What hormone tests are relevant for hair loss in women?

For women with hair loss — especially pattern thinning at the crown or temples — the relevant hormone tests are: free testosterone (elevated levels can drive androgenic alopecia), DHEAS (an adrenal androgen elevated in conditions like congenital adrenal hyperplasia and PCOS), sex hormone binding globulin (SHBG — low SHBG increases the fraction of free, active testosterone), and LH and FSH (to help assess for PCOS). Prolactin is worth checking if periods are irregular or there is galactorrhoea. These are rarely included in a standard panel and must be requested specifically.

Can I order hair loss blood tests without a doctor?

In most countries a doctor's referral is required, but direct-to-consumer lab services exist. In the US: Ulta Lab Tests and Walk-In Lab offer full iron panels, thyroid panels, and hormone panels without a referral. In the UK: Medichecks offers a dedicated hair loss blood test panel. Prices vary — a comprehensive hair loss panel typically runs £80–150 in the UK and $100–200 in the US.

Blood Tests for Hair Loss: What to Ask For

Q: What blood tests should I ask for if I have hair loss?

A thorough hair loss workup covers four cause clusters: iron status (CBC + ferritin — the most commonly missed test), thyroid function (TSH + free T3 + free T4 + TPO antibodies — not TSH alone), hormones and androgens (free testosterone, DHEAS, SHBG; LH and FSH for women), and nutritional deficiencies (vitamin D, zinc, B12, folate). Standard panels rarely include ferritin, free thyroid hormones, or androgen markers — these need to be requested specifically.

Q: What is the most important blood test for hair loss?

Ferritin is consistently the most clinically significant and most commonly missed test for hair loss. A standard CBC measures haemoglobin but not ferritin — the protein that stores iron in tissues. Ferritin can be significantly depleted while haemoglobin remains normal, and research (Rushton et al., Journal of Cosmetic Dermatology, 2002) has linked low ferritin to telogen effluvium (diffuse shedding) in women. Most dermatologists and trichologists target ferritin above 40–70 ng/mL for hair health, well above many labs' flagging threshold of 12 ng/mL.

Q: Does low ferritin cause hair loss?

Research supports a link between low ferritin and telogen effluvium (diffuse hair shedding), particularly in women. A 2002 study by Rushton et al. found that ferritin below 40 μg/L was significantly more common in women with unexplained diffuse hair loss compared to controls. Many dermatologists use a functional threshold of 40–70 ng/mL for hair health — higher than the standard lab flagging threshold of 12–15 ng/mL. A CBC that shows normal haemoglobin does not rule out low ferritin.

Q: Can thyroid problems cause hair loss?

Yes. Both hypothyroidism (underactive thyroid) and hyperthyroidism (overactive) can cause diffuse hair shedding. Autoimmune thyroid disease (Hashimoto's) is particularly associated with hair loss and can be present even when TSH is within normal range — which is why TPO antibodies are an important addition to a standard TSH-only test. Hair loss is often one of the earlier symptoms of thyroid dysfunction.

Q: How long does it take for hair to regrow after fixing a deficiency?

Hair growth is slow. After correcting a deficiency, most people notice reduced shedding within 2–4 months, but visible regrowth typically takes 6–12 months — this reflects the hair growth cycle, not treatment failure. Iron stores (ferritin) take 3–6 months to rebuild. Thyroid treatment takes 6–8 weeks to stabilise hormones, with hair response lagging a further 3–6 months. Vitamin D and zinc supplementation may reduce shedding in 8–12 weeks if deficiency was the primary cause.

Why a standard panel won't find the cause of hair loss

A routine CBC and metabolic panel screens for disease. it is not designed to investigate hair loss as a symptom.

When you go to your doctor concerned about hair shedding, you'll typically receive a standard blood count and perhaps a single TSH test. This is a reasonable starting point, but it leaves several major causes uninvestigated.

A CBC measures haemoglobin, which only drops after iron stores are already severely depleted. It does not include ferritin — the iron storage protein that many dermatologists regard as the single most important blood test in a hair loss workup. A standard TSH measures the pituitary's signal to the thyroid, but does not include free T3, free T4, or TPO antibodies — all of which are relevant when thyroid-driven hair loss is suspected. And hormonal causes, elevated androgens, low SHBG, and PCOS require specific tests that are almost never part of a routine annual panel.

The four cause clusters below are what a thorough hair loss investigation actually covers. Not every cluster applies to every person, the hormonal cluster, in particular, differs significantly between men and women, but knowing which tests exist and what to ask for puts you in a much better position.

The 4 test clusters for hair loss

Organised by cause. Each cluster lists tests your panel should include, and additional tests worth requesting specifically.

Cluster 1 of 4

Iron & Ferritin

Iron depletion, specifically low ferritin, is one of the most common and most overlooked causes of diffuse hair shedding, particularly in women. A normal CBC does not rule it out.

