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Why is my period blood brown?

Written by:, PhD, Founder and Inventor of the Proov test — the first and only FDA-cleared test to confirm successful ovulation at home.

why is my period blood brown

If you’ve ever paid attention to your menstrual flow, you may have noticed a lot of variety! The menstrual flow isn’t just made up of blood (although that makes up a lot of it!), but includes vaginal secretions like cervical mucus and endometrial fluid, tissue from the uterine lining, and more. There can also be a variety of colors involved in menstruation: bright red, pink, dark red, and brown/black.

Most of us expect to see some shade of red when on our periods, as this is a sign of active bleeding. But when the color gets darker and we start seeing brown, questions can pop up! Am I having a brown period? What’s causing this? Is it normal? Should I talk with my doctor about what I’m seeing?

This blog is here to help answer those questions and calm those fears!

Is brown period blood normal?

First things first, it can be completely normal to observe brown discharge as a part of the period flow.  Yes, brown spotting is likely nothing to worry about! Especially if it’s not accompanied by other symptoms like severe cramps, sharp abdominal pain, or headaches/nausea, brown blood is likely a normal part of your menstrual cycle or an expected response to hormonal changes.

Although there are lots of possible causes of brown spotting, we’re going to discuss some of the most common causes. Do any apply to you?

What causes a brown period?

why is my period blood brown

You’re at the Beginning or End of Your Flow

The most common cause for observing brown discharge is that you are at the beginning or the end of your menstrual flow. Have you ever heard the term “old blood” when talking about brown bleeding? This is because blood that’s exposed to oxygen changes color. Blood still in the veins or the body is a deep red, but as this blood is exposed to oxygen, it begins changing color. So the longer blood is exposed to this oxygen, it can begin to look more and more brown in color. 

Since it’s not unusual for a period to begin with a day or two of spotting, or end in the same way, then this blood may have a brown coloring to it.

You’re on Birth Control

When someone is on hormonal contraception (also known as birth control), they receive a low dose of artificial hormones each day. These mimic the reproductive hormones estrogen or progesterone, or both. These artificial hormones are replicated in both an oral contraceptive (meaning, birth control pills) and a hormonal IUD. This process can cause some unusual bleeding that may be red or brown. This is sometimes referred to as breakthrough bleeding.

If using an oral form of hormonal contraception, the body will have a withdrawal bleed when the placebo pills are taken. Although this is not a technical menstrual flow, the bleeding can vary in how heavy it is and what color the blood is. 

So your brown bleeding may be in response to your specific hormonal contraception.

You May Have PCOS

As we’ve established, the uterine lining can experience light bleeding for a variety of reasons. When the body experiences shifts in reproductive hormones, the uterine lining will respond to these changes. Sometimes this response comes in the form of spotting, which can be red when active, or brown when the active bleeding has stopped.

For those with PCOS, reproductive hormones may rise and fall in a non-traditional pattern, causing irregular cycles or missed periods, acne, weight gain, or unusual spotting. This light spotting is not a menstrual period, even if it comes when a menstrual period is expected.

You Could be Experiencing Perimenopause

Perimenopause is the stage in which the body is transitioning from active reproductive hormone production and menstrual cycles to menopause. This will begin at a different age for every woman (from the mid-30s to even in the 50s), but the most common time for this to begin is the mid-40s. 

Being perimenopausal is not the same thing as being menopausal. Menopause officially occurs one year after a woman’s final menstrual flow. Perimenopause (the entire time of transition from the first symptom of hormonal changes to the last menstrual period) can last for several years, anywhere from 7 to 14!. Common symptoms during perimenopause are spotting outside of a period (which can be brown), heavy bleeding, more frequent periods, long periods of more than 7 days, hot flashes, or night sweats.

When should I see my doctor about brown period blood?

why is my period blood brown

Remember, these are just a few common reasons you could experience brown bleeding. There are many other causes, as well.  If you have any other accompanying symptoms, or are concerned about the presence or amount of brown bleeding, the best thing to do is share your concerns with your doctor. They can assess for other, less common causes of brown bleeding, like uterine polyps, fibroids, infection, or STIs.

If your brown bleeding is accompanied by heavy bleeding (soaking a pad or tampon every hour), you haven’t had a period for more than 3 months, or you think you could be pregnant, it’s not a bad idea to schedule an appointment with your doctor.

Brown bleeding can be a very normal part of menstruation. With changing reproductive hormones and a responsive uterine lining, there can be many causes of brown spotting that do not need to cause concern.

If you’re curious about your unique hormone levels, check out some of our at-home hormone tests!


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