Since tarry stools can indicate a health issue, it would be wise to notify a doctor. Tarry stools are a symptom of bleeding in the GI tract, according to the National Institute of Health.
Eating certain foods can also cause bloody or tarry stools. This includes licorice, berries and beets. When a person experiences bloody or abnormal stools, they should contact their doctor as soon as possible. Only a doctor can diagnose the reason for the tarry stool. The doctor may order specific tests such as a colonoscopy. They may also request stool samples, do blood work or do a barium scan.