Blood tests for hair loss


Blood tests are the single highest volume medical activity, making it prudent to ask how well a given test result (that is high, low, or normal) can define the health status of an individual who is suffering from hair loss.

Blood is a connective tissue and a conduit for many nutrients and minerals, but it can not give any indication of the levels of vitamins, minerals or haemoglobin that is within the tissue of interest e.g. the hair follicle.  This means that even ‘normal’ results must be evaluated somewhat sceptically by a trichologist or doctor when hair loss occurs.


(and what to do about it)


B12 is one of the eight B vitamins and is involved in the metabolism of absolutely every cell in your body.  It used to be known as the “maturation factor” because all cells in the body require vitamin B12 to mature into fully functioning cells.

Early studies looking at the function of B12 showed that blood cells in the bone marrow that were initially deprived of vitamin B12 could mature within a few hours of exposure to B12.  This explains why some patients feel rejuvenated within days of their first B12 injection [1].

B12 levels in the blood tend to fall late in deficiency, meaning the deficiency will be present for possibly months before it is reflected in the blood.  In addition to this, new Chemiluminescence technologies measure total serum B12 without considering the fact that around 80% of B12 circulates in a biochemically inert form.

What to do: A better test for B12 deficiency is to measure blood levels of methylmalonic acid (MMA) as this will show the first sign that you have low levels of B12. You can show a normal B12 level, but if MMA is elevated, then B12 deficiency is inevitable.  Alternatively, testing for ‘active’ B12 rather than ‘total’ will give a clearer indication of available B12.


A study investigating the role of vitamin D in female hair loss showed a direct correlation with the levels of vitamin D and hair loss. Whilst vitamin D deficiency is classed at a value below 25 nmol/L, the study revealed that all the participants that took part in the hair loss group had levels of vitamin D below 75 nmol/L.  The blood vitamin D2 level in cases of thinning hair and excess shedding ranged from 11.5 to 74.4 nmol/l with an average of 28.8 nmol/l, while in female pattern hair loss cases, it ranged from 12.7 to 62 nmol/L with an average of 29.1 nmol/L [2].

A separate study found vitamin D levels were lower in women with alopecia areata.  The concentrations of vitamin D were found to be below 50 nmol/L in 85% of patients with alopecia areata.  There was no correlation with the levels of vitamin D and various clinical parameters, including extent of the hair loss patch, disease duration, number of patches, and nail involvement [3].  Low levels of vitamin D also correlate to low levels of zinc.  As zinc is a major indicator of haemoglobin, a complete CBC and zinc panel are recommended.  Low vitamin D also correlates with high level of hepcidin (iron inhibitory hormone).

What to do: If your vitamin D levels are below 75 nmol/L, you can supplement with vitamin D, until it is within the desired range.  Request a CBC and zinc panel from your doctor or trichologist.


Ferritin is a blood protein that binds iron, essentially holding this highly reactive ion in storage. A ferritin test evaluates how much iron you have in storage and high or low results may, or may not, be cause for concern.  In normal circumstances, ferritin levels are a sensitive and accurate marker for iron status, but ferritin is an acute phase reactant that is elevated in response to inflammation, complicating the diagnosis.

In simpler terms, if there are other factors present, such as chronic inflammation, infections or autoimmune disorders, the ferritin test result will be unreliable and will not give an accurate reflection of iron stores. Even moderate exercise caused an increase in plasma ferritin concentration, with the increase being greater as the intensity and duration of exercise increased.  This makes ferritin an unreliable biomarker for hair loss.

What to do: When investigating iron status, also look at serum iron and total iron binding capacity, and transferrin saturation.


When we’re stressed, or have irregular eating patterns or a lack of quality sleep, our adrenal glands produce a hormone called cortisol, and then the cortisone signals our hair follicles to shift from the growth phase, and into resting phase: meaning this hair will shed prematurely.

High levels of cortisol in the body can also be a reaction to uncontrolled inflammation within the body.  To assess cortisol levels, often a saliva test or blood test is taken in the morning to assess whether cortisol is within the normal range: cortisol is always higher in the morning.  What is vitally missing with this kind of test is a follow up throughout the day to check that cortisol levels drop as they are expected to.

What to do: Get a 12-hour cortisol test that lets you collect saliva samples throughout the day, giving you an accurate representation of your cortisol levels.


Blood tests are often offered to patients with hair loss and an overwhelming majority come back with inconclusive results.  With little in the way of definitive serum ranges and an inconsistency in patient findings, it is clear that blood tests are not very sensitive in the diagnosing hair loss and offer little prognostic value.


  1. 1. Edelberg D. B12 Deficiency: Still America’s #1 Missed Diagnosis – WholeHealth Chicago [Internet]. WholeHealth Chicago. 2020 [cited 31 March 2020]. Available from:
  2. EOhnemus U, Uenalan M, Inzunza J, Gustafsson JA, Paus R. The hair follicle as an estrogen target and source. Endocrine reviews. 2006 Oct 1;27(6):677-7Rasheed H, Mahgoub D, Hegazy R, El-Komy M, Hay RA, Hamid MA, Hamdy E. Serum ferritin and vitamin d in female hair loss: do they play a role?. Skin pharmacology and physiology. 2013;26(2):101-7.
  3. Yilmaz N, Serarslan G, Gokce C. Vitamin D concentrations are decreased in patients with alopecia areata. Vitam Trace Elem. 2012;1(3):105-9.