What Blood Tests Should You Ask for If Your Hair Is Falling Out?

If your hair is falling out more than usual, blood tests can sometimes help identify an underlying cause, particularly iron deficiency or a thyroid condition. But there is no single standard panel of blood tests for hair loss that everyone needs.

The most useful tests depend on what your hair loss looks like, how long it has been happening, your medical history, diet, medicines and any other symptoms. Rather than arriving at your GP appointment with a long shopping list of tests, it is usually better to explain what has changed and ask whether blood tests could help investigate the cause.

The short answer

For diffuse hair shedding, a healthcare professional may consider blood tests to look for iron deficiency and thyroid problems. The British Association of Dermatologists specifically identifies these as possible underlying causes that may be excluded when assessing telogen effluvium, a type of increased shedding from across the scalp.

Depending on your symptoms and history, a clinician may also consider other tests. These might investigate vitamin or nutritional deficiencies, hormonal issues or another suspected health condition.

That does not mean everyone with hair loss needs ferritin, vitamin D, B12, folate, zinc, testosterone and a long list of hormone tests.

Hair loss can often be assessed initially from the history and pattern. The NHS notes that a GP may be able to identify the cause by looking at your hair. Blood tests are useful when there is a reason to suspect something that can be measured in the blood.

Why might you need blood tests for hair loss?

Hair loss is a symptom rather than one single condition.

Some types are primarily diagnosed by their appearance and history. Female pattern hair loss, for example, commonly causes gradual thinning over the top of the scalp and widening of the central parting.

Other hair loss can be triggered by changes elsewhere in the body.

The NHS lists several possible causes of temporary hair loss, including:

illness
stress
cancer treatment
weight loss
iron deficiency

The British Association of Dermatologists also lists childbirth, major illness, surgery, extreme dieting, severe scalp problems, starting certain medicines and stopping hormonal treatment among possible triggers for telogen effluvium.

A blood test cannot detect “hair loss” itself. What it can sometimes do is provide evidence for or against one of the possible underlying causes.

A full blood count can look for anaemia

A full blood count, usually shortened to FBC, measures different types of cells in your blood.

The NHS explains that an FBC can be used to check for blood conditions such as iron deficiency anaemia.

Iron deficiency anaemia happens when the body does not have enough iron to make adequate healthy red blood cells. The NHS lists hair loss as one of its less common symptoms, alongside more familiar symptoms such as tiredness, shortness of breath, palpitations and headaches.

An FBC can therefore be useful if your symptoms or history suggest anaemia.

However, an FBC is not the same as a complete assessment of your iron stores. That is where ferritin may come in.

Ferritin can help assess your iron stores

Ferritin is a protein that stores iron in the body.

A serum ferritin test can help assess how much stored iron you have. You may see ferritin discussed frequently in hair-loss forums because low iron stores have been investigated in relation to diffuse hair shedding.

The British Association of Dermatologists identifies iron deficiency as a possible underlying cause of telogen effluvium and notes that blood testing may be used to exclude it.

Ferritin results still need context. Ferritin can be affected by factors including inflammation and illness, and the meaning of a result can depend on other blood results and your health history.

There is also no universally agreed “perfect ferritin level for hair growth”. Be cautious with exact target numbers presented online as though every person’s hair requires the same ferritin result.

If your ferritin is low, your GP can interpret what that means for you and, importantly, consider why your iron stores may be depleted.

Why iron deficiency is particularly worth checking

Iron deficiency is one of the clearer nutritional links to hair loss.

It can develop because of blood loss, pregnancy or insufficient iron, among other causes. The NHS notes that heavy periods are a common cause of iron deficiency anaemia.

That makes your wider history useful.

Tell your GP if your periods are particularly heavy, you have recently been pregnant, you have digestive symptoms, your diet is restricted, you have experienced significant weight loss or you have previously had low iron.

You do not need to wait until you are certain these things are relevant. They help your clinician decide whether testing is appropriate.

And avoid starting iron simply because your hair is shedding. Too much iron can be harmful, and hair loss may have nothing to do with iron in the first place.

Thyroid blood tests may be appropriate

Thyroid conditions are another recognised possible cause of hair changes.

The thyroid gland produces hormones that affect many processes throughout the body. Both thyroid symptoms and hair loss can develop gradually, which means the connection is not always obvious.

The NHS lists dry hair or hair loss among possible symptoms of an underactive thyroid, alongside symptoms such as fatigue, feeling unusually cold, weight gain, constipation, difficulty concentrating and heavy or irregular periods.

