2. When testing is generally not needed

In a man with a typical Hamilton–Norwood pattern, normal scalp skin on examination, and no systemic symptoms, most guidelines suggest that a diagnosis of male androgenetic alopecia can be made clinically without routine blood tests.

Similarly, in a woman with classic FPHL (female pattern hair loss, i.e. central part widening and preserved frontal hairline), no signs of hyperandrogenism (hirsutism, acne, or menstrual disturbance), and no diffuse shedding, systemic symptoms, or nutritional red flags, investigation can be limited or omitted, particularly if she is older and otherwise well.

In other words, if the presentation aligns with what is commonly seen in genetically driven hair loss, whether male or female, no laboratory tests are needed. However, if other unaccounted-for medical symptoms accompany the alopecia, tests are indicated.

It is not a black-and-white issue, however, and ultimately comes down to the clinician's judgment.

In ambiguous cases, tests may be considered if there is diagnostic uncertainty, treatment has failed in unexpected ways, or the patient prefers to have a baseline haematological and metabolic assessment. However, routine extensive laboratory testing for every person with pattern hair loss is not supported by the evidence.

3. Situations where testing is usually appropriate

3.1 Diffuse shedding and suspected telogen effluvium

In diffuse hair shedding, especially when no clear trigger is present, initial blood work is usually warranted. Typical tests include:

• Full blood count (FBC) – to identify anaemia or haematological abnormalities;
• Serum ferritin – as a marker of iron stores;
• Thyroid-stimulating hormone (TSH) (and sometimes free T4) – to screen for hypo- or hyperthyroidism;
• Vitamin B12 and folate – if diet is restricted or there are neurological or haematological signs;
• Vitamin D – frequently low in the general population; its exact role in hair biology is still under investigation, but severe deficiency should be corrected;
• Zinc – selectively, if diet, GI history or other features suggest deficiency.

These tests aim to uncover systemic contributors to telogen effluvium rather than to directly diagnose a hair disease.

3.2 Women with signs of hyperandrogenism

In women with hair loss and clinical features of androgen excess (e.g. hirsutism, persistent acne, irregular or absent menses), endocrine evaluation is appropriate. This may include:

• Total testosterone and sex hormone-binding globulin (SHBG), from which the free androgen index can be calculated;
• DHEAS (dehydroepiandrosterone sulfate) – an adrenal androgen;
• Androstenedione (in some protocols);
• Prolactin – when indicated by galactorrhoea or menstrual disturbance;
• LH and FSH – if PCOS or ovulatory issues are suspected.

The aim is to detect or characterise conditions such as polycystic ovary syndrome, non-classic congenital adrenal hyperplasia, or androgen-secreting tumours. Findings guide whether anti-androgen therapy or input from an Endocrinologist is appropriate.

3.3 Suspected autoimmune or connective tissue disease

When hair loss coexists with systemic symptoms such as joint pain, fevers, photosensitivity, other skin signs (malar rash, discoid plaques, livedo), then autoimmune screening may be warranted, including but not limited to:

• ANA (antinuclear antibodies) and, if indicated, extractable nuclear antigen panels;
• ESR/CRP as general inflammatory markers;
• specific autoantibodies depending on clinical suspicion (there are many).

In discoid lupus erythematosus or mixed connective tissue disease, blood tests support the histological and clinical findings. Input from a Rheumatologist is necessary here.

3.4 Scarring alopecia and inflammatory scalp disease

In primary scarring alopecias (lichen planopilaris, frontal fibrosing alopecia, CCCA, discoid lupus, folliculitis decalvans, dissecting cellulitis), blood tests themselves do not diagnose the hair disorder, but may be used to:

• assess systemic involvement (e.g. serology in lupus);
• rule out infection (e.g. culture in suspected tinea capitis or bacterial folliculitis);
• establish baseline organ function before systemic therapy (e.g. liver and kidney function before hydroxychloroquine, methotrexate, retinoids, or long-term antibiotics).

A biopsy is required to confirm the diagnosis in these cases, but laboratory testing can help narrow this down. Dermatology input is needed here.

3.5 Patients with substantial systemic symptoms

In any patient with hair loss and systemic symptoms such as fatigue, weight changes, night sweats, gastrointestinal disturbances, or lymphadenopathy (swollen glands), a broader work-up may be needed, as these symptoms may suggest anything from chronic infection, liver cirrhosis, an autoimmune process, or even cancer.

It's unlikely that alopecia will be the chief complaint in this scenario, given the severity of the other symptoms. These patients will require hospital admission for workup.

3.6 Children

In children, the laboratory work-up is often guided by suspicion of tinea capitis (a fungal infection that requires scalp scrapings or hair plucks for microscopy and culture rather than blood tests), by the presence of systemic signs, and by signs of nutritional deficiency or chronic disease.

Routine extensive blood work for isolated mild alopecia areata in an otherwise well child is not generally recommended in the absence of other autoimmune or systemic clues.

4. Commonly used tests and what they mean

4.1 Full blood count (FBC)

Assesses for anaemia (low red blood cells), thrombocytopaenia (low platelets), or leucopaenia (low white cells), and other haematological (blood-related) abnormalitie.

Anaemia from iron deficiency, chronic disease or B12/folate deficiency can contribute to diffuse shedding.

4.2 Ferritin and iron studies

Ferritin is an iron-storage protein, and thus its levels reflect iron storage, whereby very low ferritin (<15–20 μg/L) strongly suggests iron deficiency.

Some authors recommend aiming for ferritin above 30–50 μg/L in hair loss patients, though evidence for a strict threshold is mixed.

If ferritin is low and there are risk factors (heavy menstruation, gastrointestinal bleeding, vegan diet, malabsorption), iron supplementation and further evaluation may be warranted. Iron studies (serum iron, total iron-binding capacity, transferrin saturation) help confirm the diagnosis.

