Diagnosis of Diabetes Mellitus using HbA1c


Q: First let me tell you that I am an RN. I recently went to my medical doctor because over the last 2-3 months I have been having shock-like sensations at random intervals throughout the day. He ordered lots of lab tests and did an EKG which was normal. My lab included a HgA1C test which was 6.7. My CBC was normal. My UA was normal. My cholesterol was high. My blood sugar was 97. It was not a fasting test. My T4 and TSH were within normal limits. He diagnosed me with DM on the results of the A1C. I know that the guidlines allow this, but my fasting bloods have never been elevated. My question is this, should I ask for FBS or GTT? I am not at all convinced that I have DM. No symptoms at all. He is treating the shock like symptons as Diabetic neuropathy. I am just totally confused. Part of his practice is a weight loss program ( I am over weight) and also a hormone replacement program, which he insists that I need. I am resistant just because I feel that perhaps I have been misdiagnosed. I Just would like have an opinion of what I should do from here. Thanks


A:   The HbA1c test is less reliable to diagnose diabetes than it is for follow-up care. Still, a HbA1c result greater than 6.1% is highly suggestive of diabetes. Generally, a confirmatory test would be needed before diagnosing diabetes. Random plasma glucose >=200 mg/dl (11.1 mmol/l) is confirmatory of diabetes, but your random level is only 97 therefore this does not meet the criteria. It may be that you have impaired glucose tolerance as part of the metabolic syndrome. Because you do not have symptoms of hyperglycaemia at present, I advise attending your family doctor for either a fasting plasma glucose level, or an oral glucose tolerance test. It is essential to confirm or exclude a diagnosis of diabetes due to necessary future follow-up and implications with medical insurance.

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