The British Association of Dermatologists specifically notes that blood tests for telogen effluvium may be used to exclude thyroid conditions.

The NHS lists thyroid stimulating hormone, or TSH, as a common blood test used when checking for thyroid conditions. Depending on the clinical situation and result, other thyroid measurements may also be used.

You do not need to decide which thyroid tests to order yourself. Tell your GP about any symptoms that accompany the hair loss and they can decide what is relevant.

Should vitamin D be tested?

Vitamin D is frequently discussed in relation to hair loss, but it is not automatically necessary to test it in everyone whose hair is shedding.

Research has found associations between low vitamin D levels and some forms of alopecia. However, an association does not prove that vitamin D deficiency is causing a particular person’s hair loss or that supplementation will restore their hair.

Whether testing is useful can depend on your symptoms, risk factors, medical history and the type of hair loss being investigated.

There is also separate NHS guidance on vitamin D supplementation for the general population in the UK. That public-health advice should not be confused with treating hair loss.

If you are concerned about vitamin D, ask your GP or pharmacist whether testing or supplementation is appropriate for your circumstances.

What about vitamin B12 and folate?

Vitamin B12 and folate are essential for normal blood formation and other body functions.

Deficiency can cause anaemia and a range of symptoms. A clinician may consider testing them if your history or other blood results suggest a deficiency could be present.

That might be more relevant, for example, if you have a very restricted diet, a condition or medicine that affects absorption, neurological symptoms, or changes on your full blood count.

It does not follow that everyone with hair loss needs B12 and folate testing.

This is a useful general rule for hair-loss investigations: test according to the person, not according to a generic internet checklist.

Do you need a zinc blood test?

Zinc is an essential mineral, and severe zinc deficiency can affect hair.

Research has examined zinc levels in several hair-loss conditions, but zinc testing is not a routine requirement for every person experiencing thinning.

Your GP may consider nutritional deficiencies if your diet, symptoms or medical history make them plausible.

Taking high-dose zinc without evidence that you need it is not a harmless alternative to testing. Excessive zinc can cause side effects and interfere with copper metabolism.

If you already take a hair supplement, check how much zinc it contains before adding another product.

Should hormones be tested for female hair loss?

Not necessarily.

Female pattern hair loss can occur without an obvious hormone abnormality on a blood test. The British Association of Dermatologists describes it as being caused by a combination of genetic and hormonal factors and notes that diagnosis is usually based on the history and pattern of thinning.

Hormonal investigation becomes more relevant when there are other signs that suggest an androgen-related condition.

For example, the BAD notes that female pattern hair loss can accompany conditions where androgen levels are elevated, such as polycystic ovary syndrome, or PCOS. Acne, increased facial hair, irregular periods and fertility difficulties can be signs of PCOS.

If you have hair thinning alongside symptoms such as irregular periods or increased facial or body hair, mention these to your GP. They can decide whether hormonal testing or another assessment is appropriate.

There is little value in ordering a large hormone panel without a clinical reason and then trying to interpret isolated numbers yourself.

What if your blood tests are all normal?

Normal blood tests do not mean that your hair loss is imaginary or that nothing can be done.

Many types of hair loss are not diagnosed through blood tests.

Female pattern hair loss, for example, is generally diagnosed from the history, pattern of thinning and scalp examination. Alopecia areata typically produces characteristic areas of hair loss. Traction alopecia can be related to repeated tension on the hair. Scalp conditions can sometimes be identified during examination.

Telogen effluvium can also occur without an identifiable cause. The British Association of Dermatologists notes that for around one in three people diagnosed with telogen effluvium, no cause is found.

Blood tests are one part of an assessment, not a final verdict on whether hair loss exists.

If shedding or thinning continues despite normal results, go back to your GP. A dermatology assessment may be appropriate if the diagnosis remains uncertain.

The pattern of hair loss can be as useful as the blood tests

Before your appointment, think about how your hair is changing.

Diffuse shedding from across the scalp can point towards a different set of possibilities from a gradually widening parting or distinct bald patches.

Useful details include:

when you first noticed the change
whether it started suddenly or gradually
whether you are shedding more hair or mainly noticing reduced density
whether the loss is all over or concentrated in particular areas
whether you have bald patches
whether your scalp is itchy, painful, red, flaky or otherwise different
whether close relatives have similar hair thinning
any illness, surgery, major stress or childbirth in the months before shedding started
recent weight loss or restrictive dieting
changes to medicines or hormonal contraception
heavy or irregular periods
any new symptoms elsewhere in your body

Telogen effluvium often appears a few months after a trigger, so something that happened earlier in the year may still be relevant even if you felt well by the time the shedding began.

