What Your Blood Test Can Reveal About Hair Thinning

“Why do I need a blood test for hair loss?”

It’s a fair question. After all, when we notice our hair thinning or falling out more than usual, our first instinct is often to change our shampoo, try a hair tonic, or browse online for supplements. But what many don’t realise is that hair loss isn’t just a surface-level issue. It can be a visible sign of internal imbalances, nutritional deficiencies, hormonal shifts, or even underlying health conditions.

That is why at Terra Medical Clinic, we take a holistic approach to treating hair thinning. That starts with understanding why it’s happening, because only then can we choose the right path forward. One of the most effective tools in our diagnostic toolkit is the blood test.

In this article, we’ll explain why blood testing is so important for uncovering the root causes of hair loss, what specific markers we look for, and how the results guide your personalised treatment plan.

Hair Loss: More Than Skin Deep

To understand how internal health affects your hair health, let’s first look at how hair grows. Hair growth might seem like a simple, straightforward process. But it’s a highly regulated biological cycle [1] that repeats itself continuously. What most people don’t know is that hair doesn’t grow all at once – instead, it moves through distinct phases.

The phases are:

• Anagen (growth phase) – lasts between 2 to 6 years as the hair grows actively from the follicle.
• Catagen (transition phase) – a short phase lasting a few weeks where hair growth slows, and the follicle begins to shrink. 
• Telogen (resting or shedding phase) – lasts a few months as old hairs are shed to make room for new ones.

At any given time, approximately 85 to 90% [2] of scalp hairs are in the anagen phase, while the remaining 10 to 15% [3] are in the catagen or telogen phase. However, various internal factors can disrupt this cycle. This causes hair to prematurely enter the telogen phase (shedding phase) or impair the ability of follicles to produce new, healthy strands.

If you’re noticing increased hair fall, hair thinning at the temples or crown, or a loss of overall volume, these are signs that your hair cycle may be disrupted. This is where a blood test comes in, as it helps us to explore what might be triggering these changes.

 

What Can a Blood Test Reveal?

Rather than guessing the cause of your hair loss, blood testing allows us to measure what’s happening inside your body. It provides a scientific basis for diagnosis, ruling out or confirming potential causes, and shaping a treatment strategy tailored to your needs.

Let’s look at the most common markers we assess:

Nutritional Deficiencies

One of the most frequent and treatable causes of hair thinning is micronutrient deficiency [4]. Hair is a non-essential tissue from a survival perspective, meaning your body will divert nutrients to more vital organs when resources are limited.

Some of the common nutrients linked to hair loss include:

• Iron (especially Ferritin) – Serum Ferritin levels are a reliable indicator of your body’s iron storage. Low levels are strongly associated with chronic hair shedding [5], particularly in women with heavy menstrual cycles or vegetarian diets. Hair follicles require iron to generate new cells rapidly.
• Vitamin B12 – Plays a crucial role in red blood cell formation [6] and energy metabolism. A deficiency can lead to fatigue, pale skin, and hair thinning. It’s especially common in people with poor gut absorption or on vegan diets.
• Vitamin D – more than just a bone health vitamin, ‘D’ is also a hormone that affects the hair follicle cycle [7]. Low levels are linked to telogen effluvium (diffuse shedding) and even autoimmune conditions like alopecia areata.
• Zinc – zinc supports tissue repair, oil gland function, and follicle health [8]. It also plays a role in the activity of enzymes and immune function. Zinc deficiency may lead to brittle hair, increased shedding, or scalp irritation.

Correcting these deficiencies doesn’t just improve hair. It can boost energy, skin quality, and overall well-being. Blood testing helps us to pinpoint what’s lacking, so we can recommend precise supplements or IV nutrition where appropriate.

Thyroid Function

Thyroid disorders are a common yet often overlooked cause of hair thinning, especially in women.

Your thyroid gland produces hormones that regulate metabolism, cellular turnover, and protein synthesis. All of this affects hair growth and its cycle. Both underactive and overactive thyroid conditions can contribute to noticeable hair changes.

 

Through a blood test, we will be able to:

TEST	PURPOSE
Thyroid-stimulating Hormone (TSH)	Measure the brain’s signal to the thyroid. Help detect under- or overactivity.
Free T3 and Free T4	Assess levels of active thyroid hormones in circulation.
Thyroid Antibodies (if needed)	Checks for autoimmune thyroid conditions such as Hashimoto’s disease.

