What Is FSH and What Should Your Level Be? High and Low FSH

In brief:

• FSH stimulates egg development; its level changes throughout the menstrual cycle (MedlinePlus).
• As the ovaries release fewer eggs, the body makes more FSH; FSH is high in menopause (MedlinePlus).
• The normal range varies between laboratories; a single value cannot make a diagnosis on its own.
• At 45 and over, an FSH test is usually not needed to identify menopause (NICE).

What does FSH do?

FSH passes from the pituitary gland into the blood and reaches the ovaries. There it stimulates egg development and prepares the egg for ovulation (MedlinePlus). The other pituitary hormone, which triggers ovulation, is LH; together they run the cycle. We briefly explain both in the Menopause Glossary.

Apart from the cycle, the biggest change affecting FSH is the menopause transition. According to MedlinePlus, as the ovaries release fewer eggs, the body makes more hormone to trigger ovulation; high FSH is a normal sign of perimenopause and menopause.

Why is an FSH test done?

According to MedlinePlus, an FSH test may be requested in women:

• To help find the cause when pregnancy has not happened after 12 months of trying
• When periods become irregular or stop
• When a condition affecting the ovaries is suspected
• To find out whether menopause or perimenopause has started

We explain who needs a test for menopause in How Is a Menopause Test Done?. In short: healthy people aged 45 and over with symptoms usually do not need a test; it is considered between 40 and 45 and before 40 (NICE).

What should your FSH level be?

Ranges for women given by MedlinePlus (mIU/mL):

• Before puberty: 0–4.0
• Puberty: 0.3–10.0
• Women who still have periods: 4.7–21.5
• After menopause: 25.8–134.8

These ranges vary slightly from laboratory to laboratory (MedlinePlus). Compare your result with the reference range on your report. In women who have periods, FSH changes with the day of the cycle, so your doctor may ask for the test on a particular day (MedlinePlus).

What do high and low FSH mean?

According to MedlinePlus, high FSH in women may be linked to:

• Menopause or perimenopause (including early or premature menopause)
• Early failure of the ovaries (premature ovarian insufficiency)
• Hormone therapy
• Some pituitary gland tumours
• Chromosome differences such as Turner syndrome

Low FSH may be linked to:

• The pituitary gland or hypothalamus not making enough hormones
• Very low weight or rapid weight loss
• Not ovulating
• Pregnancy

These lists show what a result "might" mean; they do not make a diagnosis. Your doctor interprets FSH together with your age, your symptoms and other hormone results such as LH and oestrogen.

How is the test done and what affects the result?

Blood is taken from a vein in the arm; it usually takes less than five minutes (MedlinePlus). There are also home FSH urine tests; these can only show higher-than-normal FSH and should not be used to make decisions about fertility (MedlinePlus).

Things that can affect the result:

• Day of the cycle: In women who have periods, FSH changes during the month (MedlinePlus).
• Combined hormonal contraception or high-dose progestogen: While using these, an FSH test is not used to identify menopause (NICE).
• Hormone therapy: It can raise FSH (MedlinePlus).

When should you see a doctor?

• If you have not got pregnant despite trying regularly for 12 months (MedlinePlus says an FSH test may be requested in this case)
• If you have missed 3 periods in a row or your periods have become irregular (NHS)
• If menopause symptoms started before the age of 45
• If you want to know what your FSH result means

Frequently asked

Does high FSH mean you cannot get pregnant?

High FSH on its own does not mean "you cannot get pregnant". The result is assessed together with your age, the day of the cycle it was measured on and other tests. Home urine FSH tests do not show fertility (MedlinePlus). If you are planning a pregnancy, discuss the result with your doctor.

Does high FSH mean menopause?

At 45 and over, high FSH together with symptoms is usually a sign of normal perimenopause or menopause (MedlinePlus). At a younger age, causes such as early failure of the ovaries are also considered; according to NICE, this diagnosis is made not from a single test but from two blood samples taken 4–6 weeks apart.

Are FSH and AMH the same thing?

No. FSH is released by the pituitary gland and changes throughout the month. AMH reflects the number of eggs remaining in the ovaries. NICE recommends not using an AMH test to identify menopause in people aged 45 and over. We explain AMH in the Menopause Glossary.