Stools can give us a lot of insight into the status of our body. As we have seen in other investigations, frequent bowel movements can shed light onto some possible conditions that we may be suffering from. The foods we eat, the things we drink and potentially underlying pathologies can all play a role as to having such a condition. Not only is the frequency of stools a point of concern at times for patients, but the consistency and smell of the stools can also be a concern. If stools have a stringy shape, it can signify that we are suffering from potential bowel obstructions due to problems with our diets. Stools can also have a metallic smell which could be problematic at times. Here, we will explore some of the reasons why your stool has a metallic smell.
When it comes to drugs, there are some potential drugs that can cause your stool to become foul-smelling. Antibiotics are named because of their "anti-cell life" mechanism of action . Their goal is to kill cells but the ingredients that comprise most of these medications are unable to selectively attack only bad cells. What happens as a result is that the medications are able to kill not only bad microbes but also good microbes that help your body function. In the intestinal tract is where this effect is most obvious.
When the ratio of good to bad bacteria changes, there is a resulting change in the composition of microbes in the.intestine. This can lead to diarrhea, constipation, gas and foul-smelling stools. This is a common side effect of most antibiotics and the flora that once made up your intestinal tract will quickly normalize in a week or two. There are no risks to your body during this time period and it is only a matter of embarrassment and worry for patients as their body normalizes back to what it once was. 
Another potential source of why your stool has a metallic smell could be from iron supplementation that you may be taking. Women are more likely to suffer from anemia than men due to their menstrual cycles. Anemia is just a medical diagnosis for a condition where women do not have enough iron or hemoglobin in their blood . This can lead them to feel fatigued, without energy and pale. It is estimated that in the United States, 6 percent of the population meets the criteria for a diagnosis of moderate to severe anemia . In a traditional Western diet, there is an abundance of foods like vegetables and fortified cereals that are teeming with high levels of iron to make this problem less likely. If you looked at a country in the developing world, however, prevalence rates for anemia can be as high as 60 percent of the population.
When patients are prescribed iron supplementation to fight this anemia, what can occur is excess iron will be excreted through your intestinal tract and lead to a metallic smell in the toilet bowl when you are finished with your business. It is entirely without risk for the patient but can also be problematic and uncomfortable. 
Inflammatory Bowel Conditions
Another cascade of diseases that will be commonly associated with metallic-smelling stools can be linked to inflammatory bowel conditions. Diseases like Crohn disease, Ulcerative Colitis, or Celiac disease can all be associated with metallic-smelling stools because of the underlying pathology of what is happening. Here, this is a condition where bleeding occurs throughout the inflammation of the intestinal mucosa. When this occurs, patients are subjected to high amounts of bleeding within their stools. 
The metallic aroma that will come with this type of pathology comes from the abundance of hemoglobin and iron now in the stools. You may start to suspect that this could be a problem if you notice that your stools are a much darker color than usual. These will be diseases that manifest at a young age in patients and most cases are diagnosed by the time a patient reaches 30 years of age. The best way to avoid this side effect is to start treatment for the condition as soon as possible. The key to this is having a consultation with a gastrologist in order to determine what could be the cause of this strange sensation.  Symptoms will be an obvious sign of frequent bowel movements that may be darker than normal.
The last important differential that you need to consider when your stool has a metallic smell is the possibility of cancer. This will also increase bleeding through similar mechanisms like inflammatory bowel syndromes but the key difference is patients will typically be much older in age. It is common not even to start screening for the disease until a patient reaches the age of 50. A diet high in meats, especially red meat, and a family history can point to this condition as being more likely.