Blood Test for Hair Loss: Which Values Actually Tell You Something

What a blood test for hair loss can and cannot answer

A blood test for hair loss checks for the acquired, treatable triggers: iron deficiency, thyroid dysfunction, nutrient gaps and inflammation, less often hormonal or systemic causes. What it can neither confirm nor rule out is pattern hair loss. That form is a clinical diagnosis based on the history, the pattern of loss and trichoscopy, as the dermatological literature consistently describes it.

Two terms recur throughout this article. Androgenetic alopecia is the hereditary form of hair loss, in which follicles at the hairline, the temples and the crown react sensitively to the androgen DHT and gradually shrink. Telogen effluvium is a diffuse hair loss across the whole scalp, in which unusually many follicles shift into the resting phase early at the same time.

The fact that blood values do not capture pattern hair loss does not make the work-up pointless; the opposite is true. Because the hereditary pattern is so common, the treatable share often goes unnoticed. Diffuse hair loss caused by iron deficiency or a thyroid disorder is reversible, and both can be present at once: a hereditary pattern plus an additional diffuse component.

So the pattern decides how much the lab can contribute: diffuse across the whole scalp means the lab leads; a pattern at the hairline and crown means the lab is a side issue; round bald patches or an inflamed scalp mean the dermatologist takes the lead. Which causes may be behind it is covered in the overview of the causes of hair loss .

Is it worth having testosterone or DHT measured?

No, in men with pattern hair loss, measuring testosterone or DHT in serum adds nothing diagnostically. Androgenetic alopecia rests on the sensitivity of the hair follicles to dihydrotestosterone, not on an elevated hormone level in the blood. According to the dermatological literature, affected men usually have normal testosterone and DHT values.

Both conclusions follow from this: a normal value does not rule the diagnosis out, and a high value does not confirm it. In women, by contrast, measuring androgens does make sense, though for a different reason. It looks for an underlying hormonal disorder such as polycystic ovary syndrome, not for the explanation of the hair loss pattern.

Which blood tests for hair loss? The complete overview

The basic panel in hair loss consists of six values: a full blood count with differential, ferritin, CRP, TSH, 25-OH vitamin D and zinc. An extended panel is added when the picture stays unclear or the shedding persists; hormone values and autoimmune serology follow only when the history calls for them. The tables below map out these three tiers, each with what the value shows, when it makes sense and what the typical range looks like.

Tier 1, the basic panel: Full blood count, ferritin, CRP, TSH, 25-OH vitamin D and zinc. This combination covers iron deficiency, anaemia, inflammation, thyroid function and the two nutrient gaps most often discussed. Specialist sources in Germany, the United Kingdom, Italy and Turkey describe it almost identically, which makes it the internationally accepted core of blood testing in hair loss. Whether these tests are done as part of routine care depends on the documented clinical reason rather than on the individual parameter; where that line runs is explained further down in the section on cost and cover.

Tier 2, extended: These values are added when the basic panel is unremarkable but the diffuse hair loss continues, or when a finding still needs explaining. An example from practice: a transferrin saturation below 20 per cent together with a high iron-binding capacity can point to a functional iron deficiency even though ferritin looks ‘normal’.

Tier 3, doctor-indicated: Hormone values and autoimmune serology do not belong in a self-ordered package. They are requested when the history gives a reason, and they are interpreted alongside the clinical picture. A Spanish dermatology journal, Actas Dermo-Sifiliográficas, puts it this way for women: hormone studies, above all where there are additional signs of androgen excess.

More values are not automatically the better approach. A package of 30 parameters mainly produces incidental findings, follow-up tests and costs. National guidance points the same way: the National Institute for Health and Care Excellence deals with vitamin D through targeted supplement use in groups at risk rather than through screening symptom-free adults, and the risk of testing broadly lies less in the blood test itself than in false findings and overdiagnosis. Testing deliberately beats testing broadly.

Diffuse hair loss: which blood values really count here

The decisive blood values in diffuse hair loss are ferritin together with CRP, TSH, 25-OH vitamin D, zinc, vitamin B12 and a full blood count. This is where a blood test delivers the most, because an acquired and often correctable trigger can be behind it. Diffuse means the hair thins across the whole scalp, without a bald spot.

