Menstrual cycle information

What is the menstrual cycle?

The menstrual cycle begins when you get your period. This is when you shed the lining of your uterus (womb), preparing your body for a possible pregnancy. A typical cycle lasts between 24 and 38 days and it’s divided into several phases.

Hormone levels fluctuate significantly during the menstrual cycle, so it’s important you take a hormone blood test during the correct phase so that your results are interpreted accurately.

When should I take my test?

For tests containing LH, FSH, or oestradiol, you should aim to take your test between days two and five (ideally day three) of your menstrual cycle.

For progesterone tests that assess ovulation, you should aim to take your test seven days before your next period is due (or day 21 if you have a 28-day cycle). For pregnancy progress tests, you can take your progesterone levels at any time. 

What if I don’t have periods or my periods are irregular?

There are many reasons why some women have irregular or absent periods, such as:

• Being pregnant
• Breastfeeding
• Polycystic ovary syndrome (PCOS)
• Thyroid conditions
• Pituitary conditions
• Medications, including hormonal contraceptives
• Excessive exercise
• Stress
• Being under- or overweight
• Perimenopause

This can make it challenging to know when to take a hormone test, as well as which menstrual cycle phase you’re in. If this is the case for you, it is reasonable to take the test at any time. However, please make us aware in the supporting information section or let your practitioner know that you have irregular periods.

How do I submit my last menstrual period (LMP)?

As soon as you’ve taken your sample, log in to MyMedichecks and click on the relevant test. Here, you can tell us the date of your last menstrual period and answer any other questions relating to the test. Don’t forget to save your entry.

Important: you won’t be able to enter this information once your results are being processed, so please fill this in as soon as you’ve taken your sample.

Why can’t I enter my last menstrual period (LMP)?

If you log in to MyMedichecks and find you can’t enter the date of your last menstrual period, it’s likely we‘ve already started processing your results. Don’t worry, the doctor will still report your results, assuming you took your sample on the dates instructed. They’ll also give normal ranges for other phases of the menstrual cycle if you didn’t manage to take the sample on the correct date.  

What happens if I don’t enter a date for my last menstrual period (LMP)?

If you don’t let us know the date of your last menstrual period, the doctor will interpret your result assuming you took your sample on the correct date (day 3 for LH, FSH, and oestradiol, or day 21 for progesterone).

Your result also won’t appear as red or green on the results status bar, as we can’t be sure which menstrual cycle phase you were in when you took your sample.

If you forgot to enter a date, use the instructions below to find out which menstrual cycle phase you were in when you took your sample. We'll provide normal ranges for each phase with your results.

What happens if I don’t tell you my menopause status?

Our doctors won’t assume your menopause status based on age alone because this can vary greatly between individuals. They will interpret your results as best they can, using the information available. Sometimes, your hormone levels might suggest you are postmenopausal, but menopause isn’t usually diagnosed by a blood test alone. If you are in the perimenopausal phase, hormone levels fluctuate significantly – which can make results more difficult to interpret.

What happens if I give the wrong date for my last menstrual period (LMP)?

If you enter the wrong date, the doctor will interpret your results based on that date, which might lead to an inaccurate interpretation. Please double-check the date of your last menstrual period before submitting it.

If you think you've entered the wrong date, use the instructions below to find out which menstrual cycle phase you were in when you took your sample. We'll provide normal ranges for each phase with your results.

Why can I not see the status bar for my hormone results?

If you don’t submit the date of your last menstrual period, we no longer show your result as red (abnormal) or green (normal) on the results status bar, because we can’t be sure which normal range to apply to your result. We will give your numerical results along with normal ranges for each phase of the menstrual cycle.

How do I calculate my menstrual cycle phase?

The table below can help you work out what days you’re likely to be in each phase. Bear in mind, that each phase can vary from cycle to cycle.

How do hormone levels change during the menstrual cycle?

Sex hormone levels, as well as the normal reference ranges, fluctuate during the menstrual cycle.

Follicle-stimulating hormone (FSH) – FSH levels rise at the beginning of the follicular phase to stimulate the growth of ovarian follicles.

Luteinising hormone (LH) – LH levels remain low during the follicular phase but surge just before ovulation (around day 14), triggering the release of the egg.

