May 26, 2005
A1c (Glycohemoglobin, HgbA1c), Diagnosis and Symptoms
Question from England:
I was diagnosed with type 1 diabetes two years ago. I am 22 years old and my BMI is 22. When I was diagnosed with diabetes, my fasting glucose was 7.9 mmol/L [142 mg/dl]. After the glucose tolerance test, it was 17.9 mmol/L. [322 mg/dl]. My A1c was approximately 5%. I thought that to be diabetic, this had to be higher than 7%, but the doctors insisted that I was definitely diabetic and started me on mixed insulin injections morning and night.
I have been reviewed at regular intervals since my diagnosis. I have had numerous blood tests since my diagnosis and my A1c has always been 5%, but my sugars at the time of these blood tests have always been above 7 mmol/L [126 mg/dl] and on occasions 10 to 16 mmol/L [180 to 288 mg/dl]. When I do my blood sugars using my meter, my sugars are sometimes in the normal range, but sometimes they are high, between 7 mmol/L [126 mg/dl] and 14 mmol/L [252 mg/dl]. I only get hypoglycemic reactions about once every couple of months and they have never been severe. The lowest reading was 2.9 mmol/L [53 mg/dl].
My consultant is very puzzled and ran some more tests. He did a full antibody screen that was negative and he also looked at my fructosamine, which was also within normal limits. He also checked for hemoglobinopathies, which may lead to a false reading on the A1c, and which I don’t have. I only require eight units of insulin every day and I think it is making me gain weight. I gained 12 kg (26 pounds) in a month. I have heard of idiopathic diabetes when the antibodies are negative, but I thought that was only present in Asian and African people. I am Caucasian. I have no family history of diabetes. It is of great concern to me and to my consultant that I am not fitting any particular pattern he has ever seen or heard of. He cannot understand what is going on and his frustrations are worrying me.
So, how can I have a normal A1c and yet have very few hypoglycemic reactions and run high sugars frequently? Could I be having lows in the night I don’t know about? How accurate are A1cs? Why are my antibodies negative? Could I have idiopathic diabetes? Why am I only requiring eight units of insulin two years after diagnosis? I have read about LADA; could I have that? Does this picture fit anything you have seen before? Is there a chance that my diagnosis is wrong when we consider all these inconsistencies?
Answer:
My impression is that you do have type 1 diabetes and are in a honeymoon phase. The reason the A1c was never very high is that the diabetes may have been diagnosed before it rose. Remember, this notes the average daily blood sugar over the previous three months. Your repeated high blood sugars at other times should be enough to suggest you have diabetes. When therapy to relieve the hyperglycemia is instituted, it allows for the surviving beta cells to work more efficiently. The lack of antibodies does not rule out diabetes. It only helps if they are present. You may even need to drop your insulin dose further, especially in light of hypoglycemia and weight gain.
Unfortunately, I do not think your rather mild response rules out the diagnosis of diabetes. Normal glycated albumin or fructosamine levels only show an average daily blood sugar reading for the preceding two weeks. You know that those have been good because you have monitored the sugars over that time. The goal now is ride out the honeymoon phase as far out as possible. The duration of the response is dependent on having as good a level of control as possible.
JTL
