While the fasting glucose and A1c tests have long been the gold standard of diabetes evaluation and monitoring, the fasting insulin test is becoming an excellent tool for helping understand glucose and insulin relationships.  The fasting insulin level is a great way to see what the insulin level is after a night of fasting when insulin levels should fall to their lowest levels.  Food intake triggers the pancreatic release of insulin, so getting insulin tested after any dietary intake will skew the results, making them completely invalid.  

Dr.  Joseph Kraft was one of the early pioneers of insulin testing; with more than 14,000 participants, he studied glucose and insulin levels before and after dietary intake.   He identified 4 main responses of insulin:  one distinct normal insulin pattern (I) called “euinsulinemia” and three abnormal patterns (II-III-IV) of hyperinsulinemia.  Hyperinsulinemia occurs for years prior to a diabetes diagnosis.

Using insulin testing and monitoring over time can reveal the development of diabetes since insulin levels climb over time in response to high carbohydrate dietary intake.  The more carbs consumed, the more insulin is released from the pancreas.  Over many years, this effect has worsened, resulting in poor glucose management.  It’s currently estimated that 75-90% of Americans have some form of insulin resistance, metabolic syndrome, and/or pre-diabetes/diabetes.  This epidemic of metabolic dysfunction requires us as healthcare providers to be more vigilant than ever before, using all the tools we can to help guide and educate our patients.

The normal lab reference range for fasting insulin is about 2 – 20 mcU/mL, with some variation, depending on the specific laboratory.  

However, more and more literature indicates that insulin levels 7 or higher indicate early insulin resistance; combined with markers of metabolic syndrome, it becomes quite clear how significant the impacts are to the patients.  Markers of metabolic syndrome include hypertension, impaired fasting glucose, large abdominal circumference, and elevated triglycerides.  If a patient exhibits any 3 of these conditions, they HAVE and should be diagnosed with metabolic syndrome, taught how to alter dietary intake, and how to monitor and prevent further progression.  

Testing insulin levels annually is typically sufficient for most patients.  See our nutrition course for more info on insulin testing and teaching patients how to use low-carb diets.