Why the second day of your period is always the worst, according to doctors

Brain fog, period cramps and lower back pain – it’s day two of your menstrual cycle (Picture: Getty Images)

Raise your hand if you’ve ever been victimised by day two of your period.

I know I have.

Over the years, I’ve had to take days off work and take constant painkillers to deal with the cramps, which consistently tend to feel the worst on day two. 

It’s also the day I feel the most fatigued and cloudy. Brain fog is real on your period, and day two is a stark reminder of that.

If you relate, you’re not alone – but it might surprise you to know there’s a scientific reason for it for those terrible day twos…

It’s all hormonal, baby

The ultimate day two care package (Picture: Getty Images)

The main reason the dreaded day two of your menstrual cycle is so horrendous is down to hormones – specifically, prostaglandins, which appear when your progesterone levels lower.

‘As the lining of your uterus breaks down, prostaglandins (hormone-like chemicals) are released in the body,’ Dr Fatema Mustansir Dawoodbhoy, academic doctor specialising in obstetrics and gynaecology, who works with the upcoming period care app Joji, tells Metro.co.uk.

Excess prostaglandins are thought to be the main reason for those pesky cramps you feel as they encourage the uterus to contract, ‘helping to shed the old endometrial tissue released from your body as period blood,’ Dr Fatema explains. 

‘The prostaglandins also constrict the blood vessels in the uterus, reducing the amount of oxygen the uterine tissue receives, and this leads to cramping and pain,’ she adds.

The number of your prostaglandins peak on the second day of your period, which is why the pain seems to peak then, too.

Dr Emilie Côté MRCOG, an obstetrics and gynaecology doctor and researcher who also works with Joji, tells Metro.co.uk that other hormonal changes during the first few days of the menstrual cycle can also affect our perception of pain. 

As well as progesterone, oestrogen levels also drop at the beginning of your cycle.

‘This means that other painful conditions like migraines or fibromyalgia can worsen when you have your period, as the hormone oestrogen falls to its lowest level,’ she says. 

The fact that your flow is typically heavier on the second day of your cycle also contributes to more painful cramps, explains Dr Ashfaq Khan, a consultant obstetrician and gynaecologist and founder of Harley Street Gynaecology.

He tells Metro.co.uk: ‘The second day of the period is typically associated with a heavier menstrual flow for many women. 

‘The increased blood volume can lead to more intense cramping and discomfort as the uterus works harder to expel the menstrual blood.’

So there you have it: the second day of your period is, scientifically speaking, the worst. 

You’re not going crazy! Get some rest and grab a hot water bottle, you’ll feel better tomorrow. 

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It’s not all in your head.