February 22, 2002
A1c (Glycohemoglobin, HgbA1c), Diagnosis and Symptoms
Question from Cozad, Nebraska, USA:
You encouraged me to see another doctor, so after almost six months, I got up my courage and went to see a doctor in another town who diagnosed type�2 diabetes yesterday. My A1c is 7.2%, and I had a random glucose of 198 mg/dl [11 mmol/L]. He said this, along with my past readings from my previous doctor is a definite diagnosis. My past test had shown a fasting (lab )glucose of 157 mg/dl [8.7 mmol/L], and a two-hour reading on a glucose tolerance test of 208 mg/dl [11.6 mmol/L], but my previous doctor said that since my A1c at that time, was 6.2%, I did not have diabetes. This new doctor said you shouldn’t use the A1c as a way to diagnose diabetes, and in the honeymoon phase it would be low.
Answer:
Since the hemoglobin A1c measures average blood glucose over a period of about three months, it can be used to evaluate how long and how high blood glucose levels have been, but it cannot be used for diagnosing diabetes. So, as your new doctor has told you, if your blood glucose is low or normal a lot of the time, the A1c would not reveal your problem. Diagnosis, according to the American Diabetes Association Classification and Diagnosis of Diabetes Guidelines, is based on symptoms along with blood glucose levels.
You could print out these guidelines and send them to your previous doctor. Perhaps this might prevent others like you from not being properly diagnosed and receiving early treatment.
SS
