Black stool with food poisoning: what to know

Food poisoning more often causes nausea, vomiting, diarrhoea, abdominal pain, or fever. Black colour can sometimes follow dark foods or medicines, but black, sticky, tar-like stool may mean bleeding in the upper digestive tract. The timing after a meal does not prove that food poisoning caused the colour. A clinician may need to separate dehydration from bleeding and consider other digestive conditions.

Record the stool’s colour and texture, when symptoms began, what you ate, and any medicines such as iron or bismuth. Sip fluids if you can keep them down; oral rehydration therapy can replace water and salts lost through vomiting or diarrhoea. Avoid alcohol and anti-inflammatory pain medicines until assessed. Do not use leftover antibiotics or anti-diarrhoeal medicine without professional advice.

Go to urgent care for black tarry stools, blood in vomit, faintness, confusion, severe or worsening abdominal pain, very little urine, or inability to keep fluids down. Fever with marked weakness, bloody diarrhoea, or signs of dehydration also needs prompt review. Severe dehydration may require IV fluid therapy, while the cause of black stool may require examination and testing.

Ask whether your symptoms fit food poisoning, whether the stool could represent bleeding, and which fluids or medicines are suitable. Tell the clinician about recent meals, travel, sick contacts, vomiting, diarrhoea, fever, and all medicines.