Illustration by Marta Pucci
What does the color of your period blood mean?
Your period blood can be brown, black, dark red, pink, or grey
Top things to know about period blood color
Changes in the color of your blood during your period are normal
Dark red, brown, or black period blood is typically red blood that has reacted with oxygen
Talk to your healthcare provider if you have grayish or pink watery discharge, as this could be a sign of an infection or something more serious
Talk to your healthcare provider if your period is different from what is normal for you
You may notice the color of your period blood varies. Sometimes it might be a bit more brown than usual, or almost black, only to turn bright crimson red later.
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Underlying health conditions are more likely to affect the timing and length of your period than its appearance—but there are some reasons why your menstrual blood may vary in color.
Why does my period blood color change throughout my cycle?
Blood (and tissue) changes color depending on how long it has been exposed to oxygen in the air (1). When you cut your skin, the blood from a fresh wound is bright red. If you put a bandage on it and check it the next day, you'll see that the once-red blood has been oxygenated and turned brown. Most of the water in the blood will have evaporated, making the pigmentation even more concentrated (1).
Throughout your period, you can observe blood and other secretions coming out of your vagina, and the color can give you information about your health. Let's talk about this process.
The menstrual cycle is a process that involves your ovaries and your endometrium, but it also affects your entire body (2,3). Your endometrium is the inner lining of your uterus that grows and sheds each cycle (2). It is where a fertilized egg could implant and grow into a pregnancy. The endometrium is made up of highly vascularized tissue (tissue with vessels) with special arteries called spiral arteries (2,3). This makes the perfect environment for a fertilized egg to grow, with quick and easy access to a fresh blood supply (carrying nutrients and oxygen) to begin developing into a fetus (2).
If the egg is not fertilized, a complex inflammatory process occurs just before your period, causing these specialized spiral arteries to constrict and limit blood loss (2,3). For some people, this is when they feel cramping pains. After the spiral arteries constrict, the endometrium loses its blood supply and begins to break apart and separate from the deeper layers of the uterus (2,3).
Contrary to what many people think, your period is not just blood, but a combination of the shed endometrial layer, blood, and vaginal secretions (4). Although it may seem like a lot of blood, the estimated amount of blood people lose during their period is typically less than 80 ml or 3 oz (2). One study showed that the average amount of blood lost during a cycle is about 45 ml or 1.5 oz (5). In comparison, a regular menstrual cup holds about 30 mL (6).
As tissue breaks down, it leaves behind torn ends of blood vessels that continue bleeding (3,4). This is where the bright red blood you may see during your period comes from. Eventually, platelets, pieces of cells involved in blood clotting, are activated to clump together and form a plug to stop the bleeding, ending your period (2,7).
Your uterine lining doesn't separate all at once. It's a slower, controlled separation and it takes time for your uterine lining tissue to make its way down through your cervix and vagina (2). This initial blood and tissue is red at first but may appear dark red or brown because it took longer to leave your body.
As the bleeding slows towards the end of your period, it may appear darker red or brown again. Any shades of red you see during your period will change depending on the balance between the amount of blood and other components and the time they have been exposed to oxygen.
What color is healthy period blood?
Periods will be a combination of blood, endometrial cells, and vaginal secretions, that will vary in color depending on the amount of each of these parts and how long they were exposed to oxygen (1,2). If you bleed regularly, you have probably already seen the shades of blood that are typical for you, in your pad, tampon, cup, or period underwear. For most people, red, dark red, and brown will be typical. If you have bleeding that is much heavier than normal or additional symptoms such as fever or pain, it could be that you are experiencing another medical situation and you should consult a healthcare provider.
What does black period blood mean?
At the end of your period, your period blood may be a dark brown or black color and have a thicker consistency. This is blood that has taken longer to leave your endometrium and has been oxygenated so it is darker in color than the fresher, bright red blood (1,8).
During perimenopause, the transition before menopause, people may have irregular periods (8). This is due to irregular ovulation, hormonal changes and not ovulating every cycle. The inner lining of the uterus gets thicker during this time, which can cause all types of bleeding, from spotting to heavy bleeding (8,9). That is why people in perimenopause may experience changes in their period colors: from pink discharge to thicker, black blood. You can use Clue Perimenopause to navigate the transition to menopause.
What does dark red period blood mean?
Your period flow typically gets heavier on the second or third day of your cycle because the uterine lining is shedding faster. Bright red period blood is newer blood that doesn't have time to darken before it leaves your body. Bright red blood may also be associated with heavy periods and abnormal bleeding (2,9).
Your period is often a reflection of your health in general, where heavy, bright red bleeding that is not common for you, could be a sign that something has changed (8). There are many causes of heavy bleeding, including pregnancy, medication use, bleeding disorders, hormonal imbalances, or anatomical changes such as polyps and fibroids (8). If you soak more than one pad or tampon in an hour, or if you have bleeding that makes you feel weak or dizzy, call your healthcare provider right away (10,8).
What does pink period blood mean?
Your period color may be light red or even pink if there is more water and vaginal secretions in its composition. Bleeding that mixes with fertile cervical fluid may appear light red or pinkish.
Sometimes, watery or pink vaginal discharge that occurs irregularly (without a pattern and not related to your menstrual cycle) may be a sign of endometrial or cervical cancer and should be evaluated by a healthcare provider (11,12).
What is spotting and what color should it be?
Spotting is usually a dark red, brown, or black color.
Spotting is any bloody vaginal discharge that doesn’t require the use of period products, like a pad or tampon. Some people experience mid-cycle spotting, also known as ovulatory bleeding (5,13). Spotting can be associated with several gynecological conditions (9). It may be a sign of anatomical or hormonal abnormalities (9). It could also be a side effect of some types of birth control, such as progesterone-only pills, and can also be associated with testosterone therapy in transgender men (13,14).
What does grey, green, or yellow period blood color mean?
Vaginal discharge of different colors, especially if accompanied by other symptoms, could be a sign of infection.
Bacterial vaginosis or BV, is an overgrowth of normal bacteria that can change the color of your period to gray. BV can also cause vaginal discomforts like itching, a gray discharge, or a fishy odor (15).
Sexually transmitted infections or STIs can also occur with minimal symptoms, such as vaginal discharge and abnormal vaginal bleeding (16). If you think you may have been exposed or have symptoms of an STI, you should contact your healthcare provider.
If you have heavy bleeding with pieces of grayish tissue, this could be a sign of pregnancy loss (17).
Seeing a healthcare provider is recommended in both situations.
A range of period blood colors is typical
Changes in the color of your period blood are often nothing to worry about. Track your bleeding with Clue to learn more about your personal patterns, and be aware of any changes in blood volume, changes in cycle length, pain, or any bleeding that doesn’t follow a pattern, as these may indicate underlying conditions.
You know your body. If you are concerned about changes to your regular menstrual cycle, contact your gynecologist or healthcare provider to discuss your concerns.
Article was originally published on Oct. 19, 2017.
