Eating iron-containing Vitamin C leads to weakly positive fecal occult blood test, may be due to the taking of iron can not be fully absorbed by the body, excess iron ions can decompose hydrogen peroxide and release oxygen, benzidine oxidation to benzidine blue and blue, that is, positive, which in turn leads to eating iron-containing Vitamin C leads to weakly positive fecal occult blood test. Fecal occult blood test is usually used to check whether there is bleeding in the intestines, and is usually implemented as an auxiliary diagnosis of colorectal cancer and intestinal bleeding. A weakly positive fecal occult blood test caused by taking iron-containing vitamin C is a false positive and does not reflect bleeding in the bowel. To avoid a weak positive fecal occult blood test caused by taking iron-containing Vitamin C, you can stop taking the medication three days before the test starts and stop eating foods that may cause a weak positive result, e.g., animal blood products, animal offal, etc., in order to ensure the accuracy of the fecal occult blood test. If the fecal occult blood result is abnormal, you should seek medical advice promptly to avoid delay.