What Blood Tests Should You Have for Hair Loss?

Hair loss can be alarming, particularly when it appears suddenly, continues for several months or has no obvious explanation. It is natural to wonder whether a vitamin deficiency, hormone imbalance, thyroid condition or another health problem could be responsible—and whether a blood test could provide the answer.

Sometimes it can. Iron deficiency, thyroid disease, nutritional deficiencies and certain hormone-related conditions can contribute to excessive shedding or thinning. Blood tests may identify these problems and help guide treatment.

However, blood testing is only one part of a hair-loss assessment. Many common types of hair loss are diagnosed mainly from the pattern of loss, the appearance of the scalp and the history of when the problem began. Male and female pattern hair loss, alopecia areata, scalp inflammation and scarring alopecia cannot be confirmed or ruled out by a general wellness panel.

The right tests therefore depend on what your hair loss looks like, whether you are shedding or gradually thinning, what other symptoms you have and whether there has been a recent trigger such as illness, childbirth, weight loss, surgery or severe stress.

This guide explains which blood tests may be useful for hair loss, what each marker can reveal, when hormone testing is appropriate and when you should arrange a scalp examination rather than ordering progressively larger panels.

First identify what kind of hair loss you have

“Hair loss” can describe several very different processes. Choosing tests before considering the pattern often leads to unnecessary expense and confusing results.

The first useful distinction is between excessive shedding, gradual thinning, clearly defined bald patches and hair loss accompanied by visible scalp disease.

Diffuse shedding

Diffuse shedding means that more hair than usual is being lost from across the scalp. You may notice hair:

• Collecting in the shower or bath
• Coming away during brushing
• Falling onto clothing or bedding
• Gathering around the home
• Coming out when you gently run your fingers through it

The scalp may look generally less dense, but there are no completely bald patches. This pattern commonly occurs with telogen effluvium.

Telogen effluvium happens when an unusually large number of hairs move into the resting and shedding phase of the hair cycle. The trigger may have occurred two or three months before shedding became noticeable.

Possible triggers include:

• A significant infection or high fever
• Surgery or hospital admission
• Childbirth
• Rapid weight loss
• Severe psychological stress
• A major change in diet
• Starting or stopping certain medicines
• Iron deficiency
• Thyroid disease

The British Association of Dermatologists’ guidance on telogen effluvium explains that shedding usually lasts for three to six months, although regaining normal volume can take considerably longer. Blood tests may be used to look for causes such as iron deficiency or thyroid disease.

Gradual patterned thinning

Pattern hair loss develops more gradually.

In men, it commonly affects the temples, frontal hairline and crown. In women, it often causes widening of the central parting and reduced density over the top of the scalp while the frontal hairline remains relatively preserved.

Blood tests are often normal because pattern hair loss is primarily influenced by genetics and the sensitivity of hair follicles to androgens. Testing may still be worthwhile when the loss is unusually rapid, diffuse or accompanied by symptoms suggesting another condition.

Patchy hair loss

Smooth, round or oval bald patches may indicate alopecia areata, an autoimmune form of hair loss. Eyebrows, eyelashes, beard hair and body hair can also be affected.

Alopecia areata is generally diagnosed by examining the hair and scalp. Most people do not require an extensive blood panel to confirm it.

Hair breakage

Not all apparent hair loss comes from the root. Bleaching, heat styling, tight hairstyles, chemical treatments and some hair-care practices can cause the shaft to snap.

Broken hairs of different lengths suggest damage rather than increased shedding. Blood testing cannot identify mechanical or chemical breakage.

Inflamed or scarring hair loss

Burning, pain, itching, redness, scaling, pustules or shiny areas where follicle openings are no longer visible may suggest an inflammatory or scarring condition.

This requires medical assessment. Blood tests alone cannot exclude scarring alopecia, and delaying examination while trying supplements or home tests could allow permanent loss to progress.

When should you see a GP or dermatologist?

Some mild, temporary shedding can be monitored initially, particularly when there has been a clear trigger and regrowth is already visible. However, professional assessment is appropriate when the cause is uncertain or the loss is continuing.

