Why Is There Blood In My Stool During My Period?

Finding blood in your stool during your period is common, and it usually has a simple explanation. The most frequent cause is that menstrual blood from your vagina mixes with stool as it leaves your body, so the blood you see on toilet paper or in the bowl may not be coming from your intestines at all. Other causes include endometriosis affecting the bowel, hemorrhoids, and ordinary digestive problems that have nothing to do with your cycle. Because rectal bleeding can also signal a condition that needs treatment, the pattern and appearance of the blood matter.

Why Is There Blood In My Stool During My Period?

Blood shows up for one of two broad reasons: it came from your vagina and got mixed with stool, or it came from somewhere in your digestive tract and happened to appear while you were menstruating.

The first reason is far more common. Menstrual flow exits through the vagina, which sits very close to the anus. When you pass stool, blood that is already on the skin or in the area can end up on the toilet paper or in the water. This is not rectal bleeding. It is simple proximity and gravity.

The second reason involves actual bleeding from the rectum or lower bowel. That blood can be bright red, dark red, or nearly black depending on how far up the digestive tract it started. Bright red blood usually points to a source close to the exit, such as the anus or rectum. Darker blood suggests a source higher up.

There is a third possibility that connects the two: a condition where tissue similar to the lining of the uterus grows outside the uterus. When that tissue attaches to the bowel, it can bleed in response to the same hormonal signals that trigger a period. This is called bowel endometriosis, and it is less common than simple menstrual contamination but well documented.

How Can You Tell If The Blood Is From Your Period Or Your Bowel?

Where the blood appears gives you the clearest clue. Blood that comes from your period tends to show up on toilet paper when you wipe from front to back, or it appears as streaks on the outside of the stool rather than mixed through it.

Blood from the bowel usually behaves differently. It may be mixed into the stool, coat the surface, drip into the bowl after a bowel movement, or appear on its own separate from stool. Bright red blood that drips or streaks is often from a source near the anus. Blood that is dark, tarry, or mixed throughout the stool suggests a source higher in the digestive tract.

Timing also helps. If the blood only appears during your period and never at other times of the month, menstrual contamination or a hormone-sensitive condition becomes more likely. If you see blood at other points in your cycle too, the cause is probably not related to your period.

One useful step is to check before you wipe. Look at the stool in the bowl first, then wipe. If the blood is only on the paper after wiping from front to back, it more likely came from the vaginal area. If it is already in the bowl or on the stool, it more likely came from the rectum.

What Causes Rectal Bleeding That Coincides With Periods?

Several conditions can cause rectal bleeding that happens to overlap with your period. Some are related to hormones and some are not.

• Hemorrhoids are swollen veins in the anus and lower rectum. They are a very common cause of bright red blood on toilet paper. Hormonal changes and the pressure of a bowel movement can make them bleed more easily.
• Anal fissures are small tears in the lining of the anus, often from passing hard stool. They cause sharp pain and bright red blood.
• Bowel endometriosis occurs when tissue like the uterine lining grows on or near the bowel. It can cause bleeding from the rectum during periods, along with pain with bowel movements and cyclical cramping.
• Inflammatory bowel disease, including ulcerative colitis and Crohn’s disease, can cause blood in the stool. Symptoms often fluctuate and may not follow a menstrual pattern.
• Diverticular bleeding happens when small pouches in the colon wall bleed. It is more common in older adults.
• Colorectal polyps or cancer can bleed, sometimes without other symptoms. This is why any persistent rectal bleeding deserves a medical evaluation.

Some of these conditions are common and manageable. Others need prompt attention. The only way to know which one applies to you is to have a clinician evaluate the bleeding.

Could Endometriosis Be Causing Blood In My Stool?

Endometriosis can affect the bowel, and when it does, it can cause bleeding from the rectum during your period. This happens because the misplaced tissue responds to the same hormones that control your menstrual cycle. When hormone levels drop before a period, that tissue can shed and bleed, just like the lining of the uterus.

Bowel endometriosis is not the same as having endometrial tissue on the outside of the bowel. It means the tissue has grown into the bowel wall itself. This is less common than other forms of endometriosis, and it is often diagnosed later because symptoms overlap with other digestive problems.

Signs that point toward bowel endometriosis include:

• Rectal bleeding that happens mainly or only around your period
• Pain with bowel movements during your period
• Cyclical cramping or pelvic pain that worsens before and during menstruation
• Bloating, diarrhea, or constipation that follows your cycle
• Pain during sex, especially with deep penetration

Endometriosis is diagnosed through a combination of symptoms, imaging, and sometimes surgery. No blood test can confirm it. If your symptoms follow a clear monthly pattern, that is worth mentioning to your doctor.

When Should You See A Doctor About Blood In Your Stool?

Any rectal bleeding that is new, persistent, or unexplained should be evaluated by a clinician. That is the standard position across medical organizations, and it applies whether or not you are on your period.

Seek medical care promptly if you notice:

• Blood that is dark, tarry, or black
• Large amounts of blood in the toilet bowl
• Blood mixed throughout the stool rather than just on the surface
• Bleeding that continues after your period ends
• Bleeding along with dizziness, weakness, or a racing heart
• Unexplained weight loss or a change in bowel habits that lasts more than a few weeks
• A family history of colorectal cancer or inflammatory bowel disease

Bright red blood on toilet paper is often from a minor cause like a hemorrhoid or a small fissure. But you cannot tell the difference between a minor cause and a serious one just by looking. A doctor can examine you, ask about your history, and decide whether testing is needed.

Do not wait for your next period to see if it happens again. If you have already seen blood, that is enough reason to get checked.

How Do Doctors Figure Out The Cause?

Doctors start with your history and a physical exam. They will ask about the timing of the bleeding, its color, whether it is mixed with stool, and whether it happens outside your period. They may also ask about pain, bowel habits, and family history.

Depending on what they find, they may recommend:

• A rectal exam to check for hemorrhoids, fissures, or masses
• Blood tests to check for anemia or signs of inflammation
• A stool test to look for hidden blood or infection
• A colonoscopy to examine the inside of the colon and rectum
• Imaging such as ultrasound or MRI if endometriosis is suspected

Colonoscopy is the most direct way to see what is happening inside the colon. It allows a doctor to find polyps, inflammation, or other sources of bleeding and to take tissue samples if needed. For people with symptoms that could be from endometriosis, imaging and sometimes laparoscopy may be part of the workup.

The right tests depend on your age, symptoms, and risk factors. There is no single test that covers every possible cause.

What Does The Color Of The Blood Tell You?

The color of blood in your stool gives a rough clue about where it came from. It is not a diagnosis, but it helps guide what to look for.

Bright red blood is the most common type seen with hemorrhoids and fissures. Black, tarry stool is less common and needs prompt medical attention. Dark red blood falls somewhere in between and also warrants a check.

Color alone cannot tell you whether the blood is from your period or your bowel. If the blood is bright red and only appears on toilet paper when you wipe from front to back, menstrual contamination is a reasonable first thought. If it is mixed with stool or appears in the bowl, the source is more likely the bowel.