August 22, 2001
Diagnosis and Symptoms
Question from Greenville, South Carolina, USA:
I am 29 years old and was diagnosed with type�2 diabetes about six months ago, but my nurse-practitioner, sister and CDE, and I am beginning to suspect that I may have either a type 1 on a long honeymoon or type 1.5. (There is no doubt that I truly have diabetes, not IGT [Impaired Glucose Tolerance]. My readings for the three-hour glucose tolerance test were 339 mg/dl [18.9 mmol/L], 220 mg/dl [12.2 mmol/L], and 178 mg/dl [9.9 mmol/L]). I have always been underweight (at this time I am about 20 pounds underweight), have no family history of any diabetes or hypoglycemia, and I am Caucasian. I am currently on Starlix [nateglinide] before meals, and it is working very well for me so far. Two months ago, my hemoglobin A1c was 4.6%. I know this is really low for someone with diabetes, but I actually don't have that much trouble with low blood sugars, if I eat enough at mealtime. Is there any way for me to find out exactly which type I am? What tests should I ask for? Should I be concerned with this A1c?
Very good questions. First, do not be worried about the low hemoglobin A1c readings, especially if you are not having low sugars which are clinically evident. It does sound to me like you have a form of Late-onset Autoimmune Diabetes of Adulthood (LADA). This group of patients have onset of disease later than is typical for type�1 patients. They may even have sugars which are well treated with oral agents initially. However, over time, beta cell function falls and the patients reach insulin dependent status. Immune markers are evident with GAD65 antibodies most likely to be positive. You can also measure an insulin or C-peptide response to a mixed meal or oral glucose. However, insulin and C-peptide levels may not be markedly abnormal early.