Thyroid, iron and hormones: which tests to ask for

In the years around the menopause, tiredness, hair loss, and changes in weight and mood are common. They are often attributed to hormones. But there are two common, treatable causes that are easily mistaken for the menopause: thyroid problems and iron deficiency. And there are hormone tests that many women ask for and that, in most cases, are not necessary.

In this guide we explain the reason for each one, which other tests are useful at this stage and how to prepare. For the general guide, see Blood tests for hair loss: what to ask for.

In summary:

• TSH (thyroid): useful, because hypothyroidism is more common after the menopause and the symptoms overlap;
• full blood count and ferritin: useful, especially if there are or were heavy periods in the perimenopause;
• FSH and oestradiol: in women over 45 with typical symptoms, they are not needed to diagnose the menopause;
• male hormones: only when there are signs of excess.

Thyroid: the great imitator of the menopause

Why it is worth asking for

Thyroid diseases are much more common in women and increase with age. In a study of more than 53,000 women aged 40 or over, hypothyroidism was about 60% more common in late perimenopause and after the menopause than before, and subclinical hypothyroidism about 20% more common (Kim et al., 2022).

Overlapping symptoms

Because of this overlap, a thyroid problem can be attributed to the menopause for months.

What is requested

• TSH: the screening test. If it is normal, the thyroid is usually fine.
• Free T4: if TSH is abnormal, to confirm and understand the severity.
• Anti-thyroid antibodies (anti-TPO): if there is hypothyroidism or borderline TSH, to find out whether there is an autoimmune (Hashimoto's) thyroiditis.

Thyroid and hair

Both hypothyroidism and hyperthyroidism can cause diffuse hair loss. When thyroid function is corrected, hair loss usually slows, but hair recovers at its own pace, over months. Autoimmune thyroid diseases are also more common in people with alopecia areata.

Iron: the perimenopause can deplete reserves

Heavy periods before the menopause

In the years leading up to the menopause, cycles become irregular and many women have heavier or longer periods. In a study published in 2025 in the journal Menopause, of about 2,300 middle-aged women, about one in three had abnormal bleeding in the perimenopause, and heavy or prolonged periods were strongly associated with tiredness.

These losses can deplete iron reserves, and low ferritin is associated with hair loss in women, even without anaemia, with a greater difference before the menopause (Treister-Goltzman et al., 2022).

What is requested

• Full blood count: shows whether there is anaemia.
• Ferritin: shows reserves. It can be low with normal haemoglobin.
• CRP: requested together, because inflammation raises ferritin and can hide iron deficiency.

In hair loss, a ferritin below 30 to 40 ng/mL may already reflect insufficient reserves, even if the laboratory considers it normal.

After the menopause

When periods stop, iron needs fall to values similar to men's, about 11 mg a day. Iron deficiency after the menopause is less common and, when it appears, should always be investigated: it may indicate blood loss from the gut, absorption problems or an insufficient diet.

Vaginal bleeding after the menopause (more than 12 months without a period) is not normal and should be assessed by your GP or gynaecologist without delay.

Find out more about iron in your diet in Protein, iron and zinc: what your hair needs.

Hormones: when they are useful and when they are not

Diagnosing the menopause does not require blood tests (after 45)

Many women ask for hormone tests to "confirm" the menopause. The guidance from NICE, the UK reference, is clear (NICE, NG23):

• in women over 45 with symptoms, the perimenopause is diagnosed by hot flushes and irregular cycles, and the menopause by 12 months without a period, without hormonal contraception;
• in these women, do not use anti-Müllerian hormone, inhibin, oestradiol, follicle count or ovarian volume to make the diagnosis;
• FSH is only considered between 40 and 45 with symptoms, or before 40 when early menopause is suspected, in which case two tests 4 to 6 weeks apart are needed;
• FSH is not suitable for diagnosing the menopause in those taking the combined pill or a high-dose progestogen.

Why? In the perimenopause hormones vary a great deal from month to month and even from day to day. A single test may be normal one day and abnormal the next, and does not change the clinical decision.

Male hormones: only if there are signs of excess

In menopausal hair loss, most women have normal male hormones. Tests (total testosterone, SHBG, DHEA-S and, sometimes, prolactin) are requested when there is:

• coarse hairs appearing on the face, chest or abdomen;
• persistent acne;
• hair loss that progresses quickly;
• signs of virilisation: deeper voice, increased muscle mass, enlarged clitoris.

A rapid rise in male hormones after the menopause is rare but requires prompt assessment, to rule out tumours of the ovary or adrenal glands.

What if I am already on hormone therapy?

Sex hormone tests are generally not needed to adjust hormone therapy: the dose is adjusted by symptoms. Oral oestrogen therapy can alter some test results, such as SHBG and the proteins that carry thyroid hormone, and the doctor takes this into account.

Other useful blood tests at this stage of life

They are not specific to hair, but the menopause is a good time to take stock, because cardiovascular and metabolic risk increases.

• Vitamin D: deficiency is common and matters for bone health, which becomes more fragile after the menopause.
• Vitamin B12: especially in vegetarians, and in those who take metformin or stomach medicines for a long time.
• Fasting blood glucose or glycated haemoglobin: the risk of diabetes increases after the menopause.
• Lipid profile (cholesterol and triglycerides): values tend to rise after the menopause.
• Kidney and liver function: before some oral treatments.

Your GP can combine these tests in a single request, together with those that make sense for hair loss.

Summary: which tests for each situation

This table is a general guide. The tests should be chosen by the doctor, after the consultation.

How to prepare and pitfalls to avoid

• Biotin: many "hair, skin and nails" supplements contain biotin, which can distort TSH and T4 results, mimicking hyperthyroidism. Stop taking it at least 1 day beforehand, or longer if the dose is high, and tell your doctor (Fan et al., 2019).
• Levothyroxine: if you take thyroid medication, follow your doctor's advice on whether to take it before or after the blood sample, and always keep the same timing between tests.
• Iron supplements: if you are taking iron, ask whether you should take a break before the blood test.
• Hormone therapy or contraception: always tell your doctor, because they alter some test results.
• Time: in the morning, especially for hormones. If you still have periods and the doctor has requested hormone tests, sample between day 2 and day 5 of the cycle.
• Fasting: needed for blood glucose and, sometimes, for the lipid profile; check with the laboratory.
• Recent illness: a recent infection raises ferritin and CRP; it may be better to postpone.
• Bring previous test results for comparison: the trend over time says a lot.

When to seek a medical assessment

The first three signs justify an assessment without delay; the rest, a routine appointment.

At Luxmed, the Hair Medicine consultation assesses the type of hair loss with trichoscopy and requests, when indicated, the tests that make sense in your case. If you already have recent test results, bring them.

This article is for information only and does not replace a medical consultation.

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