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What tests are needed for hair loss?

Content owner/Author: Specialist Dr. Utkan Kızıltaç — Dermatology Specialist

Last medical review and update: September 10, 2026

Not everyone experiencing hair loss needs the same blood tests. Laboratory investigations should be planned according to the type and duration of hair loss, age, gender, accompanying symptoms, nutritional history, and dermatological examination findings.

First, the type of hair loss should be determined, and then the truly necessary tests should be ordered.

What tests can be considered in telogen effluvium?

In diffuse hair loss where no clear trigger is found, complete blood counts, ferritin levels, and, if necessary, iron and thyroid function tests are frequently evaluated. Based on clinical history, B12, folate, vitamin D, or zinc supplementation may be considered; however, there is no strong evidence to routinely recommend all of these for everyone.

Why is ferritin important?

Iron deficiency can be accompanied by diffuse hair loss. However, there is no single universally accepted "ferritin threshold for hair loss." Ferritin should be interpreted in conjunction with hemoglobin, other iron parameters, menstruation, diet, and inflammation.

Are thyroid tests necessary?

If there are symptoms such as unexplained generalized hair loss or fatigue, weight changes, hot/cold intolerance, palpitations, constipation, or menstrual irregularities, TSH and, if necessary, free T4 levels may be assessed.

Should everyone be tested for vitamin D, B12, folate, zinc, and biotin?

No. These tests should be targeted based on clinical risk and history. Biotin deficiency is rare, and high doses of biotin may interfere with some laboratory tests.

When are hormone tests necessary?

Total testosterone and other androgen tests, depending on the clinical situation, may be considered, especially in women, if there is new or noticeable increase in hair growth, irregular periods, severe acne in adulthood, rapidly progressing hair thinning, infertility, or signs of virilization.

Is a hormone test necessary for male pattern hair loss?

In typical androgenetic alopecia, this is usually not necessary. Normal testosterone does not rule out androgenetic alopecia; the disease is related to the genetic androgen sensitivity of the follicle.

What tests are needed for alopecia areata?

Diagnosis is usually made through clinical examination and trichoscopy. Targeted tests may be performed if there are symptoms suggestive of thyroid or other autoimmune diseases, or a family history. Hair loss alone is not sufficient grounds for a comprehensive autoimmune panel.

If the test results are normal, does that mean there is no hair loss?

No. Blood tests may be normal in many cases of androgenetic alopecia and telogen effluvium. Trichoscopy provides more direct information than laboratory tests in most patients.

Instead of ordering a comprehensive laboratory panel for hair loss, it is necessary to base the diagnosis on the hair loss pattern, trichoscopy, history, and accompanying findings. Tests are not a substitute for diagnosis; they should be used targetedly to confirm clinical suspicion or investigate underlying causes.

Dermatologist's Perspective

Scientific Resources

1. Öner Ü, Akdeniz N. Telogen effluvium in daily practice: Patient characteristics, laboratory parameters, and treatment modalities of 3028 patients with telogen effluvium. J Cosmet Dermatol. 2022;21:2610-2617. PMID: 34449961. DOI: 10.1111/jocd.14413. https://pubmed.ncbi.nlm.nih.gov/34449961/

2. Miller RC, Abedian S, Lipner SR. “Shedding” low yield testing for telogen effluvium: A cross-sectional study of 16,381 laboratory results. J Am Acad Dermatol. 2023;89(3):623-626. PMID: 37245837. DOI: 10.1016/j.jaad.2023.05.045. https://pubmed.ncbi.nlm.nih.gov/37245837/

3. Karakoyun Ö, Ayhan E, Yıldız İ. Retrospective Review of 2851 Female Patients With Telogen Effluvium. J Cosmet Dermatol. 2025;24(2):e70037. PMID: 39950230. DOI: 10.1111/jocd.70037. https://pubmed.ncbi.nlm.nih.gov/39950230/

4. Association between Serum Trace Elements and Telogen Effluvium: A Systematic Review and Meta-Analysis. 2026. PMID: 42077991. https://pubmed.ncbi.nlm.nih.gov/42077991/

5. Daunton A, Harries M, Sinclair R, Paus R, Tosti A, Messenger A. Chronic Telogen Effluvium: Is it a Distinct Condition? A Systematic Review. Am J Clin Dermatol. 2023;24(4):513-520. PMID: 37052778. DOI: 10.1007/s40257-023-00760-0. https://pubmed.ncbi.nlm.nih.gov/37052778/

6. A comprehensive investigation of biochemical status in patients with telogen effluvium. 2024. PMID: 39107936. https://pubmed.ncbi.nlm.nih.gov/39107936/

7. Cheng T, Fang H, Wang Y, et al. The Diagnostic Value of Serum Ferritin for Telogen Effluvium. Clin Cosmet Investig Dermatol. 2021. PMID: 33603430. DOI: 10.2147/CCID.S291170. https://pubmed.ncbi.nlm.nih.gov/33603430/

8. Nonscarring scalp alopecia: Which laboratory analysis should we perform on whom? 2021. PMID: 34688244. https://pubmed.ncbi.nlm.nih.gov/34688244/

9. Carmina E, Azziz R, Bergfeld W, et al. Female Pattern Hair Loss and Androgen Excess. J Clin Endocrinol Metab. 2019;104(7):2875-2891. PMID: 30785992. DOI: 10.1210/jc.2018-02548. https://pubmed.ncbi.nlm.nih.gov/30785992/

10. Society for Endocrinology Clinical Practice Guideline for the Evaluation of Androgen Excess in Women. 2025. PMID: 40364581. https://pubmed.ncbi.nlm.nih.gov/40364581/

11. Manabe M, Tsuboi R, Itami S, et al. Guidelines for the diagnosis and treatment of male-pattern and female-pattern hair loss, 2017 version. J Dermatol. 2018;45(9):1031-1043. PMID: 29863806. DOI: 10.1111/1346-8138.14470. https://pubmed.ncbi.nlm.nih.gov/29863806/

12. Shrivastava SB. Diffuse hair loss in an adult female: approach to diagnosis and management. Indian J Dermatol Venereol Leprol. 2009;75:20-31. PMID: 19172026. DOI: 10.4103/0378-6323.45215. https://pubmed.ncbi.nlm.nih.gov/19172026/

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