Pretty much by day two of your very first period, you're accustomed to the sight of blood falling out of your vagina. But life likes to throw us curve balls, and so sometimes—just to mix it up!—period blood looks... different. It shows up when it shouldn't, fails to show up when it should, and on extra special occasions, doesn't look like blood at all.
Before you panic: It's normal for period blood to be another color that isn't red. And as Dr. Rebecca Brightman, an ob-gyn in New York City, reassures, even black period blood isn't atypical or necessarily a cause for alarm. But it's understandable if you freak out a little, because uh, black liquid coming out of your body in any context is wild. Here's everything you need to know about the most metal of all period blood. Rock on.
Why blood looks black
Black period blood isn't a sign that you're pregnant with demon spawn, though that would maybe be cool? Brightman said black-looking period blood almost always comes at the tail end of your period, and is just the result of blood that's been in your body longer.
Periods are your body's way of clearing out the uterine lining in the absence of a pregnancy, and involve sloughing off the thickened lining and shedding it about once a month (hence the bleeding). You ever notice how your blood is bright red at the beginning of your period? That's because, as Brightman said, that blood is fresher, and the result of active bleeding.
But as the sloughing of your uterine lining stops, and your period lightens, blood leaves the body more slowly. And because of that, blood has had time to oxidize, which can make it turn wild colors like dark brown or black. So when you look down and see dark brown or black blood, it's just a sign that it's older and has been in the body a bit longer. "The older the blood, the darker it gets," Brightman said. "The uterine lining has already been sloughed off and you're starting a new cycle. It's residual blood."
Brightman said black or brown-ish blood at the end of a period is something some women experience, and others don't. Typically, it's normal for it to last for up to two days. She said if you consistently see black or dark brown blood at the end of a period for longer than that, you should talk with your doctor.
What if it isn't at the end of your period?
Brightman said some women see dark brown or black blood at the beginning of their period, because, well, everyone is different. She said it could just be a sign that your uterine lining is starting to break down, and some women notice this eerie spotting a few days before the start of a period. If you notice this more than a few days before, Brightman says you should talk to your doctor (but shouldn't feel panicked), just to make sure there's nothing funky going on with your uterus (like polyps).
You should also remain calm and talk to your doctor if you're on hormonal birth control and notice dark spotting in the middle of your cycle. Brightman said women on hormonal birth control typically have thinner uterine lining and often don't get a regular period, but may experience a bit of dark spotting mid-cycle.
Ok, but what if it's actually gray?
Normally I wouldn't begrudge you the difference between gray and black, but when it comes to stuff that's coming out of your vagina, the distinction matters! Brightman said the most common cause for gray discharge is infection. And because of that, if you ever notice gray discharge or blood, you should make an appointment with your doctor.
One infection associated with gray discharge is bacterial vaginosis, which comes with other symptoms like a fishy odor and itching. Another fairly common infection is trichonomiasis, which causes yellow-gray or green-hued discharge, as well as some pain and swelling in the vulva.
So, infection and scare-factor aside, different shades of period blood are Fine and Normal and usually nothing to call your doctor about. Just your body's way of letting you know that it is utterly in charge of you and can scare the shit out of you whenever it pleases. Don't you love it?
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This article originally appeared on Cosmopolitan.com. Minor edits have been made by the Cosmo.ph editors.