Arrange a GP appointment if:

• Hair loss is sudden or severe
• Shedding continues for more than several months
• You are developing clearly defined bald patches
• Your scalp is painful, inflamed, itchy or heavily scaled
• There is loss of eyebrows, eyelashes or body hair
• The frontal hairline is receding in a band
• The scalp looks smooth or shiny in affected areas
• You have fatigue, weight change, menstrual changes or other symptoms
• You are losing hair after starting a new medicine
• Hair loss is causing significant distress

Seek earlier assessment when there are possible signs of scarring hair loss, such as inflammation, tenderness, burning or disappearance of follicle openings.

A clinician may:

• Examine the distribution of hair loss
• Look for short regrowing hairs or broken shafts
• Perform a gentle hair-pull test
• Examine the scalp with magnification
• Review medicines, diet and recent illnesses
• Ask about periods, pregnancy and menopause
• Arrange selected blood tests
• Refer you to dermatology
• Occasionally arrange a scalp biopsy

Blood tests are most useful when they support this broader assessment rather than being interpreted in isolation.

Which blood tests are commonly considered for hair loss?

There is no universal hair-loss panel that everyone needs. For diffuse shedding or unexplained thinning, a reasonable initial investigation may include:

• Full blood count
• Ferritin
• Thyroid function
• Vitamin B12 and folate where relevant
• Vitamin D in selected circumstances

Depending on the symptoms and history, additional testing may include:

• Transferrin saturation and other iron studies
• Coeliac disease antibodies
• Testosterone and SHBG
• DHEAS
• Prolactin
• FSH, LH or oestradiol
• HbA1c
• Liver and kidney function
• Zinc or other micronutrients in carefully selected cases

The ideal starting set is often relatively small. A full blood count, ferritin and thyroid function can address several common medical contributors to diffuse hair loss. Further markers should be added when your diet, symptoms or examination provide a reason.

Before purchasing a panel, read our guide to choosing the right private blood test. It explains why a targeted test can be more useful than the package containing the largest number of biomarkers.

Full blood count, ferritin and iron studies

Full blood count

A full blood count, or FBC, measures red blood cells, white blood cells and platelets. It is commonly requested when hair loss may be related to anaemia or another underlying condition.

Relevant results include:

• Haemoglobin
• Red blood cell count
• Haematocrit
• Mean cell volume, or MCV
• Mean cell haemoglobin, or MCH
• White blood cell count
• Platelet count

Iron-deficiency anaemia commonly causes low haemoglobin and may also produce small, pale red blood cells. Other forms of anaemia may be linked to vitamin B12 or folate deficiency, chronic disease, bleeding or less common blood disorders.

A normal full blood count is reassuring, but it does not rule out depleted iron stores. Ferritin can become low before haemoglobin falls below the reference range.

Our guide to full blood count results explains the main measurements and what abnormal patterns may mean.

Ferritin

Ferritin is a protein used to store iron. It is one of the most frequently considered blood tests in people with diffuse shedding, particularly when there are risk factors for iron deficiency.

These include:

• Heavy periods
• Pregnancy or recent childbirth
• Regular blood donation
• A vegan, vegetarian or restrictive diet
• Low calorie intake
• Rapid weight loss
• Digestive symptoms or malabsorption
• Previous bariatric or gastrointestinal surgery
• Known bleeding

Low ferritin may occur even when haemoglobin remains normal. This is often called iron deficiency without anaemia.

Possible accompanying symptoms include:

• Fatigue
• Reduced exercise tolerance
• Breathlessness
• Headaches
• Restless legs
• Feeling cold
• Difficulty concentrating

Read our guide to low ferritin with normal haemoglobin for a detailed explanation.

There is no single “hair growth ferritin level”

Online discussions sometimes claim that ferritin must be above one particular number for hair to grow. The reality is less precise.

Laboratory ranges differ, ferritin is affected by inflammation, and the relationship between mildly reduced iron stores and hair loss is not identical in every person. A result should be considered alongside haemoglobin, red-cell measurements, symptoms, inflammation and the likelihood of blood loss.

