Seeing blood in your stool — or even just on toilet paper after using the toilet — may feel scary. But in most cases, it’s caused by something other than cancer, like hemorrhoids or a small tear in the digestive tract. Still, it’s your body’s way of signaling that something isn’t right, and it’s important to pay attention and get it checked by a doctor.
In this article, we walk through what you need to know, including:
- What causes blood in stool?
- How much bloody stool is worrisome?
- Bright red versus dark red blood
- When to call a doctor
If you or a loved one is concerned about possible signs or symptoms of cancer and would like an initial consultation or a second opinion, call us 24/7 at 877-460-4673.
What Causes Blood in Stool?
Blood in your stool may come from many different conditions — most of them common and treatable. In fact, it usually means there’s bleeding somewhere in the gastrointestinal (GI) tract, which includes everything from your stomach to your rectum.
Arjun Gupta, M.D., F.A.S.C.O., a medical oncologist specializing in gastrointestinal cancers at City of Hope® Cancer Center Phoenix, explains that most causes of bloody stool are benign.
“Doctors most often see things like hemorrhoids or anal fissures, which are small tears,” he says. “Constipation or straining during bowel movements can also lead to bleeding.”
Still, he says it’s important to get checked so doctors don’t miss something more serious.
Though less common, other possible causes of blood in stool include:
- Infections of the stomach or intestines (gastroenteritis)
- Inflammatory bowel disease (IBD), such as Crohn’s disease or ulcerative colitis
- Diverticulitis (inflamed pouches in the colon)
- Stomach or intestinal ulcers
- Certain medications, like blood thinners or nonsteroidal anti-inflammatory drugs (NSAIDs)
- Colon or rectal polyps (growths that may sometimes become cancer)
- Colorectal or anal cancer (less common, but important to rule out)
“The key takeaway is while blood in your stool is often caused by something minor, there’s no reliable way to tell the cause just by looking,” Dr. Gupta says. “That’s why it’s always worth a conversation with a doctor, especially if it keeps happening or comes with other symptoms.”
How Much Bloody Stool Is Worrisome?
There’s no safe amount of blood in your stool, and the amount may look quite different from person to person. In some cases, it may appear as just a small streak or spot on toilet paper. In others, it may be enough to turn the toilet water red. Both situations may happen, and neither should be ignored.
According to the American Cancer Society, even small amounts of bright red blood may come from common issues like hemorrhoids or small tears. Larger amounts — such as blood filling the toilet bowl, passing clots or ongoing bleeding — may indicate a more serious problem and need urgent care.
“I tell patients that it’s not about how much rectal bleeding you see with your eyes, it’s about the fact that it’s there,” says Dr. Gupta. “Any amount should trigger a conversation with your doctor.”
Bright Red vs. Dark Red Blood
The color of blood in your stool may offer important clues about the source of bleeding in your digestive system.
Bright red blood (hematochezia) usually means the bleeding is coming from the lower part of the GI tract, such as the rectum or anus. You might notice it as a small streak on toilet paper or on the surface of the stool. Common causes include hemorrhoids or small tears.
Dark red, maroon or black (tarry) stool (melena) typically means the bleeding is coming from the upper GI tract, such as the stomach or intestines. As the blood travels through the body, it gets digested, which makes it look darker. Darker blood is often related to iron pills or blood thinners, ulcers, inflammatory bowel disease (IBD), polyps or cancer.
When to Call a Doctor
While there isn’t a strict rule of thumb for when to call a doctor about rectal bleeding, there are clear signs that it’s time to get checked.
Call a doctor if:
- You see blood more than once or it keeps returning
- The amount seems large, for example, blood in the toilet or clots
- You’re experiencing other symptoms, like abdominal pain, fatigue or changes in bowel habits
- You have a personal or family history of colorectal cancer or polyps
- Something just doesn’t feel right
Get care immediately if:
- There’s a lot of blood in the stool or toilet
- You have ongoing or active bleeding
- You feel lightheaded, weak or short of breath
Remember, bleeding may come and go — and even small amounts shouldn’t be ignored. The only way to know the cause is to get clinically evaluated.
Dr. Gupta says: “There’s no need to panic, but don’t wait either. If you notice blood in your stool, reach out to a doctor, so we can help determine the proper next steps.”
If you or a loved one is concerned about possible signs or symptoms of cancer and would like an initial consultation or a second opinion, call us 24/7 at 877-460-4673.