Hair loss in women even though blood tests are normal: ferritin, thyroid, hormones

After washing your hair, there is more hair in the drain than there used to be, whole clumps collect in your brush, and your ponytail feels thinner. You went to the doctor, had blood taken – and the answer was: “Your blood tests are normal.” But then why is your hair falling out?

Hair loss in women is common and very distressing for many. This article explains which forms there are, why hair often only falls out months after the trigger, which values are often discussed in hair loss – and why “normal blood tests” does not always mean that all the important values were measured.

Why hair often only falls out months later

Every hair goes through a cycle. Most of the hair on your head is in the growth phase, which lasts several years. A smaller proportion is resting. After a resting phase of a few months, the old hair falls out and a new one grows (PubMed 28613598).

If the body goes through a major strain, many hairs can suddenly switch to the resting phase at the same time. But they only fall out a few months later. Experts call this telogen effluvium. Typical triggers are an illness with fever, surgery, the time after giving birth, stopping hormonal contraception, a crash diet, too little protein, an underactive thyroid, iron deficiency or certain medications (PubMed 28613598). That is why it is worth thinking back about three months when looking for the cause.

This form is usually temporary: once the trigger is over, the hair grows back.

Hereditary hair loss in women

A second common form is hereditary hair loss. In women, the hair gradually thins mainly at the parting and on the top of the head, while the hairline at the forehead is usually preserved. The hair follicles become smaller and produce thinner hair (PubMed 30627618). This form increases with age, especially after the menopause.

If there are also signs of an excess of male hormones – such as irregular periods, acne or increased facial hair growth – this should be checked by a gynaecologist or dermatologist (PubMed 30627618). The earlier the diagnosis, the better progression can be halted.

Hair loss, but normal blood tests: what was often not measured

As with tiredness, the same applies here: “normal blood tests” only refers to the values that were actually measured. These values are often discussed in hair loss:

• Ferritin: It shows your iron stores. Iron deficiency is one of the known triggers of diffuse hair loss (PubMed 28613598). Whether a ferritin level in the lower normal range already plays a role is debated; the evidence is not consistent (PubMed 16635664). Ferritin should always be considered together with an inflammation marker (PubMed 16635664).
• Thyroid (TSH): An underactive thyroid is one of the known triggers of hair loss (PubMed 28613598).
• Vitamin D, zinc, folic acid, vitamin B12: They are involved in the hair cycle. However, there is little good evidence for a benefit of supplements without a proven deficiency (PubMed 30547302).
• Hormones: in case of cycle disorders or signs of an excess of male hormones (PubMed 30627618).

Important: too much can also be harmful. An excess of vitamin A or selenium has itself been described as a cause of hair loss (PubMed 30547302) (PubMed 28613598). High-dose supplements taken on the off chance are therefore not a good idea.

Biotin before a blood test: an underestimated pitfall

Many hair supplements contain high-dose biotin. In one study, taking 10 mg of biotin a day – an amount common in supplements – changed the results of several lab tests, including thyroid values. This can make values appear falsely high or falsely low (PubMed 28973622). So let them know before every blood test if you are taking biotin, and check with your doctor whether you should pause it beforehand.

When you should see a dermatologist

• round bald patches
• very sudden, heavy hair loss
• redness, scaling, itching or pain of the scalp
• hair loss that lasts longer than six months or clearly increases
• signs of a hormonal imbalance such as irregular periods, acne or beard growth

If you take medication that could be linked to hair loss, mention it. Do not stop a prescribed medication without talking to your doctor first.

Measuring values yourself: what is possible with ORY

With a small blood sample from your fingertip, which you take at home, some of the values mentioned can be measured:

• The OM Vital blood test measures ferritin, TSH, hs-CRP, vitamin B12, vitamin D, folic acid and selenium, among others.
• The whole blood mineral analysis determines minerals such as zinc, magnesium and selenium in whole blood.
• The Female hormone profile measures oestradiol, progesterone, testosterone, DHEA and cortisol in saliva.

The results are building blocks, not a diagnosis. Feel free to take them to your dermatologist, gynaecologist or GP. The ORY expert team can also support you in interpreting them. If you are also tired all the time, read our article Always tired even though your blood tests are normal?

In brief

• Hair often only falls out two to three months after the trigger.
• Common forms are temporary telogen effluvium and hereditary hair loss.
• Ferritin, thyroid and, depending on the situation, hormones are often discussed in hair loss – they are often not included in routine blood tests.
• Too much vitamin A or selenium can itself cause hair loss; biotin can distort lab values.
• Bald patches, scalp complaints or heavy, persistent hair loss should be checked by a dermatologist.

Frequently asked questions

Hair loss in women with normal blood tests – what could be the cause?

Often ferritin, thyroid values or hormones were not measured. In addition, a trigger such as an illness, giving birth or severe stress may have been months ago (PubMed 28613598). Hereditary hair loss also does not show up in the blood (PubMed 30627618).

What blood tests should I get for hair loss?

Commonly discussed are a blood count, ferritin together with an inflammation marker, TSH, vitamin D, zinc and, depending on the situation, hormones. Which ones make sense for you depends on your medical history.

Can iron deficiency cause hair loss?

Yes, iron deficiency is one of the known triggers of diffuse hair loss (PubMed 28613598). The ferritin level at which this plays a role has not been clearly established (PubMed 16635664).

How long does hair loss last after stress or illness?

Hair usually falls out two to three months after the trigger. Once the cause is over, it usually grows back; it often takes several more months until this becomes visible (PubMed 28613598).

Does biotin help with hair loss?

A true biotin deficiency is rare, and there is little evidence of a benefit without a deficiency (PubMed 30547302). High-dose biotin can also distort lab values such as thyroid values (PubMed 28973622).

Is hair loss during menopause normal?

Hereditary hair loss often increases with the menopause (PubMed 30627618). Even so, it is worth having your thyroid and iron status checked and discussing the options with a dermatologist.

Sources

1. Hughes EC, Saleh D. Telogen Effluvium. StatPearls. 2024. PubMed 28613598
2. Fabbrocini G et al. Female pattern hair loss: A clinical, pathophysiologic, and therapeutic review. Int J Womens Dermatol. 2018. PubMed 30627618
3. Trost LB et al. The diagnosis and treatment of iron deficiency and its potential relationship to hair loss. J Am Acad Dermatol. 2006. PubMed 16635664
4. Almohanna HM et al. The Role of Vitamins and Minerals in Hair Loss: A Review. Dermatol Ther (Heidelb). 2019. PubMed 30547302
5. Li D et al. Association of Biotin Ingestion With Performance of Hormone and Nonhormone Assays in Healthy Adults. JAMA. 2017. PubMed 28973622