Which blood test can detect perimenopause?

Perimenopause sets in gradually, usually between the ages of 35 and 45, and each woman experiences it differently. It is a period of natural adjustment that happens gradually: the body changes its hormonal functioning, sometimes without any obvious signs at first.

Why get a blood test for perimenopause?

Perimenopause is often accompanied by vague symptoms: unusual fatigue, irregular cycles, and mood swings. When faced with these signs, the question of having a blood test often arises. Can it really help identify perimenopause? And above all, how can the results be interpreted accurately?

The objective is not to provide a formal diagnosis, but to offer guidance.

A biological assessment can help to determine:

• to observe certain hormonal trends (fluctuations in estrogen, a relative decrease in progesterone, and a progressive increase in FSH),
• to compare this data with feelings,
• and to rule out other potential causes, such as thyroid or metabolic conditions, when symptoms persist.

It is important to remember that blood test results reflect a specific moment in time. During perimenopause, hormonal fluctuations tend to be more pronounced and unpredictable, meaning that a single test cannot provide a full picture of hormonal function. It is part of an observation process, not a definitive confirmation

Which hormone tests should be performed?

Several tests are generally mentioned when discussing perimenopause.

The main ones concern ovarian hormones:

• Estradiol (E2), whose concentrations may be low, normal, or sometimes high, with irregularity being more informative than the isolated value.
• Progesterone levels are often lower due to more frequent anovulatory cycles and are implicated in numerous functional symptoms.
• FSH (follicle-stimulating hormone) tends to increase during hormonal transitions, sometimes remaining within normal ranges.
• LH (luteinizing hormone), less specific, but useful as a supplement.

In some women, particularly those under the age of 45, an AMH (anti-Müllerian hormone) test may be recommended to assess ovarian reserve. This marker alone cannot identify perimenopause, but it can provide additional context. 

At the same time, it is important to assess thyroid function, since thyroid imbalances can mimic or exacerbate the symptoms of perimenopause. Tests usually include: TSH, fT4, and fT3. If an autoimmune disease is suspected, additional testing for antithyroid antibodies may be required.

Depending on individual circumstances, an evaluation of cortisol and DHEA-S may also be relevant, as chronic stress and adrenal function play a significant modulating role in symptoms.

Finally, certain tests, known as field tests, can contribute to a more comprehensive assessment without constituting a diagnosis. These tests include ferritin, vitamin D, vitamin B12, glycemic, and lipid parameters. These blood tests are only performed in cases of natural cycles or when mechanical contraception, such as condoms or copper IUDs, is used. However, no hormone tests (oestrogen, progesterone, etc.) are performed on women using hormonal contraception, such as the pill, implants, or IUDs.

When should the blood test be performed?

The timing of the cycle is a determining factor in interpreting the results. FSH, LH, and estradiol levels are generally more comparable when measured at the beginning of the cycle, typically between days 3 and 5. Progesterone, on the other hand, is measured during the luteal phase, ideally around 7 days after the ovulation peak.

When cycles are still identifiable, ovulation occurs between 11 and 16 days before the onset of menstruation. It is therefore no longer relevant to rely on the old idea that ovulation always occurs on day 14, with a routine blood test on day 21.

This approach does not reflect the physiological reality for many women. During perimenopause, this synchronization can become more complex, as cycles tend to vary from month to month. A blood test taken at a given moment provides a snapshot, but not a dynamic view of hormonal functioning.

This is why it is sometimes necessary to repeat tests over time to identify a trend, rather than interpreting a single value. This temporal dimension highlights that perimenopause is a long-term process: hormonal variations are better understood when observed over several months than from a single sample.

How should the results be interpreted?

The results must be interpreted with great caution. Values within the usual ranges do not rule out the onset of perimenopause, while certain isolated variations do not necessarily indicate a lasting change in the hormonal axis.

Biological data becomes truly meaningful when combined with clinical experience: cycle changes, sleep quality, energy levels, mood, and sensitivity to stress. This perspective allows us to understand what the body is expressing, without jumping to conclusions based on isolated figures.

It is also important to avoid interpreting the results in an anxiety-provoking way. Hormones fluctuate in waves, and perimenopause is not a fixed state but a dynamic process. The tests are indicators, not verdicts.

Are there other ways to confirm perimenopause?

Yes. While biological analyses are important, observing daily life remains central: this includes gradual changes in menstrual cycles, changes in cervical mucus, sleep disturbances, and variations in energy, concentration, or stress tolerance.

Perimenopause is characterised by a combination of consistent symptoms rather than a single test result. This comprehensive approach recognises the physiological complexity of this transitional phase and avoids overinterpreting a single parameter.