 

Once we have obtained your results, we will have a more comprehensive understanding of your hair loss, such as:

 

CONDITION	EFFECT ON HAIR	OTHER COMMON SYMPTOMS
Hypothyroidism	Thinning, dry, and brittle hair due to slowed follicle activity.	Cold intolerance. Fatigue. Weight gain.
Hyperthyroidism	Diffuse hair shedding is linked to accelerated hair cycle turnover.	Anxiety. Palpitations. Unintended weight loss.

 

Thyroid-related hair loss typically won’t improve until the underlying hormonal imbalance is treated. That’s why identifying it early through blood testing is crucial.

Hormonal Imbalances

Hormones have a profound influence on hair. If you’ve noticed changes during puberty, pregnancy, or menopause, or if your hair seems to follow a male or female pattern of thinning, then maybe hormonal shifts may be at play.

A blood test can help us assess key hormones, such as:

• Testosterone and DHEA-S – androgens (male hormones) are present in both sexes. Excessive levels can shrink hair follicles [9] and shorten the growth phase.
• Free and Total Testosterone – free testosterone is the active form and can be converted into dihydrotestosterone [10] (DHT), a key player in androgenetic alopecia.
• Estrogen and Progesterone – estrogen and progesterone are especially relevant in women. In fact, drops in oestrogen after childbirth or during menopause may lead to noticeable hair thinning [11].
• Follicle-stimulating (FSH) and luteinising hormones (LH) – FSH and LH are hormones that govern menstrual and reproductive cycles. Imbalances may indicate polycystic ovarian syndrome [12] (PCOS), which is a common cause of hormonal hair loss.

But how do hormonal imbalances affect your hair? In men, high DHT levels lead to a receding hairline or thinning at the crown. Meanwhile, androgen sensitivity in women can lead to thinning along the part line or diffuse shedding.

The good news is that hormonal hair loss often responds well to targeted treatments, such as DHT blockers, hormone balance, or low-dose oral medications. But without knowing your hormonal profile, it’s difficult to choose the right intervention.

Autoimmune Markers

If your hair loss is sudden, patchy, or occurs in small circular spots, an autoimmune condition might be involved. In autoimmune hair loss, the body mistakenly targets its hair follicles.

Some of the common autoimmune markers that are assessed through a blood test are:

• Antinuclear Antibody (ANA) – a broad screening test for autoimmune conditions.
• Erythrocyte Sedimentation Rate (ESR) and C-reactive protein (CRP) – ESR and CRP are markers that detect inflammation in the body.
• Specific Antibodies – depending on the symptoms, further tests may be ordered to investigate conditions like lupus or alopecia areata.

 

Autoimmune-related hair loss requires a different treatment approach. Anti-inflammatory or immunomodulating therapies might be necessary to calm the immune system and protect your hair follicles. In certain cases where autoimmune diseases are detected through blood tests, we may refer you to a relevant specialist, like a rheumatologist or dermatologist, with expertise in autoimmune conditions, for further evaluation and targeted treatment.

Other Health Markers

Beyond nutrient and hormone levels, there are general health indicators that can impact hair quality:

• Blood Sugar and Insulin – insulin resistance, commonly seen in PCOS, can contribute to androgen excess.
• Inflammatory Markers – persistent low-grade inflammation may interfere with hair follicle function or signal an underlying chronic illness.
• Liver and Kidney Function – these organs are essential for detoxification and nutrient metabolism. Impairments may indirectly lead to hair thinning.

 

How Terra Medical Responds

So, how do we turn test results into real solutions? Each blood test finding helps us tailor treatments that target the root cause of your hair loss, not just the symptoms.

It’s important to note that, in certain circumstances, when test results point to underlying issues and broader medical conditions, we may involve other doctors with expertise in other medical specialties — this can include gynaecology, endocrinology or rheumatology, depending on condition. A multidisciplinary approach ensures that every aspect of your health is addressed, allowing for more targeted and effective treatment for your hair loss. 

 

Disclaimer it – This information is intended as a general guide only and should not be considered medical advice from Terra Medical Clinic. Please consult a certified doctor for a proper evaluation of any medical concerns, including blood test results.

Why Testing Matters: Personalised, Not One-Size-Fits-All

Hair loss can be distressing, but it’s also highly individual. Two patients with the same symptoms may have entirely different causes. That’s why guessing or self-medicating rarely brings lasting results.

More importantly, we believe in science-backed personalisation. With a blood test, the results will provide clear insights that guide precise, effective treatment tailored to you.

Other benefits may include:

• Clarity – clear answers about what’s happening internally.
• Confidence – reassurance that your hair loss is being treated with precision, not assumptions.
• Direction – a roadmap for targeted treatments that address the cause, not just the symptoms.

