Red coloration, similar to fresh blood |
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Black coloration, similar to melena |
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False-positive results to fecal occult blood test |
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* Several reports have described cases of very red-appearing stools associated with cefdinir, apparently caused by an interaction with iron supplements or iron-containing infant formula[1-3]. Rifampin can cause orange discoloration of stools as well as urine. Other antibiotics in red vehicles (eg, cherry syrup) may cause a red tint to the stool, especially in infants or others with a fast transit time. Antibiotics can also trigger true gastrointestinal bleeding (Clostridioides difficile colitis). Therefore, red-appearing stools should be evaluated with guaiac or other tests for blood.
¶ Oral iron supplements cause false-positive results for some traditional kits for occult blood testing. However, this is not the case for contemporary test kits (eg, Hemoccult II, Hemoccult Sensa, HemoQuant).