Hello, I m glad to hear you that your overall health is excellent and I m sorry that you are experience these troubling symptoms recently. Diarrhea along with bleeding suggests inflammation in the intestines. This is often infectious, especially if it has only been occurring for a few days. Both viruses and bacteria can cause enteritis (inflammation of the itnestines) and this is generally self-limited. Bacterial enteritis may require an antibiotic for several days. There are also autoimmune conditions like Crohn s disease and ulcerative colitis that cause inflammation in the intestines. There are some blood tests that can give an indication of whether or not the inflammation in your body is very high (ESR is an example). These autoimmune conditions tend to occur over longer durations (at least a few weeks). The diagnosis is generally made by biopsy with a colonoscopy. If I was seeing you in clinic, I would treat you for an infectious enteritis if your symptoms have only been going on for a few days. If your symptoms have been going on for a longer duration, I would obtain some blood work, stool tests, and I would likely refer you to a Gastroenterology for a colonoscopy. I hope this sheds some light on the approach to your symptoms.