Hi, I understand your concern. Before running into final conclusions, I d ask to send the full colonoscopy report to me, so I can analyze the findings and compare with your clinical symptoms. Sometimes, there is a light bleeding after the colonoscopy procedure, which is clinically expressed with dark stool (due to laceration of colon mucosa). That will be going in a few days. Next, you say that your doctor suggested to take Miralax, which is a gentle laxative. This makes me think you are suffering of constipation or hard stool. Miralax will help ease bowel movement (bm). Hard stool or constipation might cause laceration of colon/anal mucosa ending up with light bleeding or dark colored stool. I advise to continue the medications and advice as given by your doctor. If black stool will appear again or no improvement, should ask to consult with your gastroenterologist for further evaluation. Wish fast recovery.