The pattern determines how much the lab can contribute at all. The assignment below is the practical short version of what you may expect from a blood test. Details on the course and on the typical triggers are in the article on diffuse hair loss.

A timeline that is rarely spelled out, and that explains many findings: telogen effluvium typically sets in only two to four months after the trigger, because the affected follicles first remain in the resting phase for several weeks, which on its own lasts around 100 days. So if you are losing hair today, you are looking for an event two to four months ago.

Typical triggers are a feverish infection, surgery, a diet with heavy weight loss, childbirth, significant blood loss or a new medication. An important limitation follows from this: a value measured today may long since be back to normal even though the trigger was real. Once the trigger is gone, the shedding usually settles within three to six months.

A blood test before a hair transplant: why the cause is clarified first

Before a planned hair transplant the blood test serves to draw a line: it should show whether, on top of the hereditary pattern, there is also a diffuse, active hair loss. An ongoing telogen effluvium caused by iron deficiency or an untreated thyroid condition is, from a medical standpoint, a reason to treat that cause first.

The reasoning is straightforward: a transplant relocates hair you already have; it changes neither iron status nor thyroid function. As long as the diffuse component is active, the starting point keeps shifting. The treating doctor decides which values are ordered before a procedure, based on history and findings.

Ferritin in hair loss: the most important and most debated value

Ferritin is the most informative single value in diffuse hair loss, because an iron deficiency can affect the hair before anaemia develops. Ferritin is the storage protein for iron, and the serum ferritin value shows how well the iron stores are filled. With empty stores and no anaemia, haemoglobin is still normal, so a blood count alone stays unremarkable.

The mechanism is easy to follow. Hair follicles are among the most rapidly dividing tissues in the body. Empty iron stores push follicles into the telogen phase prematurely, and the result is a telogen effluvium, that is, diffuse hair loss across the whole scalp. How the phases fit together is explained by the article on the hair growth cycle in detail.

The question of the ‘right’ ferritin value is where things get murky, and precision pays off here. Lab references often define an iron deficiency only below roughly 15 to 30 µg/L, depending on the lab; a value below 15 µg/L is considered highly specific for iron deficiency, provided CRP is unremarkable. That is the well-established part.

The rest is contested. In the specialist debate, a higher target range of roughly 40 to 70 µg/L is put forward for the hair, notably by Rushton (2002) and Trost, Bergfeld and Calogeras (2006), with iron given only after a confirmed deficiency and under medical supervision, because too much iron in the body can cause organ damage and mask an iron storage disorder. Controlled studies such as the one by Olsen and colleagues (2010, Journal of the American Academy of Dermatology), by contrast, found no higher rate of iron deficiency in women with female pattern hair loss or chronic telogen effluvium compared with controls.

It matters where these figures come from: the 40 to 70 µg/L range reflects the position of individual authors, many of them specialising in trichology, and not a guideline recommendation. No major dermatological guideline sets a ferritin target value for the hair. Commercial hair clinics have been quoting the figure as consensus for more than twenty years, although it ultimately goes back to a single piece of work.

On top of that comes an interfering factor that often gets lost in everyday practice. Ferritin is an acute phase protein, that is, a protein whose blood level rises during inflammation. With an infection, inflammation or liver disease the value therefore comes out falsely high. A ferritin of 60 µg/L with a CRP of 12 mg/L can hide a genuine deficiency, which is why CRP is always measured alongside it.

What follows from a low value belongs in a conversation with a doctor, not in self-treatment. The in-depth article on iron deficiency and hair loss explains symptoms, risk groups and the course after supplementation, that is, after the targeted correction of a confirmed deficiency.

Full blood count in hair loss: what it includes and what it misses

A full blood count with differential comprises the basic count, that is, red and white blood cells, haemoglobin, haematocrit, platelets and the red cell indices, plus the differential of the white blood cells. Ferritin, TSH, 25-OH vitamin D and zinc are not included in either type of blood count. Anyone who has only a blood count done for hair loss misses exactly the values that matter for the hair.