Oestradiol – Oestradiol levels rise during the follicular phase as the follicle grows and peak just before the LH surge. After ovulation, oestradiol levels decline slightly but rise again during the luteal phase.

Progesterone – Progesterone levels are low during the follicular phase and rise significantly after ovulation during the luteal phase. This hormone prepares the uterine lining for the potential implantation of a fertilised egg.

What do my results mean if they are abnormal?

Oestradiol

Low result: This could be due to various factors such as excessive exercise, sudden and extreme weight loss, malnutrition, stress, premature ovarian insufficiency (POI), or pituitary conditions. It may also be a normal occurrence if you are using progesterone hormone contraception. If you have been experiencing missed periods or have concerns about your fertility, please consult your regular doctor. Persistently low oestradiol levels can lead to issues with bone strength, so we recommend getting a follow-up test in three to six months to check if it remains low.

High result: Causes of high oestradiol include medications such as hormone replacement therapy (HRT), being overweight, excessive alcohol consumption, liver disease, and stress. Some ovarian tumours can release oestrogen, but this is rare. In women, high oestradiol levels can lead to acne, constipation, decreased sex drive, and low mood. If your result is unexpected, you took a finger-prick test and you use hormonal gels, creams, or pessaries, it's possible that your result may be falsely elevated due to skin contamination. This can occur if your testing finger has been in contact with any hormonal gels, or even if you have been in contact with someone using these products in the last four weeks. If you believe this applies to you, we recommend arranging a repeat test.

Find out more about oestradiol.

Luteinising hormone (LH)

Low result: There are multiple reasons for having a low LH level. These may include stress, intense exercise, rapid and excessive weight loss, malnutrition, being underweight, hypothyroidism, and issues with the pituitary gland. In women using hormonal contraception, a low LH level may be a normal and non-concerning occurrence.

High result: A high LH level can be caused by conditions such as polycystic ovary syndrome (PCOS) or a decrease in egg production. We suggest getting another hormone test in a few months. If the result continues to rise, it could indicate perimenopause. If you have symptoms of PCOS, like irregular periods, excessive body hair, acne, or fertility issues, we recommend speaking to your doctor and possibly checking your testosterone levels.

 Find out more about LH.

Follicle-stimulating hormone (FSH)

Low result: A low FSH level can be caused by stress, hormonal contraceptives, rapid weight loss or being underweight, lack of ovulation, pregnancy, and pituitary gland problems.

High result: This might indicate that the ovaries are producing fewer eggs. We suggest getting tested again in a few months. If your FSH level continues to rise, it could be a sign that menopause is approaching. Other potential causes of elevated FSH levels include thyroid or adrenal gland conditions, as well as polycystic ovary syndrome.

Find out more about FSH.

A combination of high FSH, high LH, and low oestradiol levels

This combination of results indicates that you may be entering menopause. If you are experiencing menopausal symptoms that are impacting your quality of life, it's advisable to discuss your options with your GP. For additional information on menopause, including lifestyle adjustments and tips, please visit our menopause blog.

If these results are unexpected, please consider retesting in four to six weeks. If the results remain consistent, this confirms the onset of menopause. If you are under 45 years old, we suggest discussing this with your doctor to explore whether you should initiate hormone treatment to manage some of the long-term risks of low oestrogen, such as osteoporosis.

Progesterone

High result: High progesterone levels can be caused by progesterone supplements, adrenal gland issues, ovarian cysts, or pregnancy, including ectopic pregnancies.

Low-normal result (5-30 ng/ml): A low-normal progesterone result (5–30 ng/ml) can’t confirm whether ovulation has occurred as it falls into a grey zone. We can be more certain if the result is greater than 30 ng/ml. If you receive a low-normal result, you may want to consider repeating this test in a future cycle. If you have concerns about your fertility, it's best to discuss them further with your doctor. You may also find our fertility health hub useful.

Low result: Your progesterone result is low, which means it’s unlikely that you’ve ovulated. There are many potential causes for low progesterone, including stress, excessive exercise, high prolactin, polycystic ovary syndrome, and thyroid problems. We have several tests available to investigate these last three causes.

Find out more about progesterone.