Hair Loss Blood Tests: Which Tests You Need and What the Results Actually Mean
Medically reviewed by a GMC-registered doctor at The PRP Clinic | Last updated: February 2026
Before you start any hair loss treatment, there is one step that separates genuinely effective care from guesswork: understanding why your hair is falling out. And in most cases, the answer starts with your blood.
Hair loss is rarely caused by a single factor. Genetics play a role, but so do iron levels, thyroid function, hormones, vitamin D status, zinc, B12, and inflammatory markers. Many of these are invisible without testing — you can have iron stores low enough to trigger shedding while feeling perfectly well. You can have a subclinical thyroid imbalance that does not produce obvious symptoms but is slowly thinning your hair.
This is why every patient at The PRP Clinic receives a thorough blood investigation before we recommend any treatment. Without knowing what is happening inside your body, treating hair loss is like trying to fix a car without opening the bonnet. This guide explains which blood tests matter for hair loss, what the results mean, and how they shape an effective treatment plan.
Want to get to the root cause of your hair loss? Our doctors can arrange comprehensive blood testing and interpret your results in the context of your hair health.
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The essential blood tests for hair loss
Ferritin and iron studies
Ferritin is the protein that stores iron in your body, and it is arguably the most important blood marker for hair loss. Iron is essential for hair follicle cell proliferation — without adequate iron, follicles cannot produce healthy hair.
Research published in the Journal of the American Academy of Dermatology has demonstrated that women with hair loss frequently have significantly lower ferritin levels than women with healthy hair. A study in Dermatology and Therapy found that mean serum ferritin levels were approximately 14.7 ng/mL in hair loss patients compared to 25.3 ng/mL in healthy controls.
Here is the critical nuance that many patients (and some GPs) miss: the NHS "normal" reference range for ferritin typically starts at around 12 to 15 ng/mL. But for optimal hair growth, most hair loss specialists recommend ferritin levels between 70 and 100 ng/mL. This means you can receive blood results showing ferritin in the "normal" range but still have levels too low for your hair to thrive.
At The PRP Clinic, we interpret ferritin results specifically in the context of hair health, not just against standard reference ranges.
Full blood count (FBC)
A full blood count measures red blood cells, white blood cells, haemoglobin, haematocrit, and platelets. It helps identify anaemia (a common cause of diffuse hair shedding), signs of infection or inflammation, and overall health markers that may indirectly affect hair growth.
Approximately 25-30% of people experiencing hair loss have some degree of anaemia when properly investigated. Iron-deficiency anaemia is particularly common in women with heavy menstrual periods.
Thyroid function tests (TSH, Free T3, Free T4)
Thyroid hormones directly regulate the hair follicle cycle. Both hypothyroidism and hyperthyroidism can cause diffuse hair thinning or shedding. Approximately 15% of hair loss patients have an underlying thyroid disorder.
TSH (thyroid-stimulating hormone) is the standard screening test. However, a complete picture requires measuring Free T3 and Free T4 as well, because subclinical thyroid dysfunction — where TSH is borderline but T3/T4 are slightly off — can manifest as hair thinning even before other thyroid symptoms become obvious.
In some cases, thyroid autoantibodies (anti-TPO, anti-thyroglobulin) may also be relevant, as autoimmune thyroid conditions frequently correlate with alopecia areata and diffuse hair loss.
Vitamin D (25-hydroxyvitamin D)
Vitamin D plays an important role in the hair growth cycle. Research has shown that vitamin D levels below 30 ng/mL are significantly associated with various forms of alopecia, including androgenetic alopecia and telogen effluvium.
Vitamin D deficiency is remarkably common in the UK due to limited sunlight exposure, and many hair loss patients are found to have suboptimal levels. Correcting vitamin D deficiency through supplementation can meaningfully support hair regrowth, particularly when combined with other treatments.
Sex hormones (testosterone, DHEAS, SHBG)
Hormonal imbalances are a major driver of hair loss in both men and women. Dihydrotestosterone (DHT) — a metabolite of testosterone — is the primary hormone responsible for follicle miniaturisation in androgenetic alopecia.
Testing testosterone, DHEAS (dehydroepiandrosterone sulfate), and SHBG (sex hormone-binding globulin) helps identify whether elevated androgens are contributing to your hair loss. In women, this testing is particularly important as it can also reveal conditions like polycystic ovary syndrome (PCOS), which frequently presents with hair thinning alongside other symptoms.