Ferritin can also rise during infection, inflammation, liver disease and metabolic illness. A normal or high result does not always mean iron stores are adequate.

When the picture is unclear, a clinician may consider:

• Serum iron
• Transferrin
• Total iron-binding capacity
• Transferrin saturation
• CRP or another inflammation marker

Our guide to iron, ferritin and anaemia results explains how these markers fit together.

Do not take iron without establishing a reason

Iron supplements can cause constipation, nausea and abdominal discomfort. Excess iron can also be harmful.

More importantly, confirmed iron deficiency may require investigation. Heavy periods are a common cause, but gastrointestinal bleeding, coeliac disease, dietary deficiency and poor absorption may also need consideration.

Treating the number without investigating its cause may allow an underlying problem to continue.

Thyroid, vitamin B12, folate and vitamin D

Thyroid function

Both an underactive and an overactive thyroid can affect the hair cycle.

An underactive thyroid may cause:

• Diffuse thinning
• Dry or coarse hair
• Fatigue
• Feeling unusually cold
• Constipation
• Weight gain
• Dry skin
• Heavy or irregular periods
• Slowed thinking or low mood

An overactive thyroid may cause hair thinning alongside:

• Weight loss
• Palpitations
• Tremor
• Sweating
• Heat intolerance
• Anxiety
• Frequent bowel movements

A basic thyroid assessment usually includes thyroid-stimulating hormone, or TSH, and free T4. Free T3 and thyroid antibodies may be appropriate in particular circumstances but are not necessary for every initial investigation.

Our thyroid blood test results guide explains common combinations of TSH, free T4 and free T3.

Vitamin B12 and folate

Vitamin B12 and folate are needed for normal blood-cell formation and many other processes. Severe deficiency may contribute indirectly to hair changes, particularly when it causes anaemia or reflects broader nutritional problems.

Testing may be more relevant when hair loss occurs alongside:

• Fatigue or weakness
• A sore tongue
• Mouth ulcers
• Pins and needles
• Balance or memory problems
• A vegan or highly restrictive diet
• Metformin use
• Long-term acid-suppressing medication
• Coeliac disease or another absorption disorder
• Previous stomach or bowel surgery

Supplements can alter the result, so ideally diagnostic samples should be collected before starting high-dose replacement.

Read our guide to vitamin B12 and folate results for more detail.

Vitamin D

Low vitamin D levels are common in the UK, particularly during autumn and winter. Vitamin D is important for bone, muscle and immune health, and some studies have found associations between low levels and particular forms of hair loss.

That does not mean vitamin D deficiency is the cause of every episode of shedding. Testing is more useful when there are risk factors, bone or muscle symptoms, a malabsorption condition or another clinical reason to know the actual level.

Our vitamin D blood test guide explains UK result categories, supplementation and repeat testing.

Taking very high doses without medical advice is not a safe shortcut. Excess vitamin D can raise calcium and cause harm.

When hormone tests may be useful

Hormone testing is often heavily promoted for hair loss, but it is not required for everyone.

Many people with female or male pattern hair loss have hormone concentrations within standard laboratory ranges. The follicles may be genetically sensitive to normal androgen levels.

Hormone testing becomes more relevant when hair thinning occurs with signs of androgen excess or another reproductive or endocrine problem.

Symptoms suggesting androgen excess

Women may benefit from further hormone assessment when scalp thinning is accompanied by:

• Irregular or absent periods
• New or increasing facial or body hair
• Persistent or severe acne
• Difficulty conceiving
• Rapid progression of hair loss
• Deepening of the voice
• Increased muscle development without explanation

Possible tests include:

• Total testosterone
• SHBG
• Calculated free testosterone or free androgen index
• DHEAS
• Prolactin
• LH and FSH
• HbA1c where PCOS-related metabolic risk is relevant
• Thyroid function

Rapidly developing virilising symptoms require prompt medical assessment rather than routine home testing.

PCOS and hair loss

Polycystic ovary syndrome can be associated with scalp thinning, acne, excess facial or body hair and irregular ovulation.

