Proper preparation is critical to the success of the colonoscopy. Patients are urged to inform their physician about any medications they are taking, including aspirin, arthritis medications, anticoagulants (drugs that prevent the blood from clotting), diabetes medications and vitamins that contain iron. They should disclose information about any allergies they may have to drugs or other substances. They should also inform their physician of medical conditions that may require special attention, such as heart disease or lung disease.

Patients must take steps to ensure their colon is clear of stool and fluids that can obscure the view of the colon’s interior lining. Although this can be uncomfortable, it is essential that the colon be clean for the colonoscopy to provide adequate information. The physician will give the patient detailed instructions on how to prepare for the test.

During the 24 hours prior to the exam, patients are likely to be asked to:

• Stop taking iron pills or medications containing iron. Iron alters the color of the colon lining. It is likely that patients will be asked to give up these sources of iron for several days before the test. Patients may be instructed to stop taking other over–the–counter and prescription medications as well. The patient’s physician will provide specific instructions regarding mediation restrictions.
  
  Patients who have diabetes or who take anticoagulants (including aspirin) may have to prepare for the test in a slightly different manner. This should be discussed with a physician at least a week before the scheduled date of the colonoscopy.
  
  
• Take laxatives. Most patients will take a laxative the night before the exam and possibly the morning of the exam. The physician will instruct the patient on the type of laxative to use and the schedule. In some cases, a patient may also need an enema (which involves inserting fluid into the rectum) to clear the colon. In addition, the U.S. Food and Drug Administration recently approved the use of sodium phosphate in tablet form for bowel cleansing in individuals who are unable to tolerate liquid preparations. The cleansing process will vary by patient and will be prescribed by the physician performing the procedure.
  
  Patients will likely spend a significant amount of time in the bathroom in the 24 hours prior to testing. Although patients may find this unpleasant, it is crucial to   clean out the colon so the physician can get a detailed look at the colon wall.
  
  
• Avoid eating solid foods and opaque liquids until after the procedure. Some physicians may recommend that patients avoid these for one to three days prior to the test.
  
  
• Drink and eat only clear, nonalcoholic beverages and foods. These might include water, tea, gelatin that is not red (as red can be mistaken for blood), clear broth and certain juices. Patients must avoid all red liquids. The physician will instruct the patient on specific dietary guidelines and restrictions prior to the colonoscopy.