Period Blood Colors Explained (What’s Normal and What’s Not)

Women know that all menstrual bleeding is not the same. The amount of bleeding, whether or not there are clots, and whether or not you have cramping can change during a single menstrual cycle or between menstrual cycles. One thing you may not have considered, however, is what your menstrual blood color could mean. At Diana Health, we receive questions on all kinds of topics, and we’re here to empower you with the knowledge you need to confidently navigate everyday experiences—like understanding the ins and outs of your menstrual cycle.

Blood is composed of red blood cells (erythrocytes), white blood cells (leukocytes), and blood plasma that appears yellowish. To understand why blood appears to be different colors, it’s essential to understand some basic chemistry first. The color change of blood happens because of changes in the chemical state of hemoglobin, the protein in the red blood cells that transports oxygen. As the amount of oxygenation shifts and the longer the hemoglobin has had time to react with oxygen, the tone of the blood shifts. Also, as blood dries out, it darkens. Now that you’ve passed your science test, let’s take a look at the different colors your menstrual blood can be and what it means:

1. Darker red or purplish: Blood that is deoxygenated appears darker red. Without oxygen, the hemoglobin absorbs and reflects light differently. This is why when blood is drawn for blood work, it is dark red or may even appear to be reddish-purple in color. Blood that has not had time to be exposed to sufficient oxygen to become brighter red, may still appear darker red or purplish. 
2. Bright red: When hemoglobin is oxygenated, oxygen is bound to the iron in hemoglobin. When oxygen and iron bind, the shape and light-absorbing properties of hemoglobin change, leading to the oxygenated blood appearing bright red. When there is active bleeding, the blood is recently exposed to air, and becomes newly oxygenated, it appears bright red. This oxygenation happens more quickly when there is a smaller amount of blood. Blood may appear bright red when there is a small amount of spotting with new blood or when there is very active flow. Red blood is fresh blood.   
3. Brownish, rust, or very dark brown: When blood dries or is stored for prolonged periods of time, it may become brown, rust, or even blackish in color. With exposure to air, the blood starts to dry and the color eventually shifts from bright red to brown. This is similar to what happens when iron is exposed to oxygen and rusts over time. Also, as the moisture evaporates, the color becomes more intense and darker due to the absence of liquid. This is why dry menstrual blood often appears brownish or rust in color. This color blood may be more common at the beginning or end of menstruation, when blood has taken longer to exit the body, or when blood has had time to dry.   
4. Pink blood: When bright red or dark red blood is diluted with white or clear vaginal or cervical secretions, it may appear lighter or pink. When a woman has lighter bleeding or spotting, she is more likely to have blood that appears pink since the blood-to-clear or white secretions ratio is lower. 
5. White, clear, or yellow: This actually is not blood. Instead, it is a vaginal discharge or secretions that are usually completely normal at various times in a reproductive-age woman’s cycle. Vaginal discharge changes in color, consistency, and amount throughout a woman’s cycle.
6. Grey, green, or yellow: This color discharge may indicate that there is an infection or an overgrowth of “bad” bacteria in the vagina. 

Although your menstrual blood or discharge might be different at different times of your cycle, there are times when you should seek medical care. For example, a fever, pain, and/or abnormal odor along with any bleeding or vaginal discharge may indicate an infection. If you have very heavy bleeding (regardless of color), you may need emergent care. See this blog for more information on irregular bleeding and blood clots. If you are pregnant and have any bleeding or abnormal vaginal discharge, you should let your healthcare provider know and seek care right away. Also, women who have gone through menopause and have any bleeding should reach out for evaluation. 

Usually variation in menstrual blood color is not cause for concern. However, you are always welcome to reach out to our women’s health experts at Diana Health to discuss any aspect of your menstrual cycle or bleeding. Send us a message using the Diana Health app, or book a visit online to see a provider.