Whether you’re facing female pattern hair loss, chronic telogen effluvium, postpartum shedding, or hair thinning with no clear cause, knowing the “why” is the first step toward sustainable improvement.

 

What to Expect: The Patient Journey

Wondering what the process involves? Don’t worry! It’s straightforward, supportive, and designed with your comfort in mind. Rest assured that we will walk with you every step of the way.

To give insight, here’s what a typical patient journey looks like:

• Initial Consultation – we take time to understand your hair concerns, medical history, and lifestyle factors. Scalp imaging and density assessments may also be made.
• Blood Testing – if indicated, we’ll arrange for a blood draw in-clinic or at a nearby lab. It usually takes 5 to 10 minutes and requires minimal preparation.
• Results Review and Interpretation – once your results are in, we sit down with you to explain what they mean in plain terms. No jargon, just insights.
• Customised Treatment Plan – based on your profile, we create a treatment plan tailored to your goals, comfort level, and lifestyle.
• Ongoing Support – hair restoration is a journey, not a quick fix. We walk with you every step of the way, adjusting treatments as needed and tracking your progress over time.

 

Final Thoughts

Hair thinning can feel frustrating, even disheartening. But it doesn’t have to be a mystery. A blood test offers clarity, answers, and a path forward. By understanding what’s going on inside your body, you give yourself optimal chances of regaining not just hair, but confidence, vitality, and peace of mind.

At Terra Medical Clinic, our clinical team is here to help you uncover the cause and take meaningful steps toward healthier, stronger hair. So, are you ready to take the first step? Then contact us to book a detailed consultation and personalised treatment plan. 

References

1. Natarelli, N., Gahoonia, N., & Sivamani, R. K. (2023). Integrative and Mechanistic Approach to the Hair Growth Cycle and Hair Loss. Journal of clinical medicine, 12(3), 893. https://doi.org/10.3390/jcm12030893
2. Jimenez, F., & Alam, M. (2024). The Proportion of Catagen and Telogen Hair Follicles in Occipital Scalp of Male Androgenetic Alopecia Patients: Challenging the Established Dogma. In Experimental Dermatology (Vol. 33, Issue 10). Wiley. https://doi.org/10.1111/exd.70001
3. Jimenez, F., & Alam, M. (2024). The Proportion of Catagen and Telogen Hair Follicles in Occipital Scalp of Male Androgenetic Alopecia Patients: Challenging the Established Dogma. In Experimental Dermatology (Vol. 33, Issue 10). Wiley. https://doi.org/10.1111/exd.70001
4. Almohanna, H. M., Ahmed, A. A., Tsatalis, J. P., & Tosti, A. (2019). The Role of Vitamins and Minerals in Hair Loss: A Review. Dermatology and therapy, 9(1), 51–70. https://doi.org/10.1007/s13555-018-0278-6
5. Abbaspour, N., Hurrell, R., & Kelishadi, R. (2014). Review on iron and its importance for human health. Journal of research in medical sciences : the official journal of Isfahan University of Medical Sciences, 19(2), 164–174. 
6. Iron deficiency anaemia. (2017). In nhs.uk. https://www.nhs.uk/conditions/iron-deficiency-anaemia/
7. Cedirian, S., Prudkin, L., Santana, J. A., Piquero-Casals, J., Saceda-Corralo, D., & Piraccini, B. M. (2025). The exposome impact on hair health: non-pharmacological management. Part II⋆. In Anais Brasileiros de Dermatologia (Vol. 100, Issue 2, pp. 322–327). Elsevier BV. https://doi.org/10.1016/j.abd.2024.08.006
8. Kil, M. S., Kim, C. W., & Kim, S. S. (2013). Analysis of serum zinc and copper concentrations in hair loss. Annals of dermatology, 25(4), 405–409. https://doi.org/10.5021/ad.2013.25.4.405
9. DHT (dihydrotestosterone) and its link to hair loss. (2017). In www.medicalnewstoday.com. https://www.medicalnewstoday.com/articles/68082
10. DHT (dihydrotestosterone) and its link to hair loss. (2017). In www.medicalnewstoday.com. https://www.medicalnewstoday.com/articles/68082
11. Rinaldi, F., Trink, A., Mondadori, G., Giuliani, G., & Pinto, D. (2023). The Menopausal Transition: Is the Hair Follicle “Going through Menopause”?. Biomedicines, 11(11), 3041. https://doi.org/10.3390/biomedicines11113041
12. Shukla A, Rasquin LI, Anastasopoulou C. Polycystic Ovarian Syndrome. [Updated 2025 May 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459251/