There are many possibilities. Often, the patient is not allowed to take anything by mouth, BUT it may be necessary to provide nutrition or medicine or blood transfusion by vein. Keeping the D5W glucose solution running in by a slow drip allows for immediate access to the vein for all of the above. Anything given through an IV (intravenous) route works fastest to treat the patient. If the IV line is open and a patient needs to get more than one medicine by IV, keeping an open drip of glucose avoids having to stick the patient's veins many more times.