Losing More Hair Than Usual? 6 Blood Markers That Can Reveal Why

You notice it in the shower drain first. Then on your pillow, your brush, the floor of the bathroom. Your ponytail feels a little thinner and your parting looks a little wider. Most people reach for a new shampoo or a hair oil. But very often the real answer is not on your scalp at all. It is in your blood.

In this Care Guide, I explain how much hair loss is normal, which blood markers are worth checking, what the numbers mean, and what to expect once the cause is found.

What Is a Hair-Loss Blood Assessment?

A hair-loss blood assessment is a targeted set of blood tests chosen after a consultation and scalp examination. Its purpose is to find, or rule out, internal causes of shedding that no topical product can fix, such as low iron stores, vitamin D deficiency, a thyroid imbalance, hormonal changes or insulin resistance.

It is not a treatment in itself. It is the step that makes treatment make sense. Treating hair loss without knowing why it is happening is a little like painting over a damp wall.

The Science: How Much Hair Loss Is Normal?

Every hair follicle runs through a cycle. The growth phase (anagen) lasts roughly 2 to 7 years. A short transition phase (catagen) follows, and then a resting phase (telogen) of around three months, after which the hair is shed and a new one starts to grow.

This is why losing around 50 to 100 hairs a day is considered normal. It becomes a concern when shedding is clearly more than usual, or when you see thinning: a wider parting, a smaller ponytail, more scalp showing under bright light, or receding temples.

Hair follicles are among the fastest-dividing cells in the body, so they are sensitive to what is happening inside it. A shortage of iron, a slow thyroid or a hormonal shift can push more follicles into the resting phase at once. This type of shedding, called telogen effluvium, typically appears 2 to 3 months after the trigger. That delay is why people rarely connect it to the illness, crash diet, stressful period or pregnancy that started it.

How It Works: The 6 Blood Markers Worth Checking

These are the markers I most often consider. Not everyone needs every test; your history and examination decide which are relevant.

1. Ferritin: Your Iron Stores

Ferritin reflects how much iron your body has in storage. It can be low even when your haemoglobin is normal, meaning you are not anaemic yet but your reserves are running low. Low iron stores are one of the most common, and most correctable, contributors to shedding. This is especially true in women with heavy periods, vegetarians and people who have lost weight quickly.

• Low: below 30 ng/mL
• Normal (women): approx. 30–150 ng/mL
• Normal (men): approx. 30–400 ng/mL

Ferritin also rises with inflammation, so it is read alongside a full blood count. Please do not start high-dose iron on your own, because too much iron is harmful too.

2. Vitamin D (25-OH)

Vitamin D plays a role in the hair cycle. Low levels have been linked with telogen effluvium, female pattern hair loss and alopecia areata. These are associations rather than proof that low vitamin D causes hair loss. Even so, deficiency is common and worth correcting, even in sunny Dubai, where many people spend most of the day indoors.

• Deficient: below 20 ng/mL
• Insufficient: 20–29 ng/mL
• Sufficient: 30–100 ng/mL

3. Thyroid: TSH and Free T4

Both an underactive and an overactive thyroid can cause diffuse thinning. There are often other clues too, such as tiredness, weight change, feeling cold or hot, or changes in the skin and nails.

• TSH: approx. 0.4–4.0 mIU/L
• Free T4: approx. 0.8–1.8 ng/dL

Once thyroid levels are corrected, hair usually recovers, but it takes months rather than weeks.

4. Zinc

Zinc supports keratin production and the rapid cell division that hair growth depends on. Deficiency is more likely with restrictive diets, digestive conditions or after weight-loss surgery.

• Low: below 70 µg/dL
• Normal: approx. 70–120 µg/dL

Zinc is best measured on a fasting morning sample. Taking excess zinc long term can cause copper deficiency, so supplementation should be guided by your result.

5. Androgens: Testosterone, SHBG and DHEA-S (Mainly Women)

In women, thinning over the crown together with acne, irregular periods or excess facial hair can point to raised androgen activity. The most common cause is polycystic ovary syndrome (PCOS).

• Total testosterone (women): approx. 15–70 ng/dL
• SHBG (women): approx. 18–144 nmol/L
• DHEA-S: age- and sex-specific; read against your lab’s range

Myth: High testosterone makes men go bald.
Truth: Most men with male pattern hair loss have normal testosterone levels. The key driver is genetically sensitive follicles reacting to DHT, a by-product of testosterone. That is why a normal hormone panel does not rule out pattern hair loss.

6. HOMA-IR: Insulin Resistance

HOMA-IR is calculated from your fasting glucose and fasting insulin. A raised value suggests insulin resistance. Insulin resistance tends to lower SHBG, which leaves more free androgen available at the follicle. It is common in PCOS and has also been associated with early pattern hair loss in some studies.

• Normal: below 2.0
• Borderline: 2.0–2.5
• Insulin resistance likely: above 2.5

Cut-offs vary between laboratories. The good news is that insulin resistance responds well to nutrition, activity, sleep and, where appropriate, medically supervised weight management.

Depending on your history, I may also add a full blood count, vitamin B12, folate or prolactin.

Benefits of Testing Before Treating

• You treat the cause, not just the symptom. Correcting a deficiency can settle shedding where shampoos and serums cannot.
• You avoid guesswork with supplements. Taking iron, zinc or high-dose vitamins you do not need can be harmful.
• You pick up wider health issues early. Thyroid disease, PCOS and insulin resistance matter far beyond your hair.
• Clinic treatments work better. Hair treatments are more likely to help once internal causes are corrected.
• You get a baseline. Repeat testing shows whether the plan is working.

Side Effects and Limitations

A blood test is a low-risk procedure. You may have brief discomfort, minor bruising or, occasionally, feel light-headed. The more important points are the limitations:

• Normal results do not mean nothing is wrong. Pattern hair loss and alopecia areata can occur with completely normal bloods.
• Reference ranges differ between labs and often depend on age and sex.
• “Optimal” numbers on social media are not always evidence-based.
• Some supplements distort results. High-dose biotin, common in hair vitamins, can interfere with thyroid and hormone tests.

Results: What to Expect

Hair recovers slowly because of the hair cycle. Once a trigger is corrected, shedding typically begins to settle over about 3 to 6 months. Visible regrowth and density take 6 to 12 months. Scalp hair grows roughly 1 cm a month, so patience is genuinely part of the treatment.

Your plan may include correcting deficiencies, managing thyroid or hormonal conditions, nutrition and lifestyle changes, and medical treatments for hair. For suitable patients, in-clinic options such as PRP for hair may also be discussed. Responses vary from person to person, and no treatment can guarantee a specific result.

What to Know Before Your Blood Test

• Fast for 8 to 10 hours (water is fine) if HOMA-IR or glucose is being checked.
• Book a morning appointment. Zinc and testosterone are best measured in the morning.
• Pause biotin for 2 to 3 days beforehand, after checking with your doctor.
• Bring your medication and supplement list, and any previous blood results.
• Note the timeline: when the shedding started, and anything that happened 2 to 3 months before it.

When to See a Doctor Sooner

Book an assessment promptly if you notice any of these:

• sudden or patchy hair loss
• loss of eyebrows or eyelashes
• scalp pain, redness or scaling
• hair loss together with fatigue, unexplained weight change or irregular periods

Frequently Asked Questions

Can I just take a hair supplement instead?
Supplements help when you are actually deficient. If you are not, they are unlikely to help, and some can cause harm or interfere with test results.

Is a home blood test kit enough?
It can be a starting point, but results still need interpreting alongside your history and a scalp examination.

My bloods were normal last year. Should I repeat them?
If your shedding is new or has changed, yes. Iron, vitamin D and thyroid levels can change within months.

Book Your Hair-Loss Assessment

If you are counting strands every morning, it is time to stop guessing. I offer a doctor-led hair-loss assessment: consultation, scalp examination, a targeted blood panel and a personalised plan built around your results.

Book your consultation at drpravinkumar.com or message me on Instagram @drpravinkumar_dubai.

Dr Pravin Kumar, General Practitioner (DHA-licensed)

Reference ranges are typical adult values and vary by laboratory, age and sex. This article is for general education and is not a substitute for personal medical advice. Individual results vary.