Hi Everyone,
Please do not panic and assume that black stool is always a sign of blood. Your stool can be black from iron supplements, black licorice, and pepto bismol. Many people are taking supplements now so the change can be from that. If you do suspect blood then you should see your doctor.
Here are some articles on things that can impact the color of your stools:
http://www.mayoclinic.com/health/stool-color/AN00772
http://ibdcrohns.about.com/cs/otherdiseases/a/stoolcolors.htm
There are other posts about the changes in color that you can find by using the search command on the upper right corner.
Let me know if you have any other questions,
Betty Kovacs, MS, RD