Is balck stool common in firs weeks of pregnancy?

Iron in pills: If you are taking iron pills, your stools are often black. Iron pills can make you constipated, as well. If you are not taking iron pills (or vitamins containing iron), then it needs to be checked. The most common cause is bleeding from the stomach or upper intestine. Tests for occult blood can be bought at any pharmacy. Fortunately, iron ingestion is more likely.

Iron in vitamins: may cause it. Black, tarry, malodorous stool can be related to GI bleeding.