Whether you are trying to conceive naturally, considering IVF, preserving your fertility, or simply want to understand your reproductive health, fertility blood tests are often the first step in your fertility journey.

These tests provide valuable insight into how your ovaries are functioning, whether you are ovulating regularly, and whether hormonal conditions could be affecting your ability to conceive.

At Oocyt, we believe that understanding your fertility empowers you to make informed decisions about your reproductive future. While blood tests cannot tell the whole fertility story, they provide essential information that helps fertility specialists develop a personalised treatment plan.

In this guide, we'll explain the most common fertility blood tests, what they measure, how to interpret the results, and what they could mean for your chances of conception.

Why Are Fertility Blood Tests Important?

Hormones are chemical messengers that control almost every aspect of reproduction.

They regulate:

• Egg development

• Ovulation

• Menstrual cycles

• Implantation

• Pregnancy maintenance

• Ovarian function

Even small hormonal imbalances can affect fertility.

Blood tests help fertility specialists identify:

• Ovulation problems

• Reduced ovarian reserve

• Polycystic Ovary Syndrome (PCOS)

• Premature ovarian insufficiency

• Thyroid disorders

• Elevated prolactin

• Hormonal causes of irregular periods

For couples struggling to conceive, blood tests often provide the first clues about why pregnancy has not yet occurred.

When Should Fertility Blood Tests Be Done?

Many people believe they must try for a year before seeking fertility investigations. While this advice applies to many healthy couples under 35, there are situations where testing should be considered much earlier.

You should consider a fertility assessment if you:

• Are over 35 and have been trying for six months.

• At any point if you have irregular or absent periods.

• Have a history of endometriosis or PCOS.

• Have experienced recurrent miscarriage.

• Have had pelvic infections or surgery.

• Have previously undergone chemotherapy or pelvic radiotherapy.

• Have a family history of early menopause.

• Are considering delaying parenthood and wish to assess your ovarian reserve.

• Are planning fertility preservation, including egg and sperm freezing.

Early testing can help identify concerns before they become more difficult to manage.

Preparing for Fertility Blood Tests

Some fertility hormones change throughout the menstrual cycle, meaning timing matters.

Your fertility specialist will advise the best day for each test.

Certain medications, hormonal contraception, pregnancy, breastfeeding, and some medical conditions can influence hormone levels, so it's important to tell your healthcare provider about any medications or supplements you are taking.

Anti-Müllerian Hormone (AMH)

What is AMH?

Anti-Müllerian Hormone (AMH) is produced by small developing follicles within the ovaries.

Because these follicles contain immature eggs, AMH provides an estimate of your ovarian reserve which is the number of eggs remaining in your ovaries.

Unlike many other fertility hormones, AMH can usually be measured at any point during your menstrual cycle because it remains relatively stable throughout the cycle.

Why is AMH Tested?

AMH helps fertility specialists:

• Estimate ovarian reserve

• Predict response to IVF stimulation

• Individualise medication doses

• Assess suitability for egg freezing

• Identify women at increased risk of ovarian hyperstimulation syndrome (OHSS)

• Support the diagnosis of PCOS

What Do High AMH Levels Mean?

Higher AMH levels often suggest:

• A larger ovarian reserve

• Polycystic ovaries

• Increased response to fertility medication

However, higher is not always better.

Women with very high AMH levels may be at increased risk of OHSS during IVF treatment.

What Do Low AMH Levels Mean?

Lower AMH levels suggest fewer remaining eggs.

This may occur due to:

• Increasing age

• Previous ovarian surgery

• Endometriosis

• Premature ovarian insufficiency

• Chemotherapy or radiotherapy

A low AMH result does not mean pregnancy is impossible.

Many women with low AMH conceive naturally or through fertility treatment.

The quality of the remaining eggs often matters more than the quantity.

Common Misconceptions About AMH

One of the biggest myths in fertility medicine is that AMH predicts whether you can become pregnant naturally.

It does not.

AMH cannot tell us:

• Whether you are ovulating

• The quality of your eggs

• Whether your fallopian tubes are open

• Whether sperm can fertilise the egg

• Whether implantation will occur

It is one piece of a much larger fertility picture.

Follicle-Stimulating Hormone (FSH)

FSH is produced by the pituitary gland and stimulates the ovaries to grow follicles each month.

It is usually measured between Days 2 and 5 of the menstrual cycle.

When ovarian reserve declines, the brain produces more FSH in an attempt to stimulate the ovaries.

Persistently elevated FSH may suggest diminished ovarian reserve, although results should always be interpreted alongside AMH and ultrasound findings.

Luteinising Hormone (LH)

LH is responsible for triggering ovulation.

Shortly before ovulation, LH rises sharply, causing the mature egg to be released from the ovary.

Persistently elevated LH may occur in women with PCOS, while low levels may indicate disorders affecting the pituitary gland or hypothalamus.

LH is often interpreted together with FSH rather than in isolation.

Estradiol (E2)

Estradiol is the main form of oestrogen produced by developing ovarian follicles.

It plays an important role in:

• Follicle development

• Thickening the uterine lining

• Preparing the body for pregnancy

High early-cycle estradiol can sometimes mask an elevated FSH level, which is why both hormones are measured together.

Progesterone

Progesterone is produced after ovulation by the corpus luteum.

Its main role is preparing the lining of the uterus for implantation.

A progesterone blood test confirms whether ovulation has occurred.

The timing of this test is critical.

Rather than automatically testing on Day 21, progesterone should ideally be measured approximately seven days after ovulation.

For women with longer or shorter cycles, this may fall on a different day.

Prolactin

Prolactin is the hormone responsible for breast milk production after childbirth.

Outside pregnancy, elevated prolactin may interfere with ovulation and menstrual cycles.

High prolactin levels may be caused by:

• Certain medications

• Pituitary adenomas

• Thyroid disorders

• Stress

• Breastfeeding

Fortunately, many causes are treatable.

Thyroid Function Tests

The thyroid gland has a profound influence on fertility.

Even mild thyroid dysfunction can affect:

• Ovulation

• Menstrual regularity

• Egg quality

• Miscarriage risk

• Pregnancy complications

Your fertility specialist may request:

• Thyroid Stimulating Hormone (TSH)

• Free T4

• Occasionally thyroid antibodies

Treating thyroid disease often improves fertility outcomes.

Additional Blood Tests Your Fertility Specialist May Recommend

Depending on your medical history, additional investigations may include:

Vitamin D

Low Vitamin D levels are common worldwide and may affect reproductive health and pregnancy.

Full Blood Count

Checks for anaemia or infection.

HbA1c

Screens for diabetes or pre-diabetes.

Infectious Disease Screening

Prior to fertility treatment, screening is usually performed for infections such as HIV, hepatitis B, hepatitis C, and syphilis to ensure the safety of both patients and laboratory procedures.

Rubella and Varicella Immunity

These blood tests determine whether you have immunity to infections that could be harmful during pregnancy.

Vaccination may be recommended before treatment if immunity is absent.

Can Blood Tests Diagnose Infertility?

No.

Blood tests provide valuable information but cannot diagnose infertility on their own.

Fertility specialists also consider:

• Semen analysis

• Pelvic ultrasound

• Tubal patency tests (HyCoSy or HSG)

• Medical history

• Lifestyle factors

• Age

• Previous pregnancies

Every result forms part of a much bigger picture.