40 Day Menstrual Cycle: Is There Something Wrong?

The average menstrual cycle lasts 28 days – but of course, not everyone’s cycle is “average”! A normal menstrual cycle can last anywhere from 21 to 35 days, but some women find theirs lasting as long as 40 days at a stretch. What does a 40 menstrual cycle mean? Let’s break look at some of the reasons you might have a 40-day long cycle, and what it could mean for your fertility.

What causes a 40-day menstrual cycle?


The usual cut-off for a “normal” menstrual cycle is 35 days. If your cycle lasts more than 35 days, it is oligomenorrhea: a medical term for infrequent menstrual periods.

The most obvious sign of your menstrual cycle ticking over is when you get your period. But another big highlight of your cycle – ovulation – is just as important. Once a month, your ovaries mature one ovarian follicle containing this month’s egg, which is released when you ovulate at mid-cycle.

The follicle growth usually takes 13 to 15 days, but not always. When there are variations in cycle length, it’s usually down to how long it takes this egg-laden follicle to grow. So if you have very long cycles or oligomenorrhea, a longer phase of the follicle growth than usual can be its cause.

Problem in HPO axis

The development of each cycle’s egg depends on follicle-stimulating hormone (FSH). The pituitary gland secretes FSH when the hypothalamus gives the pituitary gland a direction to do so, and FSH acts on the ovary to help follicular maturation. This relationship is called the hypothalamus–pituitary–ovarian (HPO) axis.

Any problem in this HPO axis can result in irregular menstruation, leading to long gaps of 40 days or more between menstrual bleeds. The problem in HPO axis could be down to causes like emotional stress and nutrient deficiency, but you’ll need to speak to a doctor or gynecologist to identify the cause.

Polycystic ovary syndrome

A 40-day menstrual cycle can be caused by polycystic ovary syndrome (PCOS). PCOS is a hormonal disorder in which the ovarian follicles grow too slowly and ovulation may stop.

Perimenopause (approaching menopause)

As you get older and the supply of dormant eggs in your ovaries begins to run dry, your periods become lighter and longer-spaced in the lead-up to menopause. Perimenopause symptoms like longer intervals between menstruations often begin in one’s 40s, although some women notice this change as early as their 30s.

Eating disorders

A lack of adequate calories or nutrients in your diet can lead your mind, body and spirit through the wringer. If your body thinks it’s starving, it puts the kibosh on ovulation and sometimes menstruation altogether.

Oligomenorrhea can be caused by eating disorders like anorexia nervosa and bulimia – mental illnesses that can affect people of any age, gender, race or class. If you think this might be the reason for your menstrual irregularities, don’t hesitate to speak to a doctor, counselor or social worker to get the help you need.

Can I get pregnant with a 40-day menstrual cycle?

woman question
If you’re still ovulating normally, it is possible to get pregnant naturally even if your cycle lasts 40 days. However, even if you are ovulating normally, long or irregular cycles can make it hard to predict what point of your cycle you’ll be fertile, so it’s often a big headache for couples when they’re trying to conceive.

You may want to consider seeing a fertility specialist to identify the cause of your long cycles. Hormonal treatments are also available to kickstart the ovulation process.

I’m not pregnant, but it’s 40 days since my last period. What now?

doctor hospital clinic
Whether your menstrual cycle has always been on the long side or it’s only gotten longer recently, it’s a good idea to see a gynecologist if your cycles last 40 days or more – particularly if you’re thinking of trying to conceive.

Long cycles can point to underlying issues with your reproductive system, some of which, like PCOS, can really benefit from earlier diagnosis and treatment. Make a point of seeing your doctor if you notice irregularities in your menstrual cycle.

Support healthy hormone balance for a 40-day menstrual cycle

woman smile relax healthy

If you cycles are 40 days or longer, it often points to an underlying hormonal issue – meaning it’s a good idea to go for a check-up with your healthcare provider. While you don’t exactly have conscious control over your hormone level, you’re not necessarily powerless, either.

By eating a balanced diet and following a lifestyle that keeps your stress levels under control, you can help support your reproductive hormones. Make sure you’ve got space in your life for some “Me Time” – whether that’s best spent chatting with your friends or partner, catching up on your favorite shows, or enjoying heavy metal shows. Self-care strategies like this can help keep your stress levels under control.