Dark brown period blood: Everything you need to know

Crimson, scarlet, cherry red — there are only so many ways you can describe the color of blood, right? Not so when it comes to your period. If you often get curious about the contents of your menstrual cup, pad, or tampon, you might have noticed a range of different colors. You may even notice that at certain times, your period blood is dark brown. But is that normal? 

The color of period blood can differ from person to person — and even cycle to cycle. That means your personal period color palette may change from one month to the next. While you might not have been expecting to see dark brown blood during your period, it’s pretty easily explained. 

So here’s the lowdown on dark brown period blood — from what makes it that color to when to speak to your doctor. 

Key takeaways

• Brown isn’t a color you’d usually associate with blood, but there’s a reason your period may not be red. 
• Old blood becomes darker the longer it stays outside of blood vessels. When it comes into contact with oxygen in the air, a process called “oxidation” occurs, which turns it brown (or so dark it looks almost black).
• If you regularly get brown blood at the beginning and end of your period, this is typically nothing to worry about. However, spotting or brown period blood that occurs mid-cycle may be a sign that something isn’t right.  
• It’s always a good idea to speak to your health care provider if you notice any changes with your period. 

Why does my period color change during a period? 

We normally think of blood as a bright berry red; your period is no exception. However, there’s a spectrum of colors your period might be, from red to pink and brown. To figure out why your period blood might change color, it can be helpful to understand why it’s red in the first place. 

If you’ve ever cut yourself, you’ll notice that you’ll likely bleed bright red blood. This is because of something called hemoglobin, which is found in your red blood cells. Hemoglobin molecules carry oxygen around the body to make sure our cells and tissues are working effectively, but they also carry a protein called heme, which contains iron. When the iron in hemoglobin picks up oxygen in the lungs, it turns red. 

So what does brown period blood mean? Obstetrician and gynecologist at Georgia Obstetrics and Gynecology, Georgia, US, Dr. Renita White explains, “Blood that is older has been oxidized, meaning it has reacted with oxygen. This oxidation leads to red blood turning a browner color.” 

When you think about what your period looks like, you might notice that it goes from light to bright to dark. Yours might look like the following: 

• Beginning: At the very start of your period, it might appear pink. As you start your period, it can mix in with vaginal discharge, so the bright red blood can become diluted. After some time, it may appear red as a ruby. This is an indication that your period is probably at its heaviest. As a general rule, the redder the blood, the faster your flow. During the first few days of your period, the lining of your uterus sheds quickly as chemicals called prostaglandins tell muscles and blood vessels there to contract. That’s what causes those annoying cramps some of us get.
• Midpoint: Once the first couple of days of your period are over, you might notice a color change. That bright strawberry red from the beginning of your cycle can turn a darker, scarlet color as your period progresses. Darker period blood means it’s been in your body longer, giving it more time to react with oxygen. It also suggests that your flow has slowed down a little bit.
• End: You might experience dark brown period blood toward the end of your cycle as your period blood has had more time outside of your blood vessels — and your flow slows down even more. This means blood is leaving your uterus at a slower pace, giving your blood more time to react with oxygen in your body (oxidation). 

Why do I have brown blood on the first day of my period? 

Your period and cycle are pretty personal to you. It might change from month to month or even throughout your life. The first day of your period might be your heaviest and the point when you notice the reddest blood. Alternatively, your flow may be slower at the start of your period, which may be why you notice darker or brown blood. 

“A lighter flow gives blood time to be oxidized, which can lead to brown blood,” explains Dr. White. Dark brown blood can also occur at the end of a period when, as we explained previously, blood has been in the vagina for longer and has more of a chance to be oxidized.

Additional causes of brown period blood 

Brown period blood is fairly common and isn’t typically something to worry about on its own. However, if you notice it alongside other symptoms, it may indicate that something else is going on. This could include:

Pregnancy 

Brown period blood isn’t a pregnancy symptom; however, spotting or light bleeding could be a sign of early pregnancy. Confused? Let’s break this down. 

Every cycle, one of your ovaries releases an egg to be potentially fertilized by a sperm. This is called ovulation. If it is fertilized, then it starts the journey down one of your uterine tubes to eventually attach to the lining of your uterus. This is called implantation. 

Around this time, some people report light bleeding or pink bloody discharge, which is known as implantation bleeding. However, it’s impossible to know when implantation has taken place, and differentiating between implantation bleeding and the start of your period can be really tough. 

If your period is lighter than normal, and you think you might be pregnant, the best thing to do is wait until the first day of a missed period and then take an at-home pregnancy test. Beyond that, Dr. White suggests, “If you have a positive pregnancy test, and you’re having bleeding of any kind, talk to your health care provider.”

