Red diarrhea is usually caused by something you ate, but it can also signal bleeding somewhere in your digestive tract. The color alone doesn’t tell you which one it is, so the key is looking at what else is going on: other symptoms, what you’ve recently eaten, and whether the red color persists.
Foods That Turn Stool Red
The most common and least concerning explanation is diet. Beets are the classic culprit. They contain a red pigment called betanin that passes through your digestive system largely intact, giving stool a blood-red appearance that can look alarming. Cherries, tomatoes, red gelatin, cranberries, and red popsicles can do the same thing. Brightly colored frostings and snacks with artificial red dyes are another frequent cause, especially in children.
If you ate any of these within the past 24 to 72 hours, that’s likely your answer. The color should clear up on its own once the food works through your system. A simple way to test: think back to your last few meals. If you had beet soup or a bag of red candy, wait a day or two and see if the color returns.
Medications That Mimic Blood
Certain medications can turn stool red or maroon without any actual bleeding. One well-documented example is cefdinir, an antibiotic commonly prescribed for ear infections. When cefdinir reacts with iron (including iron in supplements or fortified formula), it forms a compound that gives stool a striking red discoloration. This catches many people off guard, especially parents of young children on the antibiotic.
Other substances that can shift stool into the pink-to-red range include rifampin (used for tuberculosis), certain laxatives containing senna, and blackberries in large quantities. If you recently started a new medication and noticed the color change, check the side effects or call your pharmacist before assuming the worst.
Bright Red Blood in Diarrhea
If the red color isn’t from food or medication, you may be seeing actual blood. Bright red blood typically means the source is in the lower part of your digestive tract: the colon, rectum, or anus. The blood hasn’t had time to be broken down by digestion, so it stays red.
Two of the most common lower sources are hemorrhoids and anal fissures. Hemorrhoids develop from pressure or straining, and anal fissures are small tears in the lining of the anal canal, often from passing hard stool. Both can produce bright red streaks on toilet paper or in the bowl. However, these conditions are more associated with formed stool than with diarrhea. If you’re having actual loose, watery stool that’s red throughout, the source is more likely higher up in the colon.
Infections That Cause Bloody Diarrhea
Several bacterial infections can inflame and damage the lining of your intestines enough to cause bleeding. The result is diarrhea mixed with blood, often accompanied by severe stomach cramps, nausea, or fever.
- E. coli O157:H7 produces a toxin that damages the small intestine’s lining, causing bloody diarrhea and vomiting. This strain is particularly dangerous for young children because it can lead to kidney damage.
- Shigella causes intense inflammation in the colon and is a leading cause of bloody diarrhea worldwide, spreading easily through contaminated food or water.
- C. diff infections can cause hemorrhagic colitis, where the colon bleeds directly into stool. This often follows a course of antibiotics that disrupted the normal balance of gut bacteria.
Infectious bloody diarrhea tends to come on suddenly and feel distinctly different from a normal stomach bug. The cramps are more severe, and you may notice mucus or pus mixed in with the blood. Most mild-to-moderate cases don’t require specific testing, but stool cultures remain the standard way to identify the exact bacteria if your symptoms are severe or don’t improve.
Inflammatory Bowel Disease
Ulcerative colitis is one of the most common chronic causes of bloody diarrhea. It occurs when an abnormal immune response triggers ongoing inflammation in the large intestine. The hallmark symptoms are diarrhea with blood, cramping abdominal pain, and a persistent feeling that you need to have a bowel movement even when your bowel is empty.
Severity varies widely. Mild ulcerative colitis might mean fewer than four loose stools a day with occasional blood. Severe cases can involve more than six bloody bowel movements daily, along with fatigue, fever, nausea, and weight loss. In the most extreme flares, people experience more than 10 bloody bowel movements in a single day. If you’re seeing blood in your diarrhea repeatedly over weeks rather than just once, and especially if you’re also losing weight or running fevers, this is the kind of condition that needs evaluation.
Reduced Blood Flow to the Colon
In adults over 60, ischemic colitis is another possible cause. This happens when blood flow to part of the colon is temporarily reduced, damaging the tissue and causing bright red or maroon blood in the stool. Sometimes blood passes on its own without any stool at all. The condition is more common in people with heart disease, diabetes, or other vascular problems, and it typically comes with sudden cramping on one side of the abdomen.
What the Color Tells You
The shade of red matters. Bright red blood that’s clearly visible on the surface of stool or in the toilet water points to a source in the colon, rectum, or anus. But if your stool is jet black and sticky, like tar, that usually means the bleeding is happening higher up, in the stomach or upper intestine. Blood that travels through the full digestive tract gets broken down and turns dark. Very rapid bleeding from the upper tract can sometimes still appear red by the time it reaches the toilet, but this is less common and usually involves large volumes of blood.
Red diarrhea that happens once, lines up with something you ate, and doesn’t come with pain or fever is rarely something to worry about. Red diarrhea that recurs over several days, comes with cramping or fever, or involves enough blood to change the toilet water color is worth getting evaluated. For persistent cases, the standard workup typically starts with a stool sample to check for infection and may progress to a colonoscopy if an inflammatory or structural cause is suspected.