Core Usually included in standard CBC Ask Request specifically

Core

Complete Blood Count (CBC)

Measures haemoglobin, MCV, RBC. Catches frank anaemia, but haemoglobin only drops after iron stores are severely depleted. A normal CBC does not rule out iron depletion as a cause of hair loss.

Ask

Ferritin

The single most important test in a hair loss workup. Measures iron stores, not circulating iron. Many labs flag only <12–15 ng/mL; most dermatologists and trichologists use a functional target of >40–70 ng/mL for hair health. Must be requested separately. it is not included in a standard CBC.

Ask

Serum Iron + TIBC + Transferrin Saturation

The full iron panel. Transferrin saturation <20% alongside low ferritin confirms iron deficiency and helps distinguish it from anaemia of chronic disease, where ferritin can appear falsely elevated.

Cluster 2 of 4

Thyroid Function

Both underactive and overactive thyroid cause diffuse hair shedding. Autoimmune thyroid disease (Hashimoto's) can cause hair loss even when TSH is technically normal.

Core Usually included in standard panel Ask Request specifically

Core

TSH (Thyroid-Stimulating Hormone)

The standard first-line thyroid screen. ATA normal range: 0.4–4.0 mIU/L. TSH at the higher end of normal (2.5–4.0) alongside hair thinning and fatigue is worth investigating further even without a flag. Full TSH guide →

Ask

Free T4 (FT4) + Free T3 (FT3)

FT4 is the thyroid's primary output; FT3 is the active hormone cells use. Low-normal FT4 with high-normal TSH can indicate sluggish output not yet captured by TSH. Some people convert T4 to T3 poorly, producing ongoing symptoms despite normal TSH and T4.

Ask

TPO Antibodies (Anti-TPO)

Tests for Hashimoto's thyroiditis, the most common cause of autoimmune thyroid disease. Elevated antibodies can drive hair loss and fluctuating thyroid function even when TSH appears normal. Hair loss is frequently the presenting symptom before TSH moves.

Cluster 3 of 4

Hormones & Androgens

Pattern hair loss at the crown or temples is often androgen-driven. In women, elevated androgens or low SHBG can cause significant hair thinning that is completely invisible on a standard panel.

Core Sometimes included Ask Usually requires specific order

Ask

Free Testosterone

The biologically active fraction of testosterone. Elevated free testosterone in women is the primary hormonal driver of androgenic alopecia. Standard panels measure total testosterone, free testosterone must be specifically requested and is the more relevant value.

Ask

SHBG (Sex Hormone Binding Globulin)

The protein that binds testosterone, reducing its activity. Low SHBG means more free testosterone is available to act on hair follicles. Low SHBG with normal total testosterone can still drive androgenic hair loss, making this an important pairing.

Ask

DHEAS (Dehydroepiandrosterone Sulfate)

An adrenal androgen elevated in conditions such as PCOS and congenital adrenal hyperplasia. Elevated DHEAS is a common finding in women with diffuse hair thinning and irregular periods. Almost never included in a standard panel.

Ask

LH + FSH (Women)

Luteinising hormone and follicle-stimulating hormone. An elevated LH:FSH ratio (>2:1) is a marker for PCOS, one of the most common hormonal causes of hair thinning in women of reproductive age. Relevant if periods are irregular.

Ask

Prolactin

Elevated prolactin (hyperprolactinaemia) suppresses sex hormones and can cause hair loss alongside menstrual irregularities or unexpected lactation. Worth checking if these symptoms are present alongside hair shedding.

Cluster 4 of 4

Nutritional Deficiencies

Zinc, vitamin D, and B12 deficiencies are all associated with hair shedding and are rarely part of a standard annual panel. Biotin is popular but almost never actually deficient outside specific medical conditions.

Core Sometimes included Ask Usually requires specific order

Ask

Zinc

Zinc deficiency causes diffuse hair loss and is among the more commonly underordered nutritional tests. Serum zinc <70 μg/dL is associated with hair loss in multiple studies. Vegetarians and those with GI conditions are at higher risk. Note: taking biotin supplements can falsely skew thyroid test results, stop at least 3–5 days before blood draw if taking high-dose biotin.

Ask

Vitamin D (25-OH)

Vitamin D receptors are expressed in hair follicles. Deficiency (<20 ng/mL) and insufficiency (20–29 ng/mL) are both associated with hair cycling disruption. Most labs only flag <20 ng/mL, leaving the insufficiency zone unmarked.

Ask

Vitamin B12 + Folate

B12 deficiency is associated with hair loss, particularly in vegans, those over 60, and people taking metformin or proton pump inhibitors. Folate supports cell division in hair follicles. Both are usually omitted from standard panels.

The ferritin question, answered

Why your ferritin might be "normal" and still be the problem

This is the most common reason a hair loss workup comes back "all clear" when it shouldn't. A standard lab flags ferritin as low only below 12–15 ng/mL. Most clinical labs define "normal" as anything above that threshold, which means a ferritin of 16 ng/mL gets a green tick on your report.

