What causes black stool in the morning?
Oct 13, 2022
Source: Cainiu Health
Dr. Zhao Haiming
Introduction
Passing black stool in the morning may result from consuming foods high in melanin or animal blood products the previous day. These substances appear black after intestinal absorption and metabolism. It could also be due to taking iron supplements or bismuth-containing medications, which cause this effect following intestinal processing and oxidation. Peptic ulcers can also lead to black stool in the morning, as bleeding occurs and is subsequently oxidized into sulfides, which are then excreted in the feces.
Black stool in the morning may be caused by dietary factors, medication, or possibly indicate a peptic ulcer.
1. Dietary factors
Black stool in the morning may result from consuming foods high in dark pigments the previous day, such as black beans, black sesame seeds, or animal blood products like pig blood, duck blood, or chicken blood. These foods can turn stool black during digestion and metabolism. This is usually normal and the stool color typically returns to normal after complete elimination.
2. Medication factors
Taking iron supplements, such as ferrous sulfate or ferrous succinate, or bismuth-containing medications like colloidal bismuth subcitrate, may also cause black stool. These medications can react in the intestine and undergo oxidation, leading to the observed discoloration. The stool usually returns to normal on its own after stopping the medication.
3. Peptic ulcer
Peptic ulcers, such as gastric ulcers or duodenal ulcers, can also cause black stool in the morning. These conditions may involve minor bleeding. The blood remains in the gastrointestinal tract for an extended period and is oxidized into sulfides, which are then excreted with the feces.