Blood tests may support the assessment, but PCOS cannot be diagnosed from a single testosterone result. The diagnosis depends on a combination of menstrual history, signs or blood-test evidence of androgen excess, and sometimes ultrasound findings, while excluding other causes.

Our guide to female hormone blood test results explains testosterone, SHBG, LH, FSH, oestradiol, progesterone and prolactin in more detail.

Menopause and perimenopause

Changes in hair density can occur around perimenopause and menopause. Hormonal changes may reveal or accelerate female pattern hair loss, but an FSH test is not always useful.

In otherwise healthy people over 45 with typical symptoms, menopause is usually identified from symptoms and menstrual history rather than a hormone panel. FSH can fluctuate considerably during perimenopause.

Testing may be appropriate when symptoms begin at a younger age, the diagnosis is uncertain or there are other reasons to investigate.

Read our guide to menopause blood tests before purchasing a broad reproductive-hormone panel.

Hormone tests in men

Men with a typical receding hairline or crown thinning do not usually need testosterone testing simply because they are losing hair.

Male pattern hair loss is related mainly to genetic sensitivity to dihydrotestosterone within the follicle. A high blood testosterone result is not required for it to occur.

Male hormone testing may be appropriate when there are separate symptoms such as reduced libido, erectile dysfunction, loss of morning erections, infertility or reduced muscle mass. Fatigue or hair loss alone does not establish testosterone deficiency.

Coeliac disease, restrictive diets and other nutritional tests

Coeliac disease screening

Coeliac disease can interfere with nutrient absorption and contribute to low iron, folate or vitamin B12. Some people have obvious digestive symptoms, while others mainly experience fatigue, anaemia, mouth ulcers or unexplained deficiencies.

Testing may be worth considering when hair loss occurs with:

• Persistent bloating or diarrhoea
• Unexplained iron deficiency
• Weight loss
• Recurrent mouth ulcers
• A family history of coeliac disease
• Type 1 diabetes
• Autoimmune thyroid disease

The initial blood assessment usually includes tTG-IgA and total IgA. You normally need to continue eating gluten before testing; removing it prematurely can produce a falsely reassuring result.

Our guide to coeliac blood test results explains the markers and likely next steps.

Rapid weight loss and insufficient nutrition

Hair production is not essential for immediate survival. When the body is dealing with insufficient energy, inadequate protein or a severe nutritional disturbance, more hairs may enter the resting phase.

Shedding can appear several months after:

• A crash diet
• Major weight loss
• Bariatric surgery
• Severe illness
• An eating disorder
• Persistent vomiting
• Very restricted food intake

Possible investigations depend on the circumstances and may include:

• Full blood count
• Ferritin and iron studies
• Vitamin B12 and folate
• Vitamin D
• Electrolytes
• Liver and kidney function
• Calcium, magnesium and phosphate
• Other micronutrients where clinically justified

Blood tests can appear normal despite inadequate calorie or protein intake. A nutritional and medical assessment may be more informative than a broad micronutrient panel alone.

Zinc

Zinc deficiency can affect hair, skin and wound healing, but routine zinc testing for every person with isolated hair loss is not well supported.

Testing may be more appropriate where there is:

• Severe dietary restriction
• Malabsorption
• Long-term diarrhoea
• Bariatric surgery
• Poor wound healing
• Other clinical signs of deficiency

Zinc supplements should not be taken indefinitely without a reason. Excess zinc can interfere with copper absorption and cause additional health problems.

Biotin

Biotin supplements are widely marketed for hair growth, but true biotin deficiency is rare.

High-dose biotin can interfere with some laboratory tests, potentially producing falsely high or low results. Thyroid, hormone and certain cardiac tests may be affected depending on the laboratory method.

Tell the provider or clinician about biotin-containing supplements before testing and follow their advice about whether they should be paused. Do not stop prescribed treatment without medical guidance.

Why some popular hair-loss blood tests are misleading

The hair-loss market contains many tests that sound comprehensive but may not answer a clinically useful question.