Research by Rushton et al. (Journal of Cosmetic Dermatology, 2002) found that ferritin below 40 μg/L was significantly more common in women with unexplained diffuse hair loss compared to controls with no hair loss. Most dermatologists who specialise in hair loss use a functional target of 40–70 ng/mL, levels well above the standard lab flagging threshold but where iron stores are genuinely adequate for hair follicle function.

If your ferritin came back "normal" at 18–30 ng/mL, discuss with your doctor whether iron repletion is appropriate given your symptoms. This is not the same as having anaemia, haemoglobin can be completely normal while ferritin remains in a range that may not support optimal hair growth.

Your questions, answered

What blood tests should I ask for if I have hair loss?

A thorough hair loss workup covers four clusters: iron status (CBC + ferritin + transferrin saturation), thyroid function (TSH + free T3 + free T4 + TPO antibodies. not TSH alone), hormones and androgens (free testosterone, SHBG, DHEAS; LH and FSH for women if PCOS is suspected), and nutritional deficiencies (zinc, vitamin D, B12, folate). Standard panels rarely include ferritin, free thyroid hormones, or androgen markers. these need to be requested specifically.

What is the most important blood test for hair loss?

Ferritin. It is consistently the most clinically significant and most commonly omitted test. A standard CBC measures haemoglobin, ferritin, the protein that stores iron in tissues, is a separate order. It can be significantly depleted while haemoglobin remains completely normal. Research (Rushton et al., 2002) linked ferritin below 40 μg/L to telogen effluvium in women. Most dermatologists use a functional target of 40–70 ng/mL for hair health, well above the standard lab flagging threshold of 12–15 ng/mL.

Does low ferritin cause hair loss?

Research supports an association between low ferritin and telogen effluvium, diffuse hair shedding, particularly in women. The mechanism is thought to involve iron's role in DNA synthesis in the rapidly dividing cells of hair follicles. The evidence is strongest at ferritin below 30–40 ng/mL, though some clinicians target higher levels (>70 ng/mL) for patients with ongoing shedding. A CBC that shows normal haemoglobin does not rule out low ferritin.

Can thyroid problems cause hair loss?

Yes. Both hypothyroidism (underactive) and hyperthyroidism (overactive) cause diffuse hair shedding, typically presenting as thinning across the whole scalp rather than a specific pattern. Autoimmune thyroid disease (Hashimoto's) is particularly common and can produce significant hair loss even when TSH is within the normal range, which is why TPO antibodies are an important addition to the standard TSH test. Hair loss often precedes other obvious symptoms of thyroid dysfunction.

What hormone tests are relevant for female hair loss?

For women with hair thinning, particularly at the crown or in a diffuse pattern, the key hormone tests are: free testosterone (elevated levels drive androgenic alopecia), SHBG (low SHBG means more free testosterone is biologically active), DHEAS (an adrenal androgen elevated in PCOS and related conditions), and LH + FSH (an elevated LH:FSH ratio >2:1 is a marker for PCOS). Prolactin is worth including if periods are irregular. These are rarely included in a standard panel and require specific ordering.

Can I order these tests without a doctor?

In most countries a doctor's referral is required, but direct-to-consumer lab services exist. In the US: Ulta Lab Tests and Walk-In Lab offer dedicated hair loss panels. In the UK: Medichecks offers a specific hair loss blood test. Prices vary, a comprehensive panel typically runs £80–150 in the UK and $100–200 in the US. Note: if you take biotin supplements, stop them 3–5 days before your blood draw, as high-dose biotin interferes with thyroid immunoassays.

How long does it take for hair to regrow after fixing a deficiency?

Hair growth is slow. After correcting an underlying deficiency, most people notice reduced shedding within 2–4 months, but visible regrowth typically takes 6–12 months. this reflects the hair growth cycle, not treatment failure. Iron stores (ferritin) take 3–6 months to rebuild. Thyroid treatment takes 6–8 weeks to stabilise hormones, with hair response lagging a further 3–6 months. Zinc and vitamin D supplementation may reduce shedding in 8–12 weeks if deficiency was the primary driver.

Medical disclaimer: FixFirst is an educational tool, not a medical device. Content is reviewed by a qualified medical advisor. Reference ranges and thresholds cited are based on published clinical guidelines and peer-reviewed research including guidelines from the ATA, NICE, the Endocrine Society, and NIH, as well as studies published in the Journal of Cosmetic Dermatology and the Journal of the American Academy of Dermatology. Always consult a licensed healthcare provider before making changes to your health plan.

Blood Tests for Hair Loss: What to Ask For (and What Standard Panels Miss)

Why a standard panel won't find the cause of hair loss

The 4 test clusters for hair loss

Why your ferritin might be "normal" and still be the problem

How to ask, and what to say if your doctor pushes back

Once you have your results

Your questions, answered

Already have results? See which hair loss markers are hiding in yours.