Stool color is typically brown, resulting from the complex breakdown of old red blood cells. The liver produces bile, a yellowish-green fluid containing bilirubin, which aids in digestion as it travels to the intestines. Gut bacteria convert bilirubin into a pigment called stercobilin, which provides the characteristic brown hue. When stool deviates from this norm, it signals a variation in diet, digestion speed, or, less frequently, an underlying health condition.
Dietary Sources of Color Change
The most frequent and harmless cause of orange or reddish stool is the food and drink consumed within the past 72 hours. Orange coloration often stems from large quantities of beta-carotene, an organic pigment found in many plant-based foods. Eating excessive amounts of carrots, sweet potatoes, squash, or certain leafy greens can lead to a noticeable orange tint. This occurs because the body does not fully process the high concentration of carotenoid pigments as they pass through the digestive system.
Reddish discoloration is commonly caused by foods containing strong natural pigments or artificial dyes. Consuming beets is a well-known cause of reddish stool, sometimes described as beeturia, due to betacyanin pigments that resist breakdown. Similarly, highly pigmented items like red gelatin, tomato soup, cranberry juice, or products containing red food coloring can temporarily turn stool a bright red or pinkish-red color.
Certain medications can also alter stool color. The antibiotic rifampin and some antacids containing aluminum hydroxide may cause stool to appear orange. High doses of medications containing bismuth subsalicylate, like some antidiarrheal remedies, can lead to a dark, almost black appearance. If the color change is solely due to diet or medication, the stool color typically returns to brown within a day or two after the substance is cleared from the body.
Transit Time and Bile Flow
The speed at which waste moves through the intestines, known as transit time, significantly impacts the final color of the stool. If material passes through the colon too quickly, often due to diarrhea, bile pigments do not have sufficient time for complete metabolism. This rapid transit can result in a lighter, sometimes yellowish-orange or green stool, because the bile has not been fully converted to the brown stercobilin pigment.
A different mechanism involves the flow of bile, which is essential for normal brown stool color. If bile flow is obstructed or reduced, the stool will lack the necessary pigment. Conditions affecting the liver, gallbladder, or bile ducts—such as gallstones or liver disease—can cause the stool to become pale, clay-colored, or a very light, desaturated orange due to a lack of bilirubin. This paleness signals a problem with the digestive system’s pigment supply rather than a simple dietary effect.
Identifying Blood in Stool
When reddish color is not due to food, the concern shifts to the presence of blood, which can originate anywhere in the gastrointestinal tract. The color of the blood offers important clues about the location of the bleeding.
Bright red blood, medically termed hematochezia, usually indicates bleeding lower down in the digestive system, such as the rectum or anus. Common causes include hemorrhoids or anal fissures, which are small tears that produce fresh blood often seen coating the outside of the stool or on toilet paper.
Dark red or maroon blood suggests a source of bleeding higher up in the colon or the lower part of the small intestine. This darker color results from the blood being partially digested as it travels a longer distance before excretion. If the stool is black and has a tar-like consistency, it is called melena and typically indicates bleeding in the upper gastrointestinal tract, such as the stomach or esophagus.
Distinguishing between blood and red food coloring can sometimes be difficult, but blood is often accompanied by other symptoms. Unlike food coloring, blood will not dissolve in the toilet water. It may also be mixed consistently throughout the stool rather than appearing as undigested flecks. Any suspicion of blood, particularly if accompanied by other changes in bowel habits or systemic symptoms, requires immediate medical evaluation.
When to Consult a Healthcare Provider
A transient change in stool color that resolves within a day or two after adjusting diet is generally not a cause for concern. However, persistence of an unusual color, especially reddish or orange, warrants a medical consultation. If the color change is accompanied by systemic symptoms, it may signal a more serious underlying issue.
Specific warning signs that necessitate professional evaluation include severe abdominal pain, persistent vomiting, or unexplained weight loss. The presence of visible dark red or maroon blood, or stool that appears black and tarry, should prompt immediate medical attention. Likewise, any persistent pale, clay-colored, or light orange stool not explained by diet or medication should be discussed with a healthcare provider, as it may indicate an issue with bile production or flow.