Decoding the Different Colors of Period Blood

Most people who menstruate know that there’s no such thing as a “normal” period. Everything from when it comes to how long it stays can change month-by-month — but what about color? What does it mean when one day your blood is a rich red color, and the next day it’s almost black? We spoke with some OB-GYNs to find out what’s happening and what it all means.

What’s going on?

Before going any further, it might be helpful to have a quick refresher on what happens during your period.

Every month, your brain signals your body to produce hormones to prepare your body for a potential pregnancy, Dr. Patricia Lo, an OB-GYN at MemorialCare Saddleback Medical Center in Laguna Hills, California, tells SheKnows. These hormones, specifically estrogen, cause the lining of the uterus to thicken with extra blood and tissue. 

Usually mid-cycle, one of the ovaries will release an egg (ovulation), while during the second part of the menstrual cycle, progesterone levels increase to stabilize the lining of the uterus, Lo explains. The egg then gets picked up by one of the fallopian tubes and travels toward the uterus. If the egg is not fertilized by sperm, pregnancy does not occur, and the lining of the uterus breaks down and flows out of the vagina during your period.

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But why the different colors?

Depending on the thickness of the lining of the uterus, menstrual blood — made up of blood, cells from the lining of the uterus, cervical and vaginal secretions — may differ in color and consistency, Lo says. These additions, along with certain proteins that keep the blood thin and prevent internal clotting, also make period blood different from normal blood in your body.

According to Dr. Laurence Orbuch, OB-GYN, blood changes color depending on how long it has been exposed to oxygen. Blood color appears darker because it has reacted with oxygen, and the majority of the water content in the blood will have also evaporated, giving it a more concentrated pigmentation. 

At the beginning or end of your period, blood can be a dark brown/red shade and can have a thick consistency, Orbuch explains, adding that it’s normal for the first signs of your period to be bright red and less viscous. 

The blood can even appear to be pink at the very beginning of the cycle, Lo says, because it has been diluted with other cervical secretions.

But if your period blood appears brownish at the start of your cycle, that’s normal too, Orbuch notes, explaining that it simply may be older blood that took longer to be expelled from the uterine lining. Blood clots are normal on the heaviest days of your period (typically the second or third day) and can appear deep red or almost black, and appear to contain fibrous-looking tissue, he adds. 

The darkest red — sometimes bordering on dark brown or black — shades are most common at the end of your cycle because the blood has been sitting around longer and has had time to oxidize, Lo explains.

What’s not normal?

Now that we know what we can expect to see during our periods, what should we be on the lookout for that might mean something’s not quite right?

The first is an unusually heavy flow. According to Dr. Pari Ghodsi, an OB-GYN, if you are losing more than 80 milliliters (around one-third cup) of blood over the course of one cycle, that is too much blood. Unfortunately, it’s hard for anyone to actually measure the amount, so if you feel that the heaviness of your cycle is interfering with your life or you become dizzy or lightheaded talk to your doctor, Ghodsi tells SheKnows.

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Dr. Yen Tran, an OB-GYN at Orange Coast Medical Center in Fountain Valley, California, tells SheKnows that if your flow is so heavy that it requires you to have to change your pad or tampon more than seven times a day, you should seek medical attention to see if you have fibroids or endometrial polyps.

As far as colors go, if you have grayish, yellowish or orange discharge, Orbuch says that this can be the sign of an infection or other conditions. 

Similarly, Tran says that any puslike discharge should also be brought to your doctor’s attention.

And while blood clots are totally normal, if you’re getting ones that are the size of quarters or larger, Lo says it may be time to speak with a doctor about those. She also mentions that an abnormal odor could be a sign of infection.

So, the next time you have your period, don't be afraid to look down and pay attention to the color of your blood. It'll hold clues as to the stage of your cycle and potentially let you know if something is off and you should see a doctor.

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