A fertility blood test is used to measure your hormone levels and is usually the first fertility test that your doctor will prescribe if you are finding it difficult to conceive and suspect that you may be infertile.
Blood test results are primarily used to detect hormonal causes of infertility. The blood test is taken at the start of your menstrual cycle (days 2 to 5) and typically measure levels of the hormones FSH, LH, oestradiol and sometimes prolactin.
It is a relatively easy way of identifying why it is taking you some time to get pregnant and in some cases, this may be enough to pinpoint the root of the problem.
Blood tests are often performed alongside a semen analysis which allows your doctor to find out whether the problem is due to male or female-related fertility problems.
LH and FSH levels
Determining the ratio of FSH to LH will allow your doctor to find out whether you may have Polycystic ovary syndrome (PCOS). The ratio of LH to LH should be around 1:1 and if the level of LH is more than double FSH, this may indicate a hormonal imbalance that is often observed in PCOS. If there is reason to believe that this is the case, then the next step is an ultrasound scan to confirm the diagnosis.
Unlike other hormones, the level of prolactin in your blood can be observed at any point in the menstrual cycle. Abnormally high prolactin levels can lead to problems with ovulation.
Testing your ovarian reserve
Ovarian reserve testing is routinely offered to women who are considering fertility treatments such as IVF. Ovarian reserve can be assessed either by FSH levels or by an AMH test. Doctors can use your ovarian reserve can give an indication of how well you may respond to the medication used to stimulate your ovaries in IVF treatment.
Progesterone blood test
A progesterone blood test is normally performed midway through your luteal phase, this will allow your doctor to see whether you have ovulated and whether the corpus luteum is secreting the expected levels of progesterone. Progesterone prepares the womb for the implantation of the fertilized egg. The test is often measured on day 21, but this will depend on how long your cycles are and when you ovulate in your cycle.
Thyroid hormone blood test
This blood test can be performed at any point in your menstrual cycle. Abnormal levels of thyroid hormone (TSH) can affect your menstrual cycle and your chances of getting pregnant. If a problem is found, medication can be taken to help manage your thyroid levels which will improve your fertility.
Tests for sexually transmitted diseases
Chlamydia can damage the Fallopian tubes and prevent the egg from moving through the tubes, which can significantly reduce female fertility levels. If a blood test indicates the presence of a high number of anti-chlamydia antibodies, both you and your partner will need to be treated with a course of antibiotics.