These are very worrisome signs that you could be having bleeding in your stomach or intestines. This can be life-threatening. Get medical help right away. There are some things that you may have taken by mouth like iron or bismuth subsalicylate that may also turn the stool black.
While the list below can be considered as a guide to educate yourself about these conditions, this is not a substitute for a diagnosis from a health care provider. There are many other medical conditions that also can be associated with your symptoms and signs. Here are a number of those from MedicineNet:
Peptic or stomach ulcers are ulcers are an ulcer in the lining of the stomach, duodenum, or esophagus. Ulcer formation is related to H. pylori bacteria in the stomach, use of anti-inflammatory medications, and cigarette smoking. Symptoms of peptic or stomach ulcers include abdominal burning or hunger pain, indigestion, and abdominal discomfort after meals. Treatment for stomach ulcers depends upon the cause.
Helicobacter pylori (H. pylori) is a bacteria that causes chronic inflammation (gastritis) of the inner lining of the stomach, and also is the most common cause of ulcers worldwide. About 50% of people in the world carries or is infected with H. pylori. Common symptoms of H. pylori infection are occasional abdominal discomfort, bloating, belching or burping, and nausea and vomiting. H. pylori infection is difficult to eradicate, and treatment is with two or more antibiotics.
Food poisoning is common, but can also be life threatening. The symptoms for food poisoning are fever, abdominal pain, headache, diarrhea, nausea and vomiting. Food poisoning has many causes, for example, chemicals (from toxic fish or plants) and bacteria (Staphylococcus aureus or Salmonella). Treatment of food poisoning depends upon the cause.
Hereditary hemochromatosis (iron overload) is an inherited disorder in which there is excessive accumulation of iron in the body. Individuals may have no symptoms or signs, or they can have severe symptoms and signs of iron overload. The most effective treatment for hemochromatosis is therapeutic phlebotomy.
At MedicineNet, we believe it is important to take charge of your health through measures such as a living healthy lifestyle, practicing preventative medicine, following a nutrition plan, and getting regular exercise. Understanding your symptoms and signs and educating yourself about health conditions are also a part of living your healthiest life. The links above will provide you with more detailed information on these medical conditions to help you inform yourself about the causes and available treatments for these conditions.