Vitamin B12 and folate
Vitamin B12 and folate are essential for healthy cell division, including the rapidly dividing cells of hair follicles. Deficiency in either can contribute to hair thinning, premature greying, and poor hair quality. B12 deficiency is common in those following plant-based diets, older adults, and people with certain digestive conditions.
Zinc
Zinc is a trace mineral with a documented role in hair follicle health. It supports the protein structures that make up the hair shaft and plays a role in the oil glands surrounding follicles. Low zinc levels have been associated with telogen effluvium and alopecia areata. Zinc is not always included in standard NHS blood panels, which is why specialist testing matters.
Inflammatory markers (CRP)
C-reactive protein (CRP) is a marker of systemic inflammation. Elevated CRP can indicate an inflammatory or autoimmune component to hair loss — relevant in conditions like alopecia areata, lupus-related hair loss, or chronic scalp inflammation.
Blood testing is the foundation of effective hair loss treatment. Without it, you are guessing. With it, we can build a precise, personalised plan.
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Why standard NHS tests may not be enough
Your GP can certainly order basic hair loss blood tests — and we encourage you to start there if cost is a concern. However, there are limitations to be aware of.
NHS blood panels typically cover full blood count, ferritin, TSH, and sometimes vitamin D. They may not routinely include DHEAS, SHBG, detailed hormonal profiles, zinc, or comprehensive thyroid panels (Free T3, Free T4, antibodies). Reference ranges used by NHS laboratories are designed to identify clinical disease — they may not flag suboptimal levels that are still affecting your hair.
Perhaps most importantly, GPs are generalists. They interpret blood results in the context of your overall health, which is entirely appropriate. But interpreting results specifically in the context of hair loss — understanding which ferritin level is "normal" versus "optimal for hair growth," for example — requires specialist knowledge.
At The PRP Clinic, our doctors order targeted panels based on your individual presentation and interpret every result through the lens of hair health and regenerative medicine. This is the level of investigation that allows us to build truly personalised treatment plans.
How blood test results shape your treatment plan
Blood testing is not a standalone exercise — it is the diagnostic foundation that determines everything that follows.
If we identify low ferritin or iron-deficiency anaemia, we address this through targeted supplementation before or alongside regenerative treatments. PRP and exosome therapy work best when your body has adequate iron to support new hair growth.
If thyroid dysfunction is detected, we can recommend appropriate medical management (or liaise with your GP or endocrinologist) to correct the imbalance, which is essential before expecting hair treatments to work effectively.
If hormonal imbalances are found, this shapes both the treatment approach and the prognosis. Understanding your hormonal profile helps us set realistic expectations and choose the most appropriate combination of treatments.
If vitamin or mineral deficiencies are identified, our doctors design personalised supplement protocols to correct these specifically. This is not generic multivitamin advice — it is targeted, evidence-based supplementation based on your actual blood levels.
This is the holistic, doctor-led approach that defines The PRP Clinic. We treat the whole picture, not just the surface symptom.
Frequently asked questions about hair loss blood tests
What blood tests should I get for hair loss?
A comprehensive panel includes ferritin, full blood count, thyroid function (TSH, Free T3, Free T4), vitamin D, vitamin B12, folate, zinc, sex hormones (testosterone, DHEAS, SHBG), and inflammatory markers (CRP).
What ferritin level causes hair loss?
Ferritin below 30 ng/mL can trigger shedding. For optimal hair growth, specialists recommend 70-100 ng/mL. NHS "normal" ranges may not reflect the level needed for healthy hair.
Can thyroid problems cause hair loss?
Yes. Both hypothyroidism and hyperthyroidism cause diffuse hair thinning. About 15% of hair loss patients have a thyroid disorder.
Can the NHS do blood tests for hair loss?
GPs can order basic panels (FBC, ferritin, TSH, vitamin D). Specialist clinics can arrange more comprehensive panels and interpret results specifically for hair health.
Why do I need blood tests before PRP?
PRP stimulates follicles, but if your body lacks essential nutrients (iron, vitamin D, zinc), the treatment cannot reach its full potential. Correcting deficiencies alongside PRP produces significantly better outcomes.
How long does it take to get results?
Most blood test results are available within 3 to 5 working days. Your doctor will review results with you and explain what they mean for your hair and your treatment plan.
Start with answers, not assumptions
Hair loss treatment that works starts with understanding why your hair is falling out. Blood testing gives us the answers. From there, we can build a treatment plan that addresses every contributing factor — from targeted supplementation to advanced regenerative treatments like PRP and exosomes.
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This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment.
