Living life can be tiring, amirite? But if the week of your period leaves you feeling exhausted, it’s worth knowing that there’s a real, scientific reason behind your sleepiness.

Aside from dealing with the cramps, headaches and bloating that come as standard for many women on their period, there’s plenty of science stuff at play that will take it out of you, too. Good Housekeeping spoke paediatrician Dr. Molly O’Shea, who explained that it’s normal to feel totally knackered for a week of every month.

“In the 10 days or so before your period, your body is geared up in the hopes that the egg you sent down the old fallopian tube met some sperm there and landed in a plush uterus ready to grow a baby,” she explained.

“When your uterine lining isn’t invaded by a fertilised egg, the hormones sustaining the environment aren’t needed anymore and the hormone levels plummet. When this happens, your body goes from high alert to nothing hormonally and that shift causes other changes too and all of those changes are exhausting. Until your hormone levels increase again, you are really tired.”

There’s not much you can do about your body’s natural cycle, but the good news is that your energy levels tend to peak during ovulation, which is generally about two weeks after the start of your period.

There are natural ways of helping your body out when its feeling tired though; drinking water, getting at least eight hours sleep and exercising is all useful, general advice. But according to Nicole Telfer, Science Content Producer at period tracking app Clue, there are different ways to overcome your tiredness depending on what's causing it.

"People who experience premenstrual and menstrual symptoms may report disrupted sleep," Nicole tells Cosmopolitan. "This can be from pain (cramps or headaches) or from increased fatigue or insomnia. Using pain alleviating medications may help restore sleep quality by relieving pain."

If you have a premenstrual mood disorder, the expert suggests you're "more likely to experience sleep disturbances like insomnia, hypersomnia, fatigue, and even disturbing dreams during the luteal phase (the second part of the menstrual cycle) which could be due to disruption in circadian rhythms." In order to overcome this, Nicole explains that some researchers suggest using light therapy may help people with severe cases, but more research in the area is needed.

People with PCOS (polycystic ovary syndrome) are more likely have sleep disordered breathing like sleep apnea or snoring if they are obese, which in turn impacts sleep quality. "These people would benefit from seeing a healthcare provider specialising in sleep," advises the expert.

But if you’re generally feeling low, and nothing seems to be shifting it? Remember that a good old day in bed, a bar of chocolate and Netflix can work wonders.