Which Blood Tests Are Required for Hair Loss in Women?

Key Takeaways: 

• What are the most common blood tests used to investigate hair loss? The most common blood panel required in generalised hair loss in women will be a full blood count (FBC), a check of your body’s iron stores (ferritin) and a thyroid gland function screen.
  
• Why a blood test? Blood tests can help detect causes of hair loss that are not at first apparent from a history and scalp examination.
  
• Will it find a cause? Blood testing will not always find a cause, especially if you have pattern or structural hair loss. It is used as an adjunct to help in diagnosing.
  
• What is the most common abnormality seen? The most common finding in women with hair loss is reduced iron store levels.
  
• Is there anything I should do before my blood test? Tell your doctor about any supplements or medications you are currently taking before your blood is taken.
  

Blood testing can help narrow down the possible causes of hair loss in women. They are useful because the appearance of hair loss alone does not always reveal if there is an underlying source that must be taken into account.

Which Blood Tests Are Used for Hair Loss in Women? 

There is no single set of blood test required for every woman with hair loss, 

ratherAny testing you undergo should be guided by the pattern of hair loss, your medical history, and a scalp examination.

If you have typical female-pattern hair loss, you may not require any blood testing.

A common set of blood tests doctors may run if you have diffuse hair loss all over the scalp, rather than concentrated in one area, may include testing for a full blood count (FBC), Iron store level (ferritin), and thyroid hormone level testing.¹

Some characteristic patterns of hair loss will prompt a check of related autoimmune conditions such as thyroid disease.²

The doctor may look at other markers such as vitamin D, B12, folate, zinc and certain hormones if they suspect an underlying cause.³

Blood tests help identify underlying causes of your hair loss, they cannot, when taken on their own, diagnose most hair loss conditions. 

Understanding Each Test and its Interpretation

The relevance of different blood test markers to your hair loss are listed below:

• Ferritin & iron studies-  Estimate the stored iron in the body. Low stores of iron in the body have been associated with generalised hair loss over all of the scalp.^4,5
  
• Full blood count — Helps to identify anaemia, which can be a trigger for hair loss.
  
• Thyroid (TSH, free T4)– Both underactive and overactive thyroid disease can lead to widespread hair loss, or it can be linked with an autoimmune type of hair loss called alopecia areata. 
  
• Vitamin D– Low levels of vitamin d are associated with some forms of hair loss.^4,6
  
• Vitamin B12 & folate– These nutrients are needed for normal cell division, which is important in hair growth. 
  
• Zinc- Zinc supports normal cell division and follicle function. Most studies show a low level of zinc in people with autoimmune type hair loss.³

When Do I Need to Do Hormonal Testing

Hormone tests are not routinely needed for typical female pattern hair loss. They may be used to identify certain endocrine disorders if they are considered to be a underlying cause for hair loss.

They may be added when you have hair loss with: 

• Irregular or absent periods,

• Increased facial or bodily hair

• Severe acne

• Rapidly progressive hair thinning

• Other signs consistent with too high levels of potent androgens, such as dihydrotestosterone in your body, which is linked with hair loss in women.⁷

In this case, the tests sent off may include checks for the following hormone parameters:

Total testosterone, free androgens, dehydroepiandrosterone sulfate (DHEAS), and androstenedione. 

Further laboratory testing, e.g., 17-OH-progesterone, follicle-stimulating hormone, oestradiol, prolactin, or cortisol, may also be necessary.¹

When to Do a  Blood Test?

Extensive blood work is not necessary in all cases. In fact, they help only when your doctor suspects a link between a certain deficiency or excess and your hair loss. 

Blood tests are most useful when hair loss is spread out evenly all over your scalp, and there are specific other signs of conditions such as 

• Iron deficiency or anaemia
  
• Thyroid disease
  
• Nutritional deficiency
  
• Hormonal imbalances

Blood tests are not helpful in providing a diagnosis of your hair loss without a proper medical history and assessment by a doctor.

