Making the Diagnosis of Diabetes

Making the diagnosis of diabetes can be a bit confusing for a couple reasons. While the hallmark of diabetes is an elevated level of sugar (glucose) in the blood, hyperglycemia, glucose levels fluctuