Periods are known for throwing some curveballs. You might find that you have to use the bathroom (much) more frequently on your period or even that your period blood has a peculiar smell — but there may be nothing less predictable than the color of your flow from one day to the next. Period blood ranges from pink to dark red to black, and if you don't understand what causes these changes, they can be unsettling. Fortunately, a range of period colors is not only normal, but expected.
"The color of period blood is really determined by how long the blood has remained in your uterus and vagina," Janelle Mary Jackman, MD, FACOG, a board-certified ob-gyn and minimally invasive reproductive surgeon, tells POPSUGAR. "It gets darker due to the oxidization of blood — the longer it stays around before it is discharged."
The duration, flow, and even the color of your period is extremely individual, but California-based ob-gyn Kendra Segura, MD, MPH, FACOG, explains that periods will often start out pink on the first day, then turn bright red for a few days, followed by dark red on the heaviest day, and finally, brown or black for the remaining day or two. POPSUGAR asked the experts what each of these different period colors mean, so you know exactly what to expect.
Pink Period Blood
"Pink blood is usually present at the onset of menses as fresh blood mixes with vaginal mucus and discharge, making it a lighter hue," Dr. Jackman says. Additionally, if you have a lighter flow, you may see pink blood throughout your period simply because the blood isn't shedding as quickly or as steadily.
Bright Red Period Blood
Like that pink hue, bright red blood is typically seen toward the beginning of your period, when the blood is freshest. "As one's uterus contracts and the flow gets steadier, the blood sheds quicker as the cycle continues," Dr. Jackman explains. "This makes the blood a more crimson red as it does not oxidize due to quick explosion." In this case, "explosion" refers to the faster rate at which the blood leaves the uterus and vagina.
Dark Red Period Blood
As you may have guessed, blood that's a darker shade of red is older than the bright red blood seen toward the beginning of your period. While blood will typically grow darker as your cycle progresses, it can also appear darker if it's been "sitting in your uterus" for some time, according to Dr. Segura. Dark red blood is most often seen in the morning or after you've been laying down for a while — because the longer it takes for the blood to pass through the uterus, the more time it has to oxidize.
Dr. Segura notes that dark red blood could also be an indication of a passing blood clot, which is similar in color. If you have a heavier flow, you may also see more dark red blood compared to those with lighter periods.
Brown Period Blood
Brown period blood is usually seen at the very end of your period, just before before the bleeding stops completely. "The blood can look extremely dark — brown or even black — if it has taken longer to exit the vagina," Dr. Jackman says. "This is blood that has had a lot of time to oxidize; thus, its dark appearance." Dr. Segura adds that, if you notice brown discharge at the beginning of your period, it's likely just blood that was left over from the previous cycle. No need to be concerned.
Black Period Blood
Think of black discharge as your period's finish line. "Although this may look alarming, it isn't a reason to panic," Dr. Segura explains. "Red blood that turns black means that the blood has been oxidized. Hence, it's been in your uterus for awhile and we call it 'old blood.'" Again, this will usually occur at the end of your period, when your flow has slowed down significantly.