Hair Loss Blood Tests: What Can They Tell Us?

When you notice increased shedding, a widening part, thinning through the crown or a change in the density of your hair, it is natural to want to understand why it is happening.

Hair loss can develop for many different reasons. Genetics, hormonal changes, illness, stress, medications, nutritional deficiencies and certain medical conditions can all affect the hair growth cycle. In some cases, more than one factor may be contributing at the same time.

Blood tests can help identify—or rule out—some of the underlying health and nutritional factors that may be contributing to hair loss. However, there is no single blood test that can diagnose every type of hair loss.

The most useful approach combines your medical history, symptoms, scalp examination, hair-loss pattern and, where appropriate, blood-test results.

What Is a Hair Loss Blood Test?

A “hair loss blood test” is not one specific test. It usually refers to a selection of blood tests requested by a doctor based on the individual’s symptoms, health history, diet, medications and type of hair loss.

Blood tests may help identify conditions such as:

• Iron deficiency or anaemia

• Thyroid dysfunction

• Vitamin or nutritional deficiencies

• Hormonal changes or androgen excess

• Inflammation or autoimmune activity

• Other underlying health conditions that may be affecting the hair cycle

Blood tests are particularly helpful when hair loss is sudden, excessive or diffuse, or when it occurs alongside symptoms such as fatigue, menstrual changes, weight changes or feeling generally unwell.

However, normal blood results do not necessarily mean that there is no explanation for your hair loss. Female and male pattern hair loss, for example, can occur even when routine blood-test results and hormone levels are within the normal range.

Why Early Assessment Matters

Hair grows slowly, and changes within the hair-growth cycle may begin several months before increased shedding becomes noticeable.

An early assessment provides an opportunity to:

• Identify possible contributing factors

• Address nutritional deficiencies or underlying health concerns

• Establish a photographic and microscopic baseline

• Monitor whether the condition is progressing

• Discuss suitable treatment and home-care options

• Help protect and support follicles that are still active

It is important to remember that hair regrowth takes time. Even when an underlying issue is identified and corrected, it may take several months for shedding to settle and for visible improvements in growth or density to appear.

Who Should Consider Speaking to Their Doctor About Blood Tests?

It may be helpful to discuss blood testing with your GP if you are experiencing:

• Excessive or persistent hair shedding

• Sudden, unexplained hair loss

• Overall thinning or a finer hair texture

• A widening part line

• Thinning through the crown or frontal area

• Patchy hair loss

• A receding hairline

• Hair loss that has not improved with previous treatment

• Hair loss following illness, surgery, pregnancy or rapid weight loss

• Hair loss alongside heavy or irregular periods

• New acne, increased facial hair or other possible hormonal symptoms

• Fatigue, weakness, dizziness or shortness of breath

• Unexplained changes in weight

• Changes in appetite, bowel habits or temperature tolerance

• A restrictive diet or concerns about nutritional intake

Most people naturally shed approximately 50–100 hairs each day. What matters is whether you are noticing a significant change from what is normal for you, especially when the shedding continues or is accompanied by visible thinning.

What Blood Tests May Be Considered for Hair Loss?

The tests requested will depend on your individual circumstances. Not everyone requires every test listed below.

Full Blood Count

A full blood count, sometimes called an FBC or CBC, measures red blood cells, white blood cells, haemoglobin and platelets.

It can help identify anaemia and other abnormalities that may require further investigation. Anaemia may reduce the amount of oxygen delivered to the body’s tissues and can be associated with fatigue, weakness and increased hair shedding.

Ferritin and Iron Studies

Ferritin is a measure of the body’s stored iron. It is possible to have low iron stores even when haemoglobin remains within the laboratory reference range.

Iron deficiency is a recognised contributor to diffuse hair shedding and may be more likely in people who:

• Experience heavy menstrual bleeding

• Follow a vegetarian, vegan or restrictive diet

• Have recently been pregnant

• Have digestive or absorption problems

• Have experienced significant blood loss

• Do not regularly consume iron-rich foods

Ferritin results must be interpreted in context because inflammation and certain health conditions can cause ferritin levels to appear normal or elevated. Your doctor may request additional iron studies or inflammatory markers if needed.

Iron supplements should not be started without appropriate advice. Excess iron can be harmful, and the reason for an iron deficiency should also be investigated.

Thyroid Function

Both an underactive thyroid and an overactive thyroid can disrupt the normal hair-growth cycle and contribute to diffuse thinning or shedding.

Thyroid testing may include thyroid-stimulating hormone, known as TSH, and sometimes free T4 or additional thyroid tests.

Possible signs of a thyroid condition can include:

• Unexplained weight changes

• Fatigue

• Feeling unusually hot or cold

• Changes in heart rate

• Dry skin

• Changes in bowel habits

• Menstrual changes

• Anxiety or low mood

Hair loss alone does not confirm a thyroid disorder, but thyroid function may be worth investigating when other symptoms are present.

Vitamin B12 and Folate

Vitamin B12 and folate support healthy red blood-cell formation and normal cell division.

Testing may be considered when someone has dietary risk factors, anaemia, digestive problems, fatigue or other symptoms suggesting a possible deficiency. People following vegan or restrictive diets may be at greater risk of vitamin B12 deficiency unless they use an appropriate supplement or consume fortified foods.

