June 27, 2002
Daily Care
Question from Florida, USA:
I have been told that I have prediabetes so I monitor my own blood sugar. My fasting blood sugar averages about 124 mg/dl [6.7 mmol/L], and it runs less than 100 mg/dl [5.6 mmol/L] during the day and at bedtime. I do not understand why my morning fasting sugar level is higher than during the day.
Answer:
A fasting or random blood sugar level performed on a meter is not accurate enough for diagnosing diabetes due to its variability. See Classification and Diagnosis of Diabetes. I’d ask your doctor for a lab determination of a fasting blood sugar with an urinalysis to definitively rule out the diagnosis of abnormalities in glucose metabolism.
To answer your second question regarding why fasting values are higher than values recorded over the daytime, I must say that it is typical of diabetes or an impaired glucose tolerance. It’s due to an overproduction of sugar by the liver during the late nighttime (dawn phenomenon).
MS