The title of this NACBLOG post is a question that was recently posted on the AACC chemistry list serv. Does Circadian Rhythm Impact Fasting Blood Glucose Testing?

What is your response? Check back for our response on Monday, April 30, 2012.

Yes, circadian rhythm does impact fasting plasma glucose levels.

In an article published in 2000 (JAMA 284:3157, 2000), the frequency of hyperglycemia (glucose =>126 mg/dL) in the study populations was higher when drawn after an overnight fast (2.8%) than when drawn as a fasting afternoon sample (1.4%).

Therefore if a fasting plasma glucose measurement is used to screen for diabetes, an overnight fast is preferred to sampling in the afternoon. In the quoted study, the subjects drawn in the AM had fasted for a mean of 13.5 hrs and the subjects drawn in the afternoon had fasted for a mean of 7 hours.