As we have seen in previous articles involving stool, a lot of information can be given to doctors when they ask about frequent bowel movements as well as the color of the stool. Dark stools present a challenge to doctors because it is a very subjective complaint from patients at times and many may be embarrassed even to bring up this complaint to doctors. Dark stools can come from a realm of different possible conditions, but the common denominator with this condition is to go to a doctor to rule out more concerning conditions immediately . Here, I will present you with a few different causes of black stool and what you need to do about each condition.
One of the most obvious and most severe reasons that you may be having dark stools could be due to internal bleeding . You may think that all types of intestinal bleeding should present with bright red stools but in reality, the color of your stools depends on where the bleeding is occurring. If you have bleeding near your anal canal, the blood with not have time to oxidize and will still be bright red. If it is from another between your stomach and your duodenum, there is a good chance that stomach acid will have had an opportunity to interact with the heme in blood and cause it to darken and this is why the stools will be black. 
There are many common causes of upper GI bleeding that you will need to have an expert to investigate to get the appropriate treatment. Some of the most likely could be something like gastric or peptic ulcers in the stomach or small intestine. Upper GI bleeding could be caused by drinking large amounts of alcohol, taking too many painkillers or even from a bacterial infection like H. pylori. This is a bacteria that is found mainly in developing nations and is transferred through contaminated food and water. The bacteria is hard to kill because it creates a protective barrier between itself and the stomach acid that should destroy it so long-term antibiotic therapy should be prescribed. 
A doctor will be able to tell you about what course of action to take best suited for your particular past medical history. He will find necessary clues through a history and physical examination and may also need to do an endoscopy in order to determine if there are any observable locations of bleeding in your throat or stomach. 
Medication Side Effect
Even if dark stools is a big cause for concern, it can also be from causes that are more benign in nature and doctors and patients need to remember that there are possible side effects from certain medications that can turn stools black. Two of the most common supplements that are used throughout the world would be iron tablets and charcoal.
Iron supplementation will turn stools dark in color due to the increase in the concentration of ferrous sulfate. Our body naturally digests and processes some of the iron but most of the time, doctors attempting to treat patients suffering from anemia will give a higher dose of iron. This is to account for the fact that not all iron that is ingested will be digested and processed so by giving a higher dose, you are making up for the deficiency you may have. Women are more prone to anemia so if you feel fatigued or constantly without energy, go to your doctor to get worked-up for an iron deficiency. 
Charcoal is another compound that is still used in modern society as a natural treatment for GI complications like diarrhea. It will be normally given in an activated charcoal preparation and it is designed to cause constipation in patients. The side effects of this medication would be very dark stools that should resolve within 48 hours after stopping the medication.  There are better medications on the market to address the same symptoms so I would recommend those over activated charcoal when possible.
The last cause of black stool that I will investigate further is from dietary habits that a person chooses. As we have seen in previous articles, many of the long-term problems related to frequent bowel movements can be linked to the diet we follow. Numerous studies have shown that dietary choices can either promote health or can elicit bad outcomes so it is very important to be mindful of the foods you consume.
In this circumstance, the types of foods we decide to consume could lead to color changes in the stool we produce. This is an entirely benign finding and will resolve as soon as we are able to digest the food. Some of the more obvious foods that can lead to darkening of stools would be foods like beets, blueberries or black licorice.