4.3 Thyroid function tests

The thyroid gland, which sits anteriorly in our neck, produces thyroid hormone that drives the metabolic rate of our cells and, by extension, our organs.

TSH (thyroid-stimulating hormone) and sometimes free T4 are used to detect:

• hypothyroidism (high TSH, low/normal free T4);
• hyperthyroidism (low TSH, high free T4).

Both hypo- and hyperthyroidism can cause diffuse shedding and hair texture changes. Treating the thyroid disorder typically improves hair over several cycles.

4.4 Vitamin B12, folate and vitamin D

• B12 and folate deficiency can cause anaemia and neurological symptoms; hair changes are usually part of a broader picture.
• Vitamin D deficiency is common; severe deficiency should be corrected to support bone and overall health. Some studies suggest an association between low vitamin D levels and various alopecias, but causality remains uncertain.

Routine high-dose supplementation in the absence of deficiency has not been shown to improve hair growth.

4.5 Zinc and other trace elements

Zinc testing may be considered in patients with a poor diet, gastrointestinal disease, or unexplained diffuse hair shedding.

Severe zinc deficiency is known to cause hair loss, but moderate “low-normal” levels are more difficult to interpret. Excess zinc can impair copper absorption and worsen hair if taken indiscriminately.

Trace elements, such as copper and selenium, are measured selectively, particularly in the context of gastrointestinal surgery, malabsorption, or suspected toxicity.

4.6 Androgen panel in women

As noted, in women with suspected hyperandrogenism, an androgen panel can:

• delineate the source and degree of androgen excess;
• differentiate PCOS-like patterns from more serious causes (such as tumours);
• guide decisions on hormonal therapies.

Interpretation requires an understanding of assay limitations and should generally be integrated with clinical and ultrasound findings in endocrinology or gynaecology.

5. Tests that are often unnecessary and why

In the absence of specific indications, this kind of broad, untargeted testing:

• rarely changes management;
• increases cost and anxiety;
• risks incidental findings that lead to further invasive testing without clear benefit.

Guidelines and reviews generally advise against:

• blanket testing for autoantibodies in all hair loss patients;
• ordering exhaustive “vitamin panels” without nutritional history;
• using lab tests to “rule out all causes” when clinical patterning clearly indicates AGA and the patient is otherwise well.

The principle is that tests should be used when the pre-test probability of a condition is meaningful and when the result would genuinely alter treatment.

6. Pitfalls and special considerations

6.1 Biotin interference

High-dose biotin (vitamin B7), often taken for hair and nail health, can interfere with many immunoassays, including those for:

• thyroid function (TSH, free T4, free T3),
• troponin (heart muscle breakdown marker),
• hormone levels,
• and some tumour markers.

This can produce falsely normal or abnormal results, potentially leading to misdiagnosis. Many laboratories now advise stopping high-dose biotin 48–72 hours before testing; in practice, if a patient takes hair supplements containing biotin, it is important that the lab and clinician are aware of this.

6.2 Borderline abnormalities

Marginal deviations (for example, slightly low vitamin D, minimally low ferritin, mildly raised ANA) need to be interpreted cautiously:

• vitamin D insufficiency is so common that treatment decisions are better based on overall health than hair alone;
• very low ferritin suggests iron deficiency; borderline ferritin may warrant observation or gentle supplementation rather than aggressive treatment;
• a low-titre positive ANA (antinuclear antibody) without clinical features of autoimmune disease is common in the general population and does not necessarily imply lupus or similar conditions.

Avoiding the temptation to equate every borderline result with a causality of hair loss is part of maintaining perspective.

6.3 Overlapping causes

It is common for more than one factor to be present:

• a woman with FPHL and heavy periods may have both pattern loss and iron deficiency;
• a man with early AGA who has recently had a prolonged febrile illness may have concurrent telogen effluvium.

Laboratory results need to be interpreted alongside trichoscopy and history. Correcting a deficiency may improve shedding, but underlying pattern hair loss may still need direct treatment.

7. A pragmatic, tiered approach

A tiered approach, broadly consistent with guidelines and reviews, might look like this:

Tier 1 – No or minimal testing

• Classic male AGA in a healthy man with no systemic symptoms.
• Established FPHL in an older woman with no signs of androgen excess or systemic disease and stable hair loss.

Here, the focus is on clinical diagnosis and treatment options; tests are reserved for atypical features.

Tier 2 – Basic screening

• Diffuse shedding where TE is suspected.
• Early or mixed-pattern hair loss in women.
• AGA or FPHL in someone with risk factors for deficiency (dietary restriction, heavy menstruation, gastrointestinal disease).

Basic tests:

• FBC, ferritin;
• TSH (+/− free T4);
• vitamin D;
• B12/folate when indicated;
• zinc selectively.

Tier 3 – Extended work-up

• Hair loss with clear signs of androgen excess in women.
• Hair loss with systemic features suggesting autoimmune or connective tissue disease.
• Children with hair loss plus systemic signs, or refractory cases.

These tiers incorporate endocrine panels, autoimmune screens, and disease-specific tests, guided by history and clinical examination.

8. What this means for patients

From a patient’s perspective, it is reasonable to expect that:

• your doctor will explain why particular tests are or are not being ordered;
• you won’t be sent for large panels “just to see” without discussion;
• mildly abnormal results will be interpreted thoughtfully, not automatically labelled as the definitive cause of your hair loss;
• any significant abnormalities will prompt clear plans for correction or referral.

If you feel that your concerns about hair loss are being dismissed without examination, or conversely that you are being over-tested without clear reasoning, it is appropriate to ask for clarification or to seek a second opinion.