You will need to remain at the hospital or outpatient center for several hours until the sedative wears off. That's why it is especially important to follow the instructions given to you exactly, to make you preparation of the bowel for colonoscopy the best that it can be. Your colon must be completely empty for the colonoscopy to be thorough and safe. To prepare for the procedure you may have to follow a liquid diet for 1 to 3 days beforehand. You may need to take laxatives or an enema before the procedure.
Colonoscopy is quite safe.
However, as in any invasive procedure, there is always a possibility that problems can occur during and after the procedure. Physicians review the risks and anticipated benefits of the procedure with you beforehand, individualized to each person. As part of most hospital standards, you will be asked to sign an informed consent that basically outlines the general risks of gastrointestinal endoscopy. During the procedures there is a small risk of bleeding, more likely when a biopsy is taken or a growth removed. This is usually treated conservatively, but on extremely rare occasions a transfusion could be needed.