Patients who do not fast before a physical exam, according to Weill Cornell Medical College, may see artificial increases in cholesterol levels that can result in a skewed and inaccurate blood test. More often than not, patients who did not fast before their appointment are asked to reschedule and follow the fasting instructions.
Patients who are having blood tests, such as cholesterol, glucose and stool tests, are often asked to fast for at least 12 hours depending on their exam. Each patient may have to fast for a different amount of time. Some patients may not have to fast before their physicals at all. However, it is very important to drink water during this fasting period, according to One Medical. Phlebotomists may have an easier time finding fuller, bigger veins from which to draw the patient's blood.
Chewing gum, smoking, drinking juice, coffee, or tea, are also expressly forbidden from most fasting instructions. However, recent research suggests fasting may not be necessary for cholesterol tests. WebMD describes a study published in the Archives of Internal Medicine that "suggests that people may not need to fast before they get a cholesterol test." Patients should check with their physicians before their scheduled testing appointment to determine whether they are required to fast before their physical and how long they must fast.