That is not an argument against the blood count; it simply does something else. It detects anaemia, and the mean corpuscular volume (MCV) points the way: small cells suggest an iron deficiency, large ones a lack of vitamin B12 or folate. It also gives clues to inflammation and to haematological diseases that call for further work-up.

That leads to a practical rule of thumb for the appointment: instead of asking for ‘a full blood panel’, describe your symptoms and name the values that matter. Ferritin, TSH, 25-OH vitamin D and zinc have to be requested individually, because they are not automatically included in either type of blood count.

Thyroid and hair loss: TSH and when more than TSH is needed

TSH is the baseline value of thyroid testing, and both an underactive and an overactive thyroid can cause diffuse hair loss, because the thyroid hormones T3 and T4 help control the hair cycle. TSH itself is the hormone with which the pituitary gland controls the thyroid. If TSH is abnormal or the clinical suspicion is strong, FT3, FT4 and TPO antibodies follow.

The reference range for adults is often summarised as roughly 0.4 to 4.0 mIU/L, with the upper limit sitting between 3.5 and 5.0 mIU/L depending on the lab. A threshold of 2.5 mIU/L is discussed in parts of the literature as a way to catch a low-normal thyroid function. That is not a hard diagnostic boundary, and a borderline TSH without further signs is not a diagnosis.

In everyday terms, the NHS sets out what an underactive thyroid is and which blood values are used to assess it. Just how common a latent, or subclinical, underactive thyroid really is cannot be stated precisely; cross-sectional epidemiological studies report very different figures, roughly in the range of 3 to 16 per cent, more often in women and at older ages.

TPO antibodies point to Hashimoto’s thyroiditis, an autoimmune condition of the thyroid and the most common cause of an underactive thyroid. A distinction matters here: as part of an autoimmune cluster, Hashimoto’s occurs more often together with patchy hair loss , alopecia areata. That is a patchy and not a diffuse hair loss, and the British Association of Dermatologists publishes separate patient information on the different forms of hair loss and how they are assessed and treated.

One source of interference affects exactly the values at stake here: high-dose biotin from hair and nail supplements distorts immunoassay-based lab tests, thyroid values among them. More on this further down in the section on preparation. What follows from an abnormal value is explained in the article on hair loss and the thyroid .

Vitamin D, zinc, B12 and folate: the nutrient values in the lab

In the lab, the hair-relevant nutrient values are called 25-OH vitamin D, zinc, vitamin B12 or holo-transcobalamin, and folate. The correct parameter name decides how meaningful the result is. What is measured is 25-OH vitamin D, not ‘vitamin D3’. For vitamin B12, holo-transcobalamin, the fraction bound to transcobalamin and therefore available to the cells, is more informative than total B12. Zinc is measured in serum or whole blood and fluctuates over the course of the day.

For vitamin D, the Institute of Medicine classification applies: 50 nmol/L (20 ng/mL) and above is sufficient, 30 to 50 nmol/L is suboptimal, below 30 nmol/L counts as a deficiency. How widespread inadequate levels are depends heavily on the cut-off used and on the season, which is why prevalence figures from different surveys are hard to compare.

Zinc in serum lies roughly between 9 and 21 µmol/L (75 and 140 µg/dL), depending on the method. Because the value fluctuates over the day and drops with inflammation, a single measurement should be read with caution. Folate and vitamin B12 belong to the extended panel, particularly when the blood count shows large red cells.

And the evidence? Honestly, it is inconsistent. A 2019 review by Almohanna, Ahmed, Tsatalis and Tosti in Dermatology and Therapy on the role of vitamins and minerals in hair loss describes the data itself as extensive but in part contradictory. In practice this means: a confirmed deficiency is corrected in a targeted way, while a preventive intake without a deficiency cannot be justified from this evidence.

High intakes carry their own risks. Too much vitamin A or selenium can trigger hair loss, and zinc taken at high doses over a longer period without balancing copper can lead to a copper deficiency. Which nutrients actually matter for the hair is explained in the article on vitamins for hair loss .

Blood values in hair loss in women: hormone profile, cycle and the pill

The blood values in hair loss in women cover the same six basic values as in men: full blood count, ferritin, CRP, TSH, 25-OH vitamin D and zinc. Additional hormone values are a medical decision and are ordered when signs such as cycle disorders, increased facial hair growth, acne or difficulty conceiving are present as well. Testosterone, SHBG, DHEA-S and prolactin then come into consideration, with the selection guided by the clinical picture.

With these values, the timing matters more than the list. Androgens and gonadotropins fluctuate across the cycle, and testosterone additionally follows a daily rhythm with a peak at around 8am. Doctors therefore usually arrange the test for the early follicular phase, around cycle days 2 to 5, and in the morning. Only then are the values comparable at all.

The pill is a real source of interference here. Ethinylestradiol increases SHBG production in the liver, and because only free testosterone, not the fraction bound to SHBG, is biologically active, androgen values on hormonal contraception can only be judged to a limited extent. The literature recommends measuring SHBG alongside and calculating the free androgen index instead of looking at total testosterone alone.

What does not follow from this is that you should stop the pill on your own before a blood test. Whether and when to pause is decided by the doctor treating you, because stopping can itself trigger a temporary diffuse hair loss. This phenomenon is known as post-pill effluvium; there are no reliable figures on how often it occurs.

Stages of life shift the emphasis. After childbirth, postpartum effluvium is in the foreground, and here it is worth looking at ferritin after the blood loss at delivery. During menopause hormonal change and iron status overlap. The broader connection between hormones and hair is explained in a separate article.

One point to close this section: a suspected polycystic ovary syndrome cannot be settled with a hormone package ordered online. It takes a history, an ultrasound scan and a doctor’s overall reading of the values, usually in a gynaecology clinic. A single elevated lab value without that context is more likely to mislead than to help.

The process: how to get a blood test that is actually useful

A GP surgery can take blood just as a dermatology clinic can; for the basic values, the GP is usually the faster route. For the hair-relevant values you do not have to fast; that is mainly needed for blood glucose and blood lipids. What matters is that you describe your symptoms and say which values you want tested.

Biotin interference: pause hair supplements before the blood test

High-dose biotin from hair and nail supplements distorts immunoassay-based lab tests, and with them precisely the thyroid values that are measured in hair loss. The US Food and Drug Administration published a safety communication on this on 28 November 2017, updated in November 2019: thyroid values and the heart attack marker troponin are among those affected, and one death was reported in connection with such interference.

How long beforehand? That depends on the dose. Clinical laboratories consider low-dose multivitamins with 30 to 60 µg of biotin per day harmless, recommend a break of at least eight hours for the 5 to 10 mg per day typical of hair supplements, and at least three days for therapeutic high doses above 10 mg.

Self-tests and online labs are technically an option, and for some people they are the way in to begin with. Without medical interpretation, though, a value stays a number without consequence, and typical sources of interference such as an elevated CRP or biotin intake are often not taken into account. Anyone who takes this route should have the result discussed with a doctor afterwards.

Who goes through the results with me, my GP or a dermatologist?

The results are explained by the practice that ordered them. The hair-specific interpretation, that is, connecting the lab value with the hair picture, is usually done by a dermatology clinic, because the scalp and the pattern are examined there as well. The two complement each other, and neither route is the wrong one.

A practical note on this: take a copy of your results to your next appointment. That prevents the same values being measured twice in quick succession and makes a trend visible. Who plays which role in the work-up is explained in the article hair loss: which doctor can help.

Does the NHS cover a blood test for hair loss?

If there is a medical indication, the basic work-up is usually part of routine NHS care; what counts is the documented clinical reason, not the individual value. So the testing has to have a reason that follows from symptoms and findings. Values requested purely at the patient’s request, without a clinical reason, are normally arranged privately and paid for out of pocket. What a private test costs differs from provider to provider, so it is worth clarifying beforehand.

