WHAT IS A LH AND FSH BLOOD TEST FOR A WOMAN?

Your hormones play an essential role in controlling the menstrual cycle, ovulation, and fertility. Two of the most important hormones for women are luteinising hormone (LH) and follicle stimulating hormone (FSH). Together, they regulate how your ovaries function and how your reproductive system responds throughout the menstrual cycle.

A blood test measuring LH and FSH levels provides valuable information about fertility, menopause, and overall hormone health. At One Day Tests, this can be done quickly and conveniently through our Female Hormone Blood Test. You can choose a local clinic or a home testing option and receive fast, reliable results within 24 to 48 hours.

Luteinising hormone and follicle stimulating hormone are both made by the pituitary gland, a small gland at the base of the brain. These hormones form part of a system known as the hypothalamic pituitary ovarian axis, which connects the brain and reproductive organs through a feedback loop of hormone signals.

FSH helps your ovaries produce eggs and stimulate oestrogen production. LH works alongside FSH to trigger ovulation and support progesterone production after an egg is released. Testing both hormones together provides a more complete picture of how your body is functioning.

Doctors often recommend checking LH and FSH levels together to investigate issues such as fertility problems, irregular menstrual cycles, or symptoms of early or delayed menopause. Measuring both hormones helps reveal whether the problem lies in the ovaries themselves or in the brain’s control of reproductive function.

FSH and LH work together to manage the menstrual cycle. In the first half of the cycle, FSH stimulates small sacs in the ovaries called follicles. Each follicle contains an immature egg, and under the influence of FSH, one follicle grows and prepares to release a mature egg.

As the follicle grows, it produces oestrogen, which signals the brain to release a surge of LH. This LH surge triggers ovulation, when the egg is released from the ovary. After ovulation, LH helps maintain the corpus luteum, a temporary gland that produces progesterone to prepare the womb for a possible pregnancy.

Hormone levels rise and fall in a predictable pattern. When these patterns are disrupted, it can point to certain health conditions. For example, unusually high FSH levels may indicate menopause or reduced ovarian reserve, while persistently low levels may suggest a problem in the pituitary or hypothalamus.

Doctors may recommend LH and FSH blood tests for several reasons. One of the most common is to investigate fertility concerns. These hormones help determine whether ovulation is occurring normally and whether the ovaries are functioning as expected.

Testing is also useful for identifying causes of irregular or absent periods, known as oligomenorrhoea or amenorrhoea. High or low LH and FSH levels can also provide clues about early menopause or primary ovarian insufficiency, especially in women under 45 who experience symptoms such as hot flushes or missed periods.

Another reason for testing is to help diagnose polycystic ovary syndrome (PCOS). In women with PCOS, the LH to FSH ratio is often higher than normal, sometimes greater than 2.5 to 1. This imbalance affects ovulation and can make conception more difficult.

Doctors may also use these tests to identify problems with the pituitary or hypothalamus, which can interfere with hormone production. However, for women over 45 with typical menopause symptoms, hormone testing is rarely necessary because diagnosis is usually based on symptoms rather than blood results.

No fasting or special preparation is required before this test, but timing matters. For most women, LH and FSH are measured in the first few days of the menstrual cycle, usually between days one and five, when hormone levels are at their baseline.

If your doctor also wants to confirm ovulation, a separate progesterone test is usually taken around day 21 of a 28 day cycle, or seven days after ovulation in women with irregular cycles.

It is important to note that hormonal contraception can affect LH and FSH results, as it alters your body’s natural hormone levels. If you are taking hormonal contraception or hormone replacement therapy, you may be advised to stop temporarily before the test. Always check with your doctor first, as you may still need to use a barrier method for contraception.

You do not need to fast before your appointment, but it is worth mentioning if you take high doses of biotin supplements, as these can interfere with hormone measurements.

The test itself is simple. A small blood sample is taken from your arm, or you can use a home finger prick kit provided by One Day Tests.

Hormone levels vary throughout the menstrual cycle, and different laboratories may use slightly different reference ranges. Your doctor will interpret your results based on your cycle and symptoms to provide accurate guidance.

Typical LH and FSH ranges are as follows:

If both LH and FSH are high, it often indicates that the ovaries are not responding properly, which is common in menopause or ovarian insufficiency. If both are low, this may point to a problem in the pituitary gland or hypothalamus, suggesting that the brain is not sending the right signals.

A raised LH level with normal FSH is often seen in polycystic ovary syndrome. In all cases, doctors consider these hormone results alongside other tests, such as oestrogen, prolactin, testosterone, and thyroid hormones, to form a complete picture.

Sometimes a single test is not enough to give a full picture of your hormone health. For example, if your doctor suspects early menopause or primary ovarian insufficiency, LH and FSH levels should be measured twice, at least four to six weeks apart.

Additional tests such as oestradiol, prolactin, thyroid stimulating hormone (TSH), and testosterone may also be ordered to assess the wider hormonal pattern.

If results are abnormal or symptoms persist, your GP may refer you to a gynaecologist or endocrinologist for further investigation and specialised care.