The blood that you see during your period is similar to but not exactly the same type of blood that you see when you cut your finger. What you see on your pad or tampon or in the toilet bowl is a mixture of both blood and tissue from the lining of your uterus. How much of each, along with other factors, will influence what your period blood looks like. Period blood is also known as menstrual blood or menses. It's appearance varies from day to day during your period, across different cycles, and across different women.
What Causes Menstrual Bleeding
The menstrual cycle is controlled by hormones. These hormones regulate when and if your ovaries produce eggs. They also regulate the thickening of the lining of your uterus, also known as the endometrium. Then, your period starts when hormonal changes cause the endometrium to start to break down and separate from the wall of your uterus.1 The excess blood and tissue flow down through your cervix and out through your vagina. This mixture of blood and tissue is what makes up your menstrual flow or period blood. .
The fact that menstrual blood contains cells from the lining of the uterus is only one of the things that makes it different from the blood that you see when you cut your finger. Another, very important, difference, is the way that the blood clots -- or becomes solid. If you are healthy, when you cut your finger, your finger only until your body responds by releasing substances called clotting factors that stop the bleeding. This usually happens relatively quickly.
During your period, blood will flow from the small blood vessels that were torn when the lining of the uterus separated. This bleeding will continue until clotting factors and hormone changes stop the bleeding and restart building up the uterine lining again. However, you won't usually see blood clots the way that you do on a cut or other injury. Blood clots during your period can happen, but visible clots are often as sign that something else is going on in your body beyond your regular menstrual cycle. In fact, visible clots that are large than one inch in diameter are one way that doctors diagnose heavy menstrual bleeding, or menorrhagia.
Your menstrual blood may be thin and watery or thick and sticky. Thin and watery discharge is usually pinkish while thick and sticky discharge is usually brownish. These changes are common at the end of your cycle after most of the endometrial tissue has passed. These changes can also suggest a decreased build up in the lining of your uterus which is common as a woman approaches menopause or if her cycles are light due to other hormonal causes like stress or excessive exercise.
Understanding Period Blood Appearance
What your period blood looks like can vary a lot from cycle to cycle. It can also vary from day to day during the same cycle, and those variations are a window to what is going on inside your body. Menstrual blood can be described in a number of ways. It's useful to think about not just how much you are bleeding but the color of the blood and the consistency of the flow.
Bright Red Period Blood
The brighter red the blood the more recent the bleeding and the quicker the blood is passing through the cervix and into the vagina. Bright red blood is most likely to be present at the start of your period. You may also see brighter blood at times when you have cramps. That's because cramps occur when the uterus contracts, which may also lead to heavier blood flow.
Dark Red Period Blood
The darker the flow, ranging from dark red to brown or black, suggests slightly older blood or slower flow. For most women, their period blood gets darker over the course of their cycle. This is because older blood gets released as the deeper parts of the uterine lining get shed and the bleeding slows. Typically the color of menstrual blood is a shade or two darker than ‘normal’ bleeding. But you can see this darkening of older blood in other ways as well. You may have noticed this if you've ever gotten period blood on your clothing and waited for it to dry.
Pink Period Blood
Some people may notice that their period blood is very pink during some points of their menstrual cycle. This is usually the most common at the very beginning or end of their period, when they're bleeding very lightly. Pink period blood is nothing to worry about. It's usually just blood that has been diluted by mucus.
Extra Thick Period Blood
The consistency of your menstrual flow is in part an indication of how much endometrium or uterine lining is mixed with the blood. Typically, menstrual blood is a little thicker than ‘normal’ bleeding because of the tissue it contains.If you see large lumps, or clots, in your period blood, that may be a sign that you have fibroids. Fibroids are abnormal growths of the uterine wall. Although not cancerous, they can cause significant discomfort and heavy bleeding in some women. Large blood clots can also be the sign of a miscarriage or an ectopic pregnancy. If you experience unusual menstrual bleeding or clotting, it's not a bad idea to discuss it with your doctor.
Floods of Period Blood
Different women have different amounts of period blood, and amounts of period blood also vary across the menstrual cycle. It's normal for some women to have very light blood flow throughout their periods while others have extremely heavy blood flow. However, if you are bleeding so much and so quickly that you are regularly flooding your menstrual products and/or need to change them more than once an hour, talk to your doctor. Extremely heavy, fast menstrual bleeding may be a sign of an underlying bleeding disorder.1 This is particularly true if you have any family history of a bleeding disorder or have ever been treated for anemia.
A Word from Verywell
Around the world, up to a quarter of reproductive age women experience some type of abnormal uterine bleeding.2 Abnormal uterine bleeding takes on a variety of forms including periods that:
- are too close together or far apart
- are much heavier than would be otherwise expected
- last for longer or shorter than what's considered to be a normal range
For many such women, there are interventions that can help. Addressing the underlying causes of abnormal uterine bleeding can make a big difference in their lives. For some people, it's the different between being successful at work or school, and not being able to function.
However, it's also important to know that periods come in a wide range of normal. How wide a range? Doctors consider the following things to all be normal:2
- having a menstrual cycle that lasts anywhere from 24-38 days
- having a cycle length that varies as much as 20 days over the course of the year
- bleeding for anywhere from four and a half to eight days at a time
- losing anywhere from 5 ml - 80 ml of blood over the course of your period
There's also the question of what's normal for you, which may be different than what's normal on a population scale. Some menstrual blood is thick, some is thin. Some is pink, some is black. Some people can use only one or two pads or menstrual cups over the course of a day, others need to change them every couple of hours. Some people have no cramps, others regularly employ a hot bad or pain killers. Paying attention to the appearance of your period blood, and what your menstrual cycle feels like, is a great way to figure out what's normal for you. Tracking your period - on paper or with an app - helps you realize if something is different than usual that might make you want to seek care.
There are a number of medical conditions where changes in your menstrual bleeding can be a symptom. Not all of them are serious or need medical attention. However, signs that you should see a doctor about your period include:
- not bleeding for more than 3 months, when you know you're not pregnant
- a change from regular to irregular periods (just having a lifetime of irregular periods isn't a concern)
- bleeding for more than 7 days at a time or between periods
- bleeding so heavily that you soak through pads or tampons in only an hour or two
- severe pain during your period
- getting a fever and feeling unwell after using a tampon - this could be a sign of toxic shock4
Tracking your period can also help you realize if your normal is something that needs to change - even if it's not an emergency or even an urgency. It may be normal for you to be regularly disabled by heavy periods or painful cramps, but it shouldn't have to be. Therefore, if it's appropriate, let the data you've collected through tracking your period inspire you to talk to your doctor. Another bonus of period tracking? It gives you all the information you need to have a good discussion about your care.