What should you know about black stool during period?

Menstrual blood can make the toilet bowl, tissue, or outside of a stool look darker, especially when bleeding is heavy. Stool that is genuinely black throughout, sticky or tar-like, and unusually strong-smelling is different. It may reflect digested blood from the stomach or upper intestine. Possible causes include irritation of the stomach lining, a Helicobacter pylori infection, or a peptic ulcer.

Iron tablets, bismuth-containing medicines, and some dark foods can also turn stool black without bleeding. Do not assume a medicine or food is the explanation if the stool is tarry, the change is new, or you feel unwell.

Look at the stool itself rather than only the toilet water, and note its colour, texture, smell, and whether the change happens again. Review recent iron or bismuth use and any dark foods, but do not stop a prescribed medicine without medical advice. Arrange prompt clinical advice if the stool appears tarry or the reason is unclear. A clinician may ask about stomach pain, vomiting, medicines, and previous digestive problems, then decide whether examination or testing is needed.

Seek emergency care if black stool occurs with dizziness, fainting, marked weakness, confusion, shortness of breath, a fast heartbeat, severe abdominal pain, vomiting blood, or vomit that looks like coffee grounds. These symptoms can accompany significant digestive-tract bleeding. Seek prompt medical advice for repeated black stools, even if period symptoms are also present. Heavy menstrual bleeding does not explain away signs that the stool itself may contain digested blood.

Ask whether the appearance could be caused by menstrual contamination, iron, bismuth, or digestive bleeding. Tell the clinician when the change began, whether the stool is tarry, and whether you have pain, nausea, vomiting, dizziness, or unusual tiredness. Bring a list of medicines and supplements, including anti-inflammatory painkillers and blood thinners, because these details can affect the assessment.