Should you ask your GP for a “hair loss panel”?

You can certainly ask about blood tests, but there is no universal NHS “hair loss panel” that everyone should receive.

A more useful way to frame the conversation is:

“I’ve been losing noticeably more hair for the past few months. Could there be an underlying cause, and would any blood tests be appropriate?”

Then describe the pattern and any other symptoms.

Your GP may decide that checking an FBC, iron status or thyroid function is appropriate. They may recommend different tests based on your circumstances, or they may feel that the pattern itself points towards a diagnosis that does not require extensive blood testing.

This individual approach is more useful than assuming that a longer list of tests automatically means a better investigation.

Should you use private hair-loss blood tests?

Private testing can make a long list of biomarkers look reassuringly thorough, but more tests are not automatically more useful.

A result only helps if there is a sensible reason for measuring it and somebody qualified to interpret it in context.

Testing many nutrients and hormones can also produce borderline or unexpected results that are difficult to interpret without knowing your history, symptoms and the laboratory’s methods.

If you choose private testing, consider who will review the results and what will happen if something is abnormal.

For most people in the UK who are concerned about new hair loss, the NHS recommends seeing a GP first to get an idea of the cause before approaching a commercial hair clinic.

Should you stop supplements before a blood test?

Do not stop prescribed medicines or supplements that have been recommended for a medical reason unless a healthcare professional tells you to.

Instead, tell the person arranging or interpreting your blood tests everything you take, including:

prescription medicines
over-the-counter medicines
multivitamins
hair, skin and nail supplements
individual vitamins and minerals
herbal supplements

This matters because supplements can affect test results or make them harder to interpret.

Biotin deserves particular attention. It is common in hair supplements and high intakes can interfere with certain laboratory tests. If your supplement contains biotin, tell your healthcare professional before testing and follow their instructions.

What happens if a blood test finds something?

That depends entirely on the result.

If iron deficiency is found, the next question is why your iron is low. The NHS explains that iron deficiency anaemia is usually treated with iron replacement while the underlying cause is also addressed where possible.

If thyroid testing suggests a thyroid condition, your GP can arrange the appropriate follow-up and treatment.

If a nutritional deficiency is identified, the solution may involve dietary changes, supplementation or investigation into why the deficiency developed.

Hair recovery can lag behind improvements in blood results because hair follicles cycle slowly. In telogen effluvium, the BAD explains that shedding typically lasts for several months and that it can take additional months for hair volume and thickness to return.

Finding an underlying cause is therefore useful, but it does not mean the appearance of your hair will change immediately.

A simple checklist before your GP appointment

You do not need a spreadsheet of every hair you have shed. A few practical notes are enough.

Before your appointment, you may find it useful to record:

When the hair loss began.
Whether it is shedding, thinning or both.
Where on your scalp you notice it most.
Any illness, surgery, major stress, childbirth or weight change in the previous several months.
Whether your periods are heavy or irregular, if relevant to you.
Any other symptoms such as fatigue, feeling cold, palpitations or unexplained weight change.
All medicines and supplements you currently take.
Any close family history of pattern hair loss.

A few photographs of your parting or hairline taken over time can also help show change, especially if the thinning has been gradual.

When to get professional advice

The NHS advises seeing a GP if you are worried about hair loss.

Make an appointment particularly if:

your hair loss is sudden or unexplained
you are shedding much more than usual
you have distinct bald patches
your parting is progressively widening
your scalp is painful, inflamed, very itchy, scaly or scarred
you have fatigue, breathlessness, palpitations or other symptoms of possible anaemia
you feel unusually cold, have unexplained weight changes or have other possible thyroid symptoms
your periods are very heavy or irregular
you have experienced significant weight loss or follow a very restricted diet
you have signs that could suggest a hormonal condition
you have started or stopped a medicine or hormonal treatment around the time the shedding began
your hair loss is affecting your wellbeing

Do not start high-dose iron, zinc or other supplements simply because hair is falling out. If a deficiency is suspected, appropriate testing can give you much more useful information.

The aim is not to order every blood test available. It is to work out what kind of hair loss you may have and investigate the causes that genuinely fit your situation.

Related reading will be added during editorial review