Blood Tests for Hair Loss:

What to Check, Why It Matters & How to Interpret Results for Hair Health

When it comes to diagnosing hair loss, blood tests are one of the most valuable tools we have, but only if we know what to look for and how to interpret the results in the context of hair biology, not just essential survival.

Hair is considered a non-essential tissue, meaning the body will prioritise other organs and systems before sending nutrients to the hair follicle. This is why ‘normal’ blood test results may still reflect suboptimal levels when it comes to hair growth.

In this guide, I’ll take you through:

• The key blood tests for different types of hair loss

• What levels are optimal (not just within reference range)

• Nutrient interactions and blockers (like copper/zinc balance or iron absorption)

• What you should ask your doctor or practitioner to test, and how to use this data to guide treatment or referrals

Why Blood Tests Are Important in Hair Loss

Hair follicles are highly metabolically active, with a rapid cell turnover similar to the gut and skin. This means they are sensitive to changes in nutrient status, hormones, inflammation, and stress.

Many types of hair loss have overlapping symptoms, like shedding, thinning, or reduced density, but the underlying causes can vary drastically. Blood testing helps clarify which systems are under stress so treatment can be personalised.

Categories of Hair Loss & Their Relevant Blood Tests

1. Genetic or Hormonal Hair Loss (Androgenetic Alopecia)

This is the most common type of hair loss, driven by genetics and androgens such as DHT (dihydrotestosterone). While genetics set the stage, other factors, including metabolic health, can influence the speed and severity of progression.

Key tests:

• Total Testosterone

• Free Testosterone

• SHBG (Sex Hormone Binding Globulin)

• Free Androgen Index (calculated: Total Testosterone ÷ SHBG × 100)

• DHEA-S (especially in women under 40)

• Zinc & Copper (supportive in hormone metabolism and inflammatory balance)

• Lipid panel (total cholesterol, LDL, HDL, triglycerides, non-HDL cholesterol)

• Fasting glucose / HbA1c (screens for early insulin changes)

Why metabolic tests matter:
Insulin resistance and abnormal lipid profiles are more common in early-onset AGA. High insulin can lower SHBG, leaving more free testosterone to be converted into DHT at the follicle. Dyslipidemia (low HDL, high triglycerides, high LDL) is often linked to low-grade inflammation, which may contribute to follicle miniaturisation.

Optimal ranges for hair health:

• SHBG: 60–100 nmol/L (higher helps reduce free androgen load)

• Free Androgen Index: <2.5 for women

• HDL: upper half of lab range

• Triglycerides: lower half of range

• Zinc: upper half of reference range (aim >14 µmol/L)

• Copper: balanced with zinc (Zinc:Copper ratio ~8:1)

 2. Stress-Induced Hair Loss (Telogen Effluvium / Chronic Shedding)

This often follows emotional, physical, or physiological stress (surgery, illness, postpartum, emotional trauma).

Test for:

• Ferritin (iron stores)

• Serum Iron

• Transferrin Saturation

• CRP / ESR (inflammation markers)

• TSH, Free T3, Free T4 (thyroid function)

• Vitamin B12

• Vitamin D (25-OH)

• Zinc

• Magnesium (RBC magnesium ideal)

Optimal Levels:

• Ferritin:

          ~ Women with hair loss: ≥70–100 µg/L

          ~ Below 30 = insufficient for follicle activity

• Vitamin D: ≥100–125 nmol/L

• Vitamin B12: >400 pmol/L

• Thyroid (TSH): 1.0–2.0 mU/L

• Free T3/T4: upper half of reference range

 3. Nutritional Deficiency Hair Loss

This is common in restrictive diets, post-bariatric surgery, digestive disorders, or poor nutrient absorption.

Test for:

• Ferritin + Full Iron Panel

• Vitamin B12 & Active B12 (HoloTC)

• Folate

• Vitamin D

• Zinc & Copper

• Magnesium

• Vitamin A (Retinol)

• Protein / Albumin

• Homocysteine (can signal B vitamin need even if serum levels appear normal)

• Methylmalonic Acid (MMA) (for B12 deficiency detection)

Tip:
Even when nutrients are within range, they may not be high enough for optimal hair support. For example, someone with ferritin at 35 µg/L is technically “normal,” but it’s too low to support robust hair growth.

4. Autoimmune & Inflammatory Hair Loss (e.g. Alopecia Areata)

Hair loss from autoimmune causes often shows sudden patchy shedding, nail pitting, or eyebrow loss.

Test for:

• ANA (Antinuclear Antibodies)

• Thyroid antibodies (TPO, TgAb)

• CRP / ESR

• Vitamin D (critical for immune modulation)

• Zinc (immune system regulation)

• Ferritin

• Coeliac screen (TTG-IgA + Total IgA)

• Iron panel

When “Normal” Isn’t Good Enough – The Absorption Puzzle

A client may have normal serum iron, but if ferritin is low, this means iron isn’t being adequately stored or utilised.

Common blockers of nutrient absorption:

• Low stomach acid (hypochlorhydria) → affects iron, B12, zinc

• Excess calcium → inhibits iron and magnesium absorption

• High copper → antagonises zinc absorption

• Phytates (in whole grains, legumes) → bind minerals and reduce uptake

• Chronic inflammation → traps iron inside cells (functional iron deficiency)

Tip: If ferritin won’t budge despite supplementation, consider checking:

• Gut health
• Coeliac screen
• Copper, zinc ratio
• Inflammatory markers (CRP, ESR)

How to Prepare for Blood Tests

• Iron: Test in the morning, fasted, and avoid iron supplements for 24 hours before

• Zinc & Copper: Avoid multivitamins for at least 3–5 days

• B12 & Folate: Fasted if possible

• Thyroid: If medicated, test before taking thyroid medication that day

Blood Test Checklist for Hair Loss

Understanding blood work from a hair point of view requires a shift in thinking. Just because your levels are within the lab’s "normal" range doesn’t mean they're optimal for growing healthy, resilient hair.

As a trichologist, I use blood testing as one piece of the puzzle, alongside scalp analysis, hair cycle assessment, lifestyle, and nutritional habits, to guide a personalised plan that helps restore balance and encourage regrowth.

This content in this article is provided for informational and educational purposes only and is not intended as medical advice. It is designed to help guide conversations with your GP or qualified healthcare professional regarding appropriate blood testing and health investigations. Any medical testing or treatment decisions should be made in consultation with your healthcare provider.

If you’re struggling with hair loss and want support interpreting your blood results from a hair-focused perspective, I offer online consultations and custom trichology programs. Get in touch here