Where the line runs is not a fixed list but a question of clinical reasoning. In practice, a full blood count, ferritin and TSH are ordered as part of the work-up when a diffuse hair loss is well founded. Extensive vitamin or hormone panels without a concrete clinical suspicion are frequently paid for privately, and ‘hair loss profiles’ are marketed directly to consumers as a paid add-on.

That is why it is worth starting the conversation with the reason rather than with an order list: since when, how severe, diffuse or as a pattern, which accompanying symptoms, which events in the past four months. That is exactly what justifies the test. We deliberately do not quote prices here, because there is no reliable, current source for the individual case.

A second question usually comes up alongside this one: the treatment of pattern hair loss is widely classified as cosmetic and is usually not funded. Products bought from a pharmacy are paid for out of your own pocket in any case. Whether any of it is covered for you is worth clarifying with your GP or your insurer before you start.

Reading blood values correctly: a reference range is not an optimal range

A reference range describes which values occur in the middle 95 per cent of a healthy comparison population. It is a statistical span, not an individual target value. That is why a value can be ‘within the normal range’ and still be too low for your hair, especially at the lower edge of the ferritin range. That explains much of the confusion between what the surgery says and what you read online.

Second, reference ranges depend on the method and on the lab. There is no single universal range, neither for vitamin D nor for zinc or TSH. Comparisons between two labs or with numbers from the internet therefore regularly go wrong. What is reliable is the range printed next to the value on your own report.

Third, a single value is a snapshot. A trend over months says more than one measurement, especially with ferritin and TSH.

Lab report decoder: the abbreviations on your results

The overview below translates the common abbreviations on your lab report, from Hb and MCV to anti-TPO, and says for each one what it has to do with the hair. It is a glossary and not an interpretation of your results: what a specific value means for you belongs in the conversation with your doctor.

All blood values normal and still hair loss: the next steps

Unremarkable blood values are a result and not a failure: they rule out the most common correctable causes and move the question to the pattern. The next step is then not another round of lab tests but the dermatological examination of the scalp. Four explanations cover most of these cases.

What the clinic does instead is not a way of dodging the issue, but the next diagnostic step. Trichoscopy is a digital dermoscopic examination of the scalp that shows hair diameter, follicular openings and signs of inflammation. Added to it are the pull test, standardised photo documentation to track the course and, where there is a suspicion, a scalp biopsy.

One question that comes up almost every time: can stress be detected in the blood? There is no ‘stress value’ that proves stress-related hair loss. Cortisol is not a routine parameter of hair diagnostics and is only measured when there is a concrete endocrinological suspicion. It does not appear in the usual lab panels for hair loss. Whether the amount of hair you are losing is unusual at all is explained in the article on excessive hair loss .

How long does it take for the hair to grow back after a deficiency is corrected?

After a confirmed deficiency has been corrected, the hair loss typically subsides within three to six months; full cosmetic recovery can take 12 to 18 months. The reason is the hair cycle: follicles already in the resting phase still shed before new hairs grow in. That delay is biology, not a sign that treatment has failed.

This timeline is a guide, not a schedule. It is derived from the duration of the hair cycle phases and from the described course of a telogen effluvium. How quickly this happens in an individual case depends on the starting value, on the severity of the deficiency and on whether a pattern hair loss is present as well, which does not respond to correcting a nutrient.

Diffuse or hereditary: what the distinction means in practice

The distinction determines the treatment. A diffuse hair loss across the whole scalp points to an acquired cause and is treated at the root, for example by correcting a confirmed deficiency or by adjusting thyroid treatment. A pattern at the hairline, temples and crown points to the hereditary form, and only this form can respond in the long term to hair growth medication or a hair transplant. Frequently both are present at the same time.

If you are unsure which picture applies to you, the free hair analysis from Elithair gives a first assessment of which pattern is recognisable and what might be worth considering in principle. It is a guide, not a medical diagnosis, and it does not replace a dermatological work-up. Before any treatment, Elithair additionally carries out a blood test to look for causes: if it shows that a deficiency or a hormonal cause is driving the hair loss, that cause is treated first and no transplant is performed. That is the reason we turn down a considerable share of enquiries.

Frequently asked questions about blood values in hair loss

Scientific sources