Very large micronutrient panels

Panels containing dozens of vitamins, minerals and trace elements can produce borderline results that are difficult to interpret. Some blood concentrations do not accurately reflect tissue stores, and not every minor variation contributes to hair loss.

A focused assessment based on diet, symptoms and risk factors is usually more useful.

Random hormone panels

Hormone measurements are influenced by:

• Time of day
• Menstrual-cycle timing
• Age
• Pregnancy
• Contraception
• Menopause
• Acute illness
• Medicines

A broad panel taken at an arbitrary time may create more questions than answers. The markers and timing should reflect the condition being investigated.

Cortisol and “adrenal fatigue” tests

Adrenal insufficiency is a recognised medical condition, but “adrenal fatigue” is not an established explanation for routine hair loss.

Cortisol varies through the day and responds to sleep, stress, illness and medication. A random home result should not be used to diagnose an adrenal disorder.

Food intolerance IgG panels

Food-specific IgG tests are sometimes marketed as a way to identify foods causing inflammation and hair loss. IgG commonly reflects exposure to a food rather than proving intolerance.

Removing multiple foods on the basis of such results can worsen nutritional intake and potentially contribute to further shedding.

Using ferritin alone as a diagnosis

A low ferritin result may be important, but it does not prove that iron deficiency is the only cause of hair loss. A normal ferritin does not rule out every iron problem, particularly when inflammation is present.

The whole pattern—including haemoglobin, red-cell measurements, symptoms, menstrual or bleeding history and other iron studies—matters.

Preparing for a hair-loss blood test and interpreting the results

Many common hair-loss blood tests do not require fasting. Full blood count, ferritin, thyroid function, vitamin B12 and vitamin D can often be measured without it.

However, preparation depends on the complete panel. Follow the provider’s instructions.

Tell the provider about medicines and supplements

Relevant products may include:

• Iron
• Vitamin B12
• Folate
• Vitamin D
• Biotin
• Hormonal contraception
• Hormone replacement therapy
• Testosterone
• Thyroid medication
• Hair-loss medicines

Supplements can affect the result and may conceal a deficiency if testing begins after supplementation.

Time hormone tests appropriately

Testosterone is generally measured in the morning. Female reproductive hormones may need to be interpreted according to menstrual-cycle timing.

Do not assume that all hormones can be meaningfully tested on any day at any time.

Do not interpret every borderline result as the cause

Reference ranges describe values found in most members of a reference population. A result just outside the range may be temporary, expected or unrelated to the hair loss.

Ask:

• How far is the result outside the range?
• Do related markers support the same explanation?
• Has the result changed compared with previous tests?
• Could illness, inflammation, supplements or medicines have affected it?
• Does the finding match your symptoms?

Hair recovery takes time

Correcting an underlying deficiency does not stop shedding overnight. Hair follicles work in cycles, so the visible response usually lags behind the improvement in blood results.

Even after the trigger has resolved, shedding may take several months to settle. Restoring previous density can take longer.

Repeated testing every few weeks is rarely useful. The appropriate interval depends on the abnormality, treatment and advice from your clinician.

What if all your blood tests are normal?

Normal results do not mean the hair loss is imaginary, and they do not end the assessment.

Many important causes of hair loss routinely occur with normal blood tests.

Pattern hair loss

Male and female pattern hair loss are mainly diagnosed from their appearance and progression. Blood hormone levels may be normal.

Treatment is more likely to depend on scalp findings, family history, age and suitability for options such as topical minoxidil than on a general blood panel.

Telogen effluvium after a resolved trigger

Blood tests may be normal because the trigger was an infection, childbirth, surgery or period of severe stress that has already passed.

The shedding reflects a delayed change in the hair cycle rather than a currently abnormal blood marker.

Alopecia areata

Alopecia areata is usually identified through examination. Extensive autoimmune blood screening is not required for every person with a bald patch.

Testing may be considered when symptoms or history suggest an associated autoimmune condition, particularly thyroid disease, but normal blood tests do not exclude alopecia areata.

Hair breakage or traction

Heat, bleach, extensions, tight braids, tight ponytails and repeated pulling can damage the shaft or follicles. Blood tests will not show this.

Long-standing traction can eventually cause permanent loss, so changing the hairstyle or practice early matters.

Scalp disease and scarring alopecia

Inflammatory or scarring disorders may require dermoscopy, fungal testing, examination by a dermatologist or a scalp biopsy.

Normal iron, thyroid and vitamin results should not delay referral when the scalp is inflamed, painful or showing possible scarring.

Frequently asked questions

What is the best blood test for hair loss?

There is no single best test. For unexplained diffuse shedding, a full blood count, ferritin and thyroid function are common starting points. Vitamin B12, folate, vitamin D, coeliac antibodies or hormone tests may be added when symptoms and risk factors make them relevant.

Should everyone with hair loss have ferritin tested?

Not everyone needs it, but ferritin is often considered when there is diffuse shedding or a risk of iron deficiency. This is especially relevant for people with heavy periods, restrictive diets, recent childbirth, blood donation, gastrointestinal symptoms or rapid weight loss.

Can low ferritin cause hair loss when haemoglobin is normal?

Low ferritin can occur before anaemia develops and may be associated with diffuse shedding in some people. However, hair loss can have multiple causes, and low ferritin should be interpreted with symptoms, full blood count and other relevant findings.

What ferritin level is needed for hair growth?

There is no universally accepted ferritin threshold that guarantees healthy hair growth. Online targets should not replace clinical interpretation. Laboratory ranges, inflammation, related iron markers and the person’s overall situation all matter.

Can thyroid problems cause hair loss?

Yes. Both underactive and overactive thyroid conditions can cause diffuse thinning. Thyroid-related hair loss usually occurs with other symptoms, although these may be subtle.

Should I have my hormones tested for hair loss?

Hormone testing is most useful when hair loss occurs with irregular periods, acne, excess facial or body hair, fertility difficulties, rapid progression or other endocrine symptoms. Typical male or female pattern hair loss often occurs despite normal blood hormone levels.

Can PCOS cause scalp hair loss?

Yes. PCOS can be associated with androgen-related scalp thinning, particularly when it occurs with irregular periods, acne or excess facial and body hair. Blood tests may support the assessment but cannot diagnose PCOS by themselves.

Does vitamin D deficiency cause hair loss?

Low vitamin D has been associated with some forms of hair loss, but it is not the cause of every episode of shedding. Testing is more useful when there are risk factors, related symptoms or another clinical reason to establish the level.

Should I test zinc or biotin?

Routine zinc or biotin testing is not necessary for most people with isolated hair loss. Zinc testing may be appropriate with severe restriction or malabsorption. True biotin deficiency is rare, while high-dose biotin supplements can interfere with several laboratory tests.

Can stress cause hair loss even if blood tests are normal?

Yes. Severe physical or psychological stress can trigger telogen effluvium. Shedding often begins several months after the stressful event, by which time routine blood tests may be completely normal.

How long does hair take to recover after treating a deficiency?

Visible improvement is slow because hair grows in cycles. Shedding may take several months to reduce, and restoration of density can take six to twelve months or longer. The timing depends on the cause, severity and duration of the problem.

Can a private blood test diagnose the cause of my hair loss?

It can identify possible contributors such as iron deficiency, anaemia or thyroid dysfunction, but it cannot diagnose every cause. Pattern hair loss, alopecia areata, breakage and scarring conditions require assessment of the hair and scalp.

Where can I order private blood tests relevant to hair loss?

Private providers offer targeted iron, thyroid, vitamin and hormone tests as well as broader health panels. Before ordering, check that the panel contains markers relevant to your pattern of hair loss and symptoms rather than simply choosing the largest package.

A range of home and clinic-based blood tests can be viewed through Medichecks via All Health and Care. Use the code ALLHEALTH10 at checkout for an additional discount.

This is an affiliate link, which means All Health and Care may receive a commission if you make a purchase, at no additional cost to you. Private testing can help identify some contributors to hair loss, but it should not replace scalp examination when the loss is patchy, painful, inflamed, rapidly progressing or potentially scarring.