a cause and actually confirming one are two different things. Iron deficiency, thyroid dysfunction, a hormonal shift, straightforward female pattern hair loss — you might already have a guess after the last few posts, but a guess isn’t a diagnosis. A hair loss workup is what turns one into the other.

A good hair loss workup answers a more useful question than “am I losing hair“: what’s actually happening, and is there something treatable behind it? There isn’t one universal list of tests every woman needs — the right testing depends on whether you’re dealing with shedding, gradual thinning, breakage, a changing hairline, scalp symptoms, or some combination of those. That’s why I don’t think of a hair loss workup as ordering every possible lab. It’s about matching the testing to the story.

If you’re ready to stop guessing, you can schedule a personalized evaluation with Wible Wellness — we’ll review your symptoms, timeline, medications, hormones, nutrition, previous labs, and hair-loss pattern to figure out what testing actually makes sense for you.

The Standard Hair Loss Workup

A few tests come up again and again when a woman has unexplained diffuse hair loss.

CBC. A complete blood count is the basic starting point. It can identify anemia, which matters if you have heavy menstrual bleeding, a history of iron deficiency, restrictive eating, or another reason you might be losing or not replacing iron (Trost et al., Journal of the American Academy of Dermatology, 2006). A normal hemoglobin doesn’t automatically mean your iron stores are ideal, though — that’s one reason ferritin gets its own place in the evaluation.

Ferritin and iron studies. Ferritin tells us about stored iron; depending on the situation, a full iron panel might also include serum iron, TIBC or transferrin, and transferrin saturation (Trost et al., Journal of the American Academy of Dermatology, 2006). This is one of the more commonly ordered pieces of a hair loss workup, particularly when the pattern suggests telogen effluvium or there are risk factors for iron deficiency (Mirmirani & Fu, JAMA, 2021). Studies of women with diffuse hair loss have found associations with lower ferritin and iron deficiency, though the relationship isn’t as simple as one magic cutoff number — there’s no universally accepted ferritin level that guarantees optimal hair growth (Redler et al., Experimental Dermatology, 2017).

You’ll sometimes see 70 ng/mL cited online as the number every woman with hair loss needs. That figure comes from an older paper that proposed it as an “optimal” level, and it’s been picked up widely in integrative and functional medicine settings — but it isn’t a universally accepted medical threshold, and later research has produced mixed results (Redler et al., Experimental Dermatology, 2017; Trost et al., Journal of the American Academy of Dermatology, 2006). So rather than treating 70 as a magic number, I look at ferritin in context: symptoms, menstrual blood loss, diet, CBC, iron saturation, inflammation, and the overall hair-loss pattern.

TSH and free T4. Thyroid dysfunction can contribute to diffuse hair shedding, so thyroid testing gets considered whenever the cause isn’t obvious (Mirmirani & Fu, JAMA, 2021). For most people, TSH and free T4 provide the core assessment — free T4 shows the amount of circulating thyroid hormone available to your tissues. Free T3 is sometimes useful but not automatically necessary for every person with hair loss; the American Thyroid Association notes that T3 testing generally isn’t helpful for diagnosing hypothyroidism, since T3 often stays within the reference range in hypothyroidism and free T3 immunoassays are less reliable (Van Uytfanghe et al., Thyroid, 2023; Chaker & Papaleontiou, JAMA, 2025).

Thyroid antibodies. If your history or symptoms raise concern for autoimmune thyroid disease, antibodies — commonly TPO and thyroglobulin — can add another piece of the puzzle. They help identify autoimmune thyroid disease like Hashimoto’s, but they don’t tell us how well your thyroid is actually functioning; TSH and free T4 remain the primary measures of that. Thyroid antibodies aren’t something everyone with hair loss needs by default — they’re most useful when there’s a specific reason to suspect thyroid autoimmunity, and antibody positivity occurs in 5–20% of people without hypothyroidism (Chaker & Papaleontiou, JAMA, 2025).

The Add-On Panel: When More Testing Makes Sense

Once the basic hair loss workup is complete, additional testing should be driven by your history, not automatically added to everyone’s order.

Vitamin D is sometimes checked in women with diffuse hair loss, particularly when other deficiency risk factors are present. Research shows an association between lower vitamin D and some forms of nonscarring hair loss, but a low level isn’t automatically the explanation — if you’re deficient, correcting it is reasonable for overall health, though whether supplementation alone restores hair is a separate question (Drake et al., JAMA Dermatology, 2023; Redler et al., Experimental Dermatology, 2017).

Zinc plays a role in normal cellular growth, including the rapidly dividing cells in the hair follicle, and testing can make sense when dietary intake is limited, malabsorption is suspected, or other deficiency signs are present (Drake et al., JAMA Dermatology, 2023). This is also an area where more isn’t better — high-dose zinc without a documented reason can interfere with copper absorption and create a new problem (Fosmire, American Journal of Clinical Nutrition, 1990; Sandstead, American Journal of Clinical Nutrition, 1995).

Androgen testing isn’t necessary for every woman with female pattern hair loss. It becomes more useful with clues like irregular menstrual cycles, new or worsening facial hair, significant acne, rapid progression of thinning, or other signs suggestive of PCOS — testing might include total and/or free testosterone and DHEA-S. Importantly, female pattern hair loss can occur even when androgen levels are completely normal; the diagnosis is primarily clinical, and normal androgens don’t rule it out (Olsen, New England Journal of Medicine, 2025).

ANA and autoimmune testing can be appropriate when the history suggests an autoimmune condition — hair loss alongside certain rashes, joint symptoms, unexplained fevers, or photosensitivity, for example. It isn’t a good all-purpose screening test, though: positive ANA results occur in healthy people too, with population studies finding positivity in roughly 15% of the general population (Dinse et al., Arthritis & Rheumatology, 2020). Ordering it without a clinical reason tends to create more questions than answers, which is why I’d rather order an autoimmune workup when the symptoms actually point that direction.