stomach

Black stool usually indicates blood in the stool may be a sign of rectal bleeding or gastrointestinal bleeding. Certain conditions may lead to bloody diarrhea. Any bleeding symptom needs prompt professional medical advice.

http://www.wrongdiagnosis.com/sym/bloody_stool.htm

Another possible reason for blood in stool would be hemorrhoids, if you have been straining during the diarrhea the last couple of days.

http://digestive.niddk.nih.gov/ddiseases/pubs/hemorrhoids/

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are there any other signs that would indicate gastrointestinal bleeding , all help would be usefull

You say you had food poisoning, what made you think that? Did you eat something that was bad? Gastrointestinal bleeding can be for several reasons. Symptoms depend on the location of the bleeding within the digestive tract.

You mentioned black stool. The main reason for black stool is blood. Where it would be coming from, that's what you need to find out. Without being seen in person that would be even hard to guess.

Here is a link that does list causes of Gastrointestinal Bleeding

http://www.emedicinehealth.com/articles/10509-2.asp