How to Prepare for Hair Loss Blood Tests

You can prepare for your blood test by: 

• Ensuring that you disclose all medicines and supplements you are taking when asked by your doctor. Certain supplements such as Vitamin B7 (biotin) are especially notable as they can specifically alter blood testing of some hormonal and vitamin tests, especially thyroid tests. It is recommended to stop taking any biotin-containing supplements up to 48 hours before your blood test to allow it to leave your system to obtain a more accurate blood test result.⁸

• Ensuring you follow any fasting instructions given to you before the test.

• Not stopping any prescribed medications or hormonal contraception without specifically being directed to do so.

• Attending for the blood test at the right time. You may be guided on when a blood test is best taken to produce accurate results, especially as some hormones fluctuate with your menstrual cycle and other factors such as the time of day, i.e morning versus afternoon.

What Happens After Your Results

If your blood test results return as normal, the hair loss is likely pattern- or structure-based. You may need to follow up with a more detailed scalp examination or be referred to a dermatology specialist for a more accurate diagnosis.

If the results of the blood test come back as outside the normal range, treatment will likely be directed at treating the underlying condition. Once this is corrected, your hair should resume growing as normal, provided this deficiency was the cause.

Interpretation and guidance of any results should be carried out by your doctor or a licensed healthcare professional. 

Conclusion

A full blood count(FBC), ferritin and thyroid testing are the most common tests used initially to investigate widespread hair loss and thinning. Further testing should be added only when your doctor considers that these specific additional tests will provide a clearer picture of the cause of your hair loss.

No single blood test would diagnose your hair loss. Blood test results must be interpreted as a whole, taking into account the pattern of your hair loss and a scalp examination, and pieced together by your treating doctor.

References:

1. Blume-Peytavi U, Blumeyer A, Tosti A, Finner A, Marmol V, Trakatelli M, et al. S1 guideline for diagnostic evaluation in androgenetic alopecia in men, women and adolescents. Br J Dermatol. 2011;164(1):5-15. doi:10.1111/j.1365-2133.2010.10011.x. 
2. Lee S, Lee YB, Kim BJ, Lee WS. Screening of thyroid function and autoantibodies in patients with alopecia areata: a systematic review and meta-analysis. J Am Acad Dermatol. 2019;80(5):1410-1413.e4. doi:10.1016/j.jaad.2018.10.066. 
3. Almohanna HM, Ahmed AA, Tsatalis JP, Tosti A. The role of vitamins and minerals in hair loss: a review. Dermatol Ther (Heidelb). 2019;9(1):51-70. doi:10.1007/s13555-018-0278-6. 
4. Ahmed A, Alali A, Alahmadi M, Alghamdi S, Khawaji Z, Humedi A, et al. Association between serum trace elements and telogen effluvium: a systematic review and meta-analysis. Skin Appendage Disord. 2026 Mar 18 [online ahead of print]. doi:10.1159/000550921. 
5. Treister-Goltzman Y, Yarza S, Peleg R. Iron deficiency and nonscarring alopecia in women: systematic review and meta-analysis. Skin Appendage Disord. 2022;8(2):83-92. doi:10.1159/000519952. 
6. Yongpisarn T, Tejapira K, Thadanipon K, Suchonwanit P. Vitamin D deficiency in non-scarring and scarring alopecias: a systematic review and meta-analysis. Front Nutr. 2024;11:1479337. doi:10.3389/fnut.2024.1479337. 
7. Elhassan YS, Hawley JM, Cussen L, Abbara A, Clarke SA, Kempegowda P, et al. Society for Endocrinology clinical practice guideline for the evaluation of androgen excess in women. Clin Endocrinol (Oxf). 2025;103(4):540-566. doi:10.1111/cen.15265. 
8. Gifford JL, Sadrzadeh SMH, Naugler C. Biotin interference: underrecognized patient safety risk in laboratory testing. Can Fam Physician. 2018;64(5):370. PMID: 29760259; PMCID: PMC5951654.