A deficiency does not cause every case of hair loss, but it may contribute to poor hair quality or shedding in some individuals.

Vitamin D

Vitamin D has several roles within the body and is involved in normal follicle activity and immune regulation.

Low vitamin D levels have been observed in association with some hair-loss conditions. However, a low result does not necessarily prove that vitamin D deficiency is the sole cause of hair loss.

Testing may be considered when there are additional risk factors or symptoms. Supplementation and dosage should be discussed with a doctor or qualified healthcare professional.

Zinc

Zinc is involved in cell growth, tissue repair and normal hair-follicle function.

A zinc test may be considered when someone has a restrictive diet, poor nutritional intake, digestive or absorption concerns, or symptoms suggesting deficiency. Low zinc may occasionally be associated with conditions such as coeliac disease.

Routine zinc supplementation is not suitable for everyone. Taking excessive zinc can lead to side effects and may interfere with the absorption of other important nutrients, including copper.

Hormone and Androgen Testing

Hormone testing is not automatically required for everyone experiencing hair loss.

It may be considered for women who have signs of possible androgen excess or another hormonal condition, such as:

• Irregular or absent periods

• New or persistent acne

• Increased facial or body hair

• Fertility concerns

• Sudden or rapidly progressing patterned hair loss

• Other symptoms associated with polycystic ovary syndrome

Depending on the symptoms, a doctor may consider tests such as total testosterone, sex hormone-binding globulin, a calculated free androgen index, DHEA-S or prolactin.

Female pattern hair loss can still occur when androgen levels are normal. Blood tests are therefore only one part of the assessment.

Autoimmune and Inflammatory Testing

Some autoimmune conditions can affect the hair follicles or cause inflammation that contributes to hair loss.

Testing such as antinuclear antibodies, CRP or ESR may be considered if there are other symptoms suggesting autoimmune disease or systemic inflammation. These tests are not routinely required for every person with hair loss.

Patchy hair loss, scalp inflammation, scarring, pain or rapid progression should be assessed by an appropriate medical professional.

Additional Testing

Tests may occasionally be considered depending on the person’s symptoms and medical history. These might include:

• Liver or kidney function

• Coeliac disease screening

• Blood glucose or metabolic testing

• Infection screening

• Additional endocrine investigations

• Syphilis can sometimes cause patchy hair loss during secondary infection, but syphilis testing is not routinely included in every hair-loss assessment. It may be recommended when a person’s symptoms, examination findings or sexual-health history indicate that testing is appropriate.

Can Blood Tests Diagnose the Type of Hair Loss?

Blood tests may identify factors contributing to hair loss, but they usually cannot diagnose the hair-loss condition on their own.

For example, blood tests cannot independently confirm:

• Female pattern hair loss

• Male pattern hair loss

• Traction alopecia

• Alopecia areata

• Scarring alopecia

• Hair-shaft damage

• Many scalp conditions

Diagnosis may require a detailed history, examination of the scalp, magnified imaging or dermoscopy, a hair-pull test, and occasionally assessment by a dermatologist or scalp biopsy.

What If All My Blood Tests Are Normal?

Normal blood-test results are reassuring, but they do not mean that your concerns are not valid.

Many people with genetic or patterned hair loss have completely normal routine blood results. Hair loss may also relate to:

• Genetic sensitivity within the follicles

• Ageing

• Menopause or hormonal transition

• Physical or emotional stress

• Recent illness or surgery

• Pregnancy and postpartum changes

• Rapid weight loss

• Certain medications

• Tight hairstyles or repeated tension

• Scalp inflammation

A scalp and hair assessment can help identify visible patterns, miniaturisation, changes in density and signs of follicle activity that may not appear in a blood test.

How Hair Again Clinic Can Help

At Hair Again Clinic, we take time to understand what you have noticed, when the changes began and what may have been happening around that time.

Your consultation may include:

• A detailed discussion about your hair-loss history

• Review of relevant health, dietary and lifestyle factors

• Examination of the scalp and hair

• Magnified scalp imaging

• Baseline photographs

• Discussion of possible contributing factors

• Personalised recommendations for suitable next steps

Where appropriate, we may recommend speaking with your GP about blood tests or further medical investigation. If you already have recent blood-test results, you are welcome to bring them to your consultation.

Our aim is to provide honest, no-pressure guidance. Not every client will require treatment, and not every treatment will be suitable for every person.

Book a Hair and Scalp Consultation

If you have noticed increased shedding, thinning, a widening part or another unexplained change in your hair, a thorough consultation can be a helpful place to begin.

We will take the time to listen, examine your scalp and help you understand the possible next steps.

Request a Hair and Scalp Consultation with Hair Again Clinic.

Important Information

The information in this article is provided for general education only and is not a diagnosis or a substitute for medical advice.

Hair Again Clinic practitioners are not medical doctors. Blood tests must be requested and interpreted by an appropriately qualified healthcare professional. If you are unwell, have unexplained symptoms, suspect a medical condition or are concerned about sudden, patchy or rapidly progressing hair loss, please contact your GP or dermatologist.

Any supplements, medications or treatments should be discussed with your doctor or qualified healthcare professional to ensure they are appropriate for you, particularly if you have allergies, underlying medical conditions, are pregnant or breastfeeding, or take other medications.