Perimenopause 

Perimenopause is the term used to describe the transition toward menopause (when you haven’t had a period for 12 months). Your cycle doesn’t just stop overnight, and perimenopause can last around four to eight years. While everyone is different, most of us will experience perimenopause in our 40s, but it can start anytime between our late 30s and 50s.

Perimenopause is a time of major hormonal changes as the amount of estrogen that’s produced by your ovaries begins to fluctuate. Dr. White explains that because of this, “there can be changes in your monthly cycle that lead to moments of irregular bleeding or brown spotting.” Perimenopause is also associated with other symptoms, such as: 

• Mood changes
• Night sweats
• Trouble sleeping
• Vaginal dryness

If you have brown spotting, that doesn’t automatically mean that you’re perimenopausal. However, “If you have irregular brown spotting and you’re over the age of 40, your health care provider may talk to you about the possibility of perimenopause,” says Dr. White. So be sure to schedule an appointment if that sounds like you.

Endometriosis 

Endometriosis (or “endo,” as it’s sometimes called) is a condition where tissue similar to the lining of your uterus grows in other parts of your body, such as your abdomen and/or pelvic area. This tissue behaves in the same way that the lining of your uterus does, which means that throughout your cycle, it builds up and then breaks down and falls away. 

When this happens in your uterus, the tissue leaves your body in the form of your period. However, when the tissue builds up in other parts of your body, it has no way of leaving it. This means that endometriosis tissue can swell, causing inflammation, and scar tissue can develop.

“Endometriosis is typically characterized by painful menstrual cycles and pelvic pain,” explains Dr. White. You might also experience pain during sex and spotting between your periods, which may be brown. If you’re having brown spotting between periods, it’s best to speak to your health care provider so they can do some tests.

Sexually transmitted infections (STIs) 

If your period blood is brown, it may be worth doing an STI screening test. As Dr. White explains, “Some STIs, like gonorrhea, chlamydia, and trichomoniasis, can cause light irregular bleeding. The blood can be brown due to the light nature of bleeding.”

Doing an STI test might sound daunting, but they’re very quick, and most infections are easily treatable. Remember, if left untreated, STIs like gonorrhea, chlamydia, and trichomoniasis can cause further complications, and your symptoms may worsen. So, it’s always best to get checked. 

Uterine fibroids 

You might not have heard of uterine fibroids, but 70% of women end up having fibroids by the age of 50 — and they can be a potential cause of dark brown period blood.

Fibroids are growths that form inside your uterus, but, rest assured, they’re noncancerous and usually nothing to worry about. They can vary in size. Some are the size of a lentil (or too small for the eye to see), while others can be the size of a melon. You can have one or several (like a bunch of grapes). Unless they cause symptoms, most of us never know we have them.

Why are they so common? It appears that levels of your reproductive hormones — estrogen and progesterone — could play a role, although researchers still aren’t entirely sure what causes fibroids. While the exact cause is still unclear, some researchers believe there could also be genetic reasons. 

As we’ve learned, fibroids are often asymptomatic (don’t cause symptoms), but if you do notice any of these symptoms, then it’s best to get checked out by your health care provider:

• Heavy or painful periods
• Lower back or abdominal pain
• A feeling of pressure in your pelvic area
• Constipation
• Pain during sex
• An increased need to pee

As Dr. White explains, light brown spotting is also a symptom: “Depending on the location of fibroids, light irregular brown bleeding is possible. Fibroids located in the uterine cavity are more likely to cause [this].” While some fibroids can cause heavier bleeding, if you have brown period blood or spotting alongside any of the symptoms listed above, speak to your health care provider.

Hormonal birth control 

If you’ve started taking a new form of hormonal birth control, like the pill, patches, injections, or an intrauterine device, you may have seen a change in the color of your period blood. While this might not be a symptom you expected, it’s fairly easily explained. 

As the name would suggest, hormonal birth control contains a dose of the hormones estrogen and/or progestin (some birth control contains both, while others contain only one). It can take your body a few cycles to get used to a change in your hormone levels. This means that you might experience brown blood spotting, sometimes called breakthrough bleeding. 

“Hormonal birth control can lighten a period so much that it can cause brown bleeding,” says Dr. White. If you have just started a new method of birth control and notice a change in your period, then it can still be good to check it out with your health care provider. 

When to see your doctor and what to say 

Generally speaking, if you notice brown blood at the beginning or end of your period, it probably isn’t a cause for concern. “There is no need to worry if you have brown bleeding each month if your cycle is usually predictable,” Dr. White explains. 

“If you’re having brown blood rather than a full normal period, this could indicate that you are not ovulating and having a menstrual cycle,” she adds. “If you are having irregular bleeding (whether it is brown or red) instead of a regular monthly cycle, you should talk to your doctor right away.” 

It’s normal for your cycle to change slightly throughout your life, but if it becomes erratic, it’s best to speak to a doctor who can investigate further.