Changes in the colour of your period blood can seem alarming, but they’re totally normal. 

The colour of your period blood simply depends on the length and flow of your period, and can range from light pink all the way to black.

During your period your uterus sheds its old lining (the endometrium) and expels it from your cervix and vagina. The longer it takes for the endometrium to leave your body, the darker it becomes. This is because like all blood, period blood oxidises—meaning the haemoglobin and iron in the blood react to oxygen and gives it a darker colour.

So if you’ve ever looked at your pad or tampon and slightly freaked out at the colour of your period blood, chances are you’re not alone. To put your mind at ease, we break down what the different shades of period blood mean, and if or when they’re cause for concern.

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Pink period blood

Right before your period, small amounts of menses might mix with your cervical mucus and cause a pink discharge. If you spot pink discharge right before you come on your period, it just means there’s more to come. 

However, if you notice pink, watery discharge in between periods, speak to your GP about it as it could be a sign of cervical cancer. While we’re on the subject, if you notice grey or green discharge, it could be an sign of a vaginal infection like BV or STI like trichomoniasis.

Bright red period blood 

This is fresh period blood, and will typically appear at the start of your cycle. It means your menses were expelled quickly, so it can also be common to see this colour if you have a heavy flow, as the volume can push the blood out faster. Although most people lose less than 80ml of blood during their period, if you have a heavy flow you will lose more than that. 

During a heavy period you may also notice blood clots in your menses, this is also normal! Period blood clots are rarely something to worry about, but if you regularly notice clots larger than 2.5 cm (or a 10p coin), it’s worth chatting about it with your GP as they could be caused by conditions such as uterine fibroids or endometriosis.

Dark red period blood

If your period blood is a dark red colour, it means it’s not as fresh. Dark red period blood has likely been in your body for longer, and had a chance to oxidise.

This could be the result of a very thick endometrium (your body thickens your uterine lining to prepare for a possible pregnancy) or just a slower rate of shedding. Either way, totally normal!

Brown period blood

Brown blood is quite common both at the start and end of the cycle. It’s either old menses from your previous cycle that hadn’t been fully expelled, or the last bit of your current period being discharged.

Black period blood

Black period blood might look very goth, but there’s nothing to worry about. Much like brown period blood, this is simply old blood that was chilling in your body for too long.

If your period blood is black, it can also sometimes have the consistency of coffee grounds, which is simply your menses reacting to being exposed to an acidic environment. So if your period blood is black, it probably just means that your period was a little late that month. 

The one colour period blood will never be? Blue—despite what pad commercials might have led you to believe.

TL;DR

• The colour of your period blood can change month on month, and simply depends on how long it takes for your menses to leave your uterus. 
• Period blood can range from light pink to black in colour, and it’s completely normal.
• The only time you should be concerned is if you notice pink discharge in between your periods, or period blood clots larger than a 10p coin.