Black stool after taking a multivitamin

Iron is a common reason stool becomes darker after starting a supplement. The change may begin after the tablets are introduced and can continue while they are taken. Stool caused by iron is often dark but still formed, whereas melaena from upper digestive bleeding is typically jet black, sticky, and tar-like, often with an unusually strong smell. Colour alone cannot confirm the cause. Other explanations for bleeding include gastritis, Helicobacter Pylori Infection, or a Peptic Ulcer.

Check the label for iron and note when the colour change began. Do not take extra doses or stop a prescribed supplement without speaking with the prescriber. Keep a record of stool appearance, abdominal discomfort, nausea, medicines, and any use of anti-inflammatory painkillers. Arrange clinical advice if the colour persists after the supplement is paused as advised, keeps recurring, or is difficult to distinguish from tarry stool. A clinician may review your medicines and decide whether an examination or stool and blood testing is appropriate.

Seek urgent medical care for black tar-like stool, visible blood, vomiting blood or material resembling coffee grounds, faintness, marked weakness, breathlessness, confusion, or severe or worsening abdominal pain. Do not drive yourself if you feel faint. These symptoms can occur with significant digestive bleeding and should not be attributed to a multivitamin without assessment.

Ask whether your product contains enough iron to explain the change, whether another medicine could contribute to bleeding, and which stool features should trigger urgent review. Ask how long to continue the supplement and whether you need testing for gastritis, Helicobacter Pylori Infection, or a Peptic Ulcer.