Red stool is usually caused by something you ate, not something dangerous. Beets, red gelatin, tomato soup, red-dyed snacks, and fruit punch are the most common culprits. But if you haven’t eaten anything red recently, the color could be blood, and that’s worth paying attention to.
The key distinction is whether the red comes from food or from bleeding somewhere in your digestive tract. Here’s how to figure out which situation you’re in and what to do about it.
Foods and Medications That Turn Stool Red
Beets are the most well-known cause of red or dark-red stool. The pigment in beetroot is strong enough to discolor both urine and stool, sometimes dramatically. If you ate beets, beet juice, or beet-based snacks in the last day or two, that’s very likely your answer. The discoloration typically clears within one to two bowel movements after the beets pass through your system.
Other common foods that can make stool look red or reddish include tomato sauce, red peppers, cranberries, red velvet cake, and anything with red food dye (like popsicles, candy, or colored cereal). Even large amounts of watermelon or red Gatorade can do it.
Certain medications also cause red stool. One notable example is a common antibiotic (cefdinir), which reacts with iron in the gut to form a reddish precipitate. If you’re taking an antibiotic and an iron supplement at the same time, this combination can produce stool that looks alarmingly red or rust-colored but is completely harmless.
Bright Red Blood: Hemorrhoids and Fissures
If the red you’re seeing is clearly blood, the most common sources are hemorrhoids and anal fissures. These are both extremely common and rarely dangerous, though they can be uncomfortable.
With internal hemorrhoids, you often won’t feel any pain at all. The only sign may be bright red blood on the toilet paper, streaked on the surface of your stool, or dripping into the bowl after you finish. External hemorrhoids, on the other hand, can cause a noticeable lump near the anus along with itching and soreness.
Anal fissures are small tears in the lining of the anus, usually caused by passing hard stool. They tend to cause a sharp, stinging pain during the bowel movement itself, sometimes followed by a throbbing ache that can last for hours. You’ll typically see blood on the toilet paper or on the surface of the stool, similar to hemorrhoids, but the pain is the distinguishing feature.
Both conditions generally improve with softer stools (more fiber, more water) and time. If bleeding is mild and you can connect it to straining or constipation, this is the most likely explanation.
What the Color of Blood Tells You
The shade of red matters because it points to where in the digestive tract the bleeding originates. Bright red blood almost always comes from the lower part of the tract: the colon, rectum, or anus. The blood hasn’t had time to be broken down, so it looks fresh.
Dark red or maroon-colored blood suggests bleeding from higher up in the colon. Black, tarry stool (which may not look “red” at all) usually means the bleeding source is in the stomach or upper intestine. Blood that travels through the full length of the gut gets digested along the way, turning it dark and sticky.
There’s one exception: very rapid, heavy bleeding from the upper gut can move through fast enough to still appear red by the time it exits. But this would come with other obvious signs like feeling faint or weak.
Less Common but More Serious Causes
Diverticular bleeding happens when small pouches in the colon wall (diverticula) rupture a blood vessel. It’s painless, which can make it surprising. The hallmark is a sudden, large volume of blood in the toilet, often dark red or maroon. Less than 5% of people with diverticula ever experience this, and it’s more common after age 60. Most episodes stop on their own, but the volume of blood can be significant enough to need medical evaluation.
Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, can cause blood in the stool along with other persistent symptoms: abdominal cramping, diarrhea that won’t resolve, unintentional weight loss, and fatigue. If bloody stool is accompanied by weeks of digestive symptoms, IBD is one possibility worth investigating.
Bacterial infections from contaminated food or water can also cause bloody diarrhea. Most of these resolve on their own within a few days, but if you’ve been sick with bloody diarrhea for more than two days, it’s worth calling a provider.
Colorectal Cancer Warning Signs
Colon or rectal cancer can cause blood in the stool, but it almost always comes with other changes that develop over weeks or months. Warning signs to watch for include stool that becomes persistently thin or ribbon-shaped, ongoing constipation or diarrhea lasting more than a few days, a feeling that you can’t fully empty your bowels, and unexplained weight loss. Early colon cancer sometimes causes no symptoms at all, which is why routine screening matters. A one-time episode of red stool without other symptoms is unlikely to be cancer, but recurrent or persistent blood deserves a workup.
How Doctors Test for Hidden Blood
If the cause isn’t obvious, your provider may order a stool test to check for blood that isn’t visible to the naked eye. There are two main types. The older version (guaiac test) detects a component of blood but can give false positives if you’ve recently eaten red meat or certain raw vegetables, and false negatives if you’ve taken vitamin C. The newer version (fecal immunochemical test, or FIT) specifically detects human blood proteins and isn’t affected by diet, making it more accurate. In head-to-head comparisons, FIT detected nearly twice as many cancers as the older test. FIT is also selective for bleeding in the colon and rectum, which is usually the area of concern.
When Red Stool Needs Urgent Attention
Most causes of red stool are benign, but certain combinations of symptoms signal something that needs prompt evaluation. Seek care right away if you’re passing large blood clots, if bleeding is heavy or doesn’t stop, or if your stool is black and tarry. Feeling lightheaded, dizzy, or like you might faint alongside bloody stool is a sign of significant blood loss and warrants emergency care. A sudden drop in blood pressure from GI bleeding can happen when roughly 15% or more of your blood volume has been lost.
For milder, intermittent bleeding without those alarm signs, it’s still a good idea to get it checked. Even painless, low-volume rectal bleeding that’s been going on for a while can indicate a condition that benefits from treatment. The first step is usually a conversation with your primary care provider, who can determine whether you need further testing based on your age, symptoms, and history.