Recommended Laboratory Tests for Hair Loss Evaluation
For evaluating hair loss, laboratory testing should include complete blood count, iron studies (ferritin, serum iron, TIBC), thyroid function tests (TSH, free T4), vitamin D level, and screening for autoimmune disorders when clinically indicated. 1
Diagnostic Approach to Hair Loss
Hair loss evaluation requires a systematic approach that combines clinical assessment with targeted laboratory testing. The British Journal of Dermatology and American Academy of Dermatology recommend a comprehensive diagnostic strategy based on the pattern and characteristics of hair loss.
Initial Clinical Assessment
Before ordering laboratory tests, consider:
- Pattern of hair loss (diffuse vs. localized, scarring vs. non-scarring)
- Onset and progression (acute vs. chronic)
- Associated symptoms (scalp inflammation, itching)
- Medical history (recent illness, medications, nutritional status)
- Family history of hair disorders
Recommended Laboratory Tests
Based on the most recent guidelines, the following tests are recommended:
Basic Screening Tests:
- Complete blood count (CBC)
- Comprehensive metabolic panel
- Thyroid function tests (TSH, free T4)
- Ferritin and iron studies (serum iron, TIBC, transferrin saturation)
- 25-hydroxyvitamin D level
Additional Tests Based on Clinical Suspicion:
For suspected autoimmune etiology:
- Antinuclear antibody (ANA)
- Erythrocyte sedimentation rate (ESR)
- C-reactive protein (CRP)
For suspected hormonal imbalance:
- Total and free testosterone
- Dehydroepiandrosterone sulfate (DHEAS)
- Sex hormone-binding globulin (SHBG)
- Luteinizing hormone (LH) and follicle-stimulating hormone (FSH)
For suspected nutritional deficiencies:
- Zinc level
- Vitamin B12 and folate levels
- Protein status assessment
Specific Testing for Common Hair Loss Conditions
Telogen Effluvium
Telogen effluvium is often triggered by specific factors that can be identified through laboratory testing:
- Iron deficiency is the most common nutritional deficiency associated with chronic diffuse telogen hair loss 1
- Thyroid disorders can trigger telogen effluvium and should be evaluated with TSH and free T4 1
- Nutritional deficiencies, particularly iron, vitamin D, and zinc, should be assessed 1
Androgenetic Alopecia
While primarily diagnosed clinically, hormonal evaluation may be helpful in some cases:
- Hormonal testing is particularly important for women with signs of hyperandrogenism
- Consider testing total and free testosterone, DHEAS, and SHBG
Alopecia Areata
As an autoimmune condition, consider:
- Thyroid function tests (associated with autoimmune thyroid disease)
- Screening for other autoimmune conditions if clinically indicated
Common Pitfalls in Laboratory Testing
- Overreliance on laboratory tests: Many cases of hair loss can be diagnosed clinically without extensive testing 2
- Misinterpretation of ferritin levels: While low ferritin is associated with hair loss, optimal levels for hair health may be higher than the laboratory reference range
- Failure to consider medication-induced hair loss: Review all medications before extensive laboratory workup
- Inadequate follow-up testing: Some conditions require monitoring of laboratory values during treatment
Clinical Pearls
- Iron deficiency is a key factor in chronic diffuse telogen hair loss, with iron serving as a cofactor for DNA synthesis in hair follicle matrix cells 1
- Vitamin D deficiency is associated with lower serum 25(OH)D levels in alopecia patients and affects normal hair follicle function 1
- Laboratory testing is often unnecessary for common causes of hair loss but can help identify systemic causes that might otherwise be overlooked 3
- A methodical approach to evaluating hair loss can lead to appropriate treatment and significant patient satisfaction 3
Remember that while laboratory tests are valuable tools, they should be ordered selectively based on clinical presentation rather than as a standard panel for all patients with hair loss.