What Is Fasting Plasma Glucose?

Fasting plasma glucose (FPG) refers to blood glucose levels measured after a defined period of fasting.¹ Average FPG usually ranges between 80-90 mg/dL, meaning 80-90 milligram (ie, milligram is 1/1000 gram) of glucose present in a deciliter (ie, deciliter is 1/10 liter) of blood.² Measuring FPG levels is one of the diagnostic tests for diabetes.¹

How Is Fasting Glucose Measured?  

To measure FPG levels for the purpose of diagnosing diabetes, 8 hours of fasting (ie, no caloric intake) is required.¹ After fasting, a health care professional will draw blood from a vein, from which blood glucose levels will be measured.³ Glucometers and continuous glucose monitors should not be used for diagnostic purposes.

What Is Impaired Fasting Glucose?  

Impaired fasting glucose (IFG) in a diagnostic sense is defined as elevated FPG levels measuring between 100 mg/dL to 125 mg/dL.¹ IFG is one of the ways to diagnose prediabetes. Prediabetes does not meet the diagnostic criteria for diabetes but has glucose levels too high to be considered normal and is considered a risk factor for type 2 diabetes mellitus and cardiovascular disease. When IFG worsens and FPG measures above 125 mg/dL, diabetes is diagnosed.

Beyond the numbers, IFG signifies that the body experiences hyperglycemia (ie, high blood glucose levels) even in the absence of caloric consumption, when blood glucose levels should be low.⁴ Studies indicate that IFG is attributed to the decline in pancreatic b-cell function (responsible for insulin secretion), reduced insulin sensitivity of the liver (reduced responsiveness to insulin to take up glucose), and inappropriately elevated glucagon secretion (a hormone that signals that glucose should be synthesized).