The medical system is very slow to change.  It is well represented by the remark, “This is the way it’s done because this is the way it has always been done”.  The time-honored approach to doing blood tests is to have them done after a 10 hour fast (or more).  But why are fasting blood tests ordered?

The purpose behind doing blood tests is to determine how the patient’s body is performing. How the body works from a metabolic standpoint can give the healthcare practitioner a lot of valuable information.  However, when a person fasts, the metabolic system slows down. As a result, in many cases, the sugar levels, insulin levels, and triglyceride levels are all within normal limits.  There are a number of people who will have normal fasting blood tests but will exhibit very high spikes in these particular tests after eating.

Armed with this information, the practitioner can take a completely different approach to treatment and prevent a patient from developing diabetes.  As it is, when testing for diabetes, a 2-hour post-prandial (after-eating) test is often ordered or else the archaic 5-hour glucose tolerance test.  So why not eliminate those 2 tests and instead order blood tests after eating?  A lipid panel is perhaps the best way of screening for the potential development of type II diabetes.  Metabolic Syndrome is known to be the number one predisposing factor to getting diabetes.  It is manifested by a low HDL cholesterol and high triglyceride level.  Insulin is the most common reason why people have low HDL cholesterol and insulin is the number one cause of type 2 diabetes.  By artificially keeping the triglyceride level low by fasting, the diagnosis of Metabolic Syndrome may be missed.

Interestingly, many doctors will indicate that the reason why they do fasting blood test is to check the total cholesterol level.  What they may not be aware of is that eating does not directly raise cholesterol levels.  Is it possible that they are not even sure why they do fasting blood tests?

As a reminder, for those of you who are on thyroid medication, please remember to take your medication on the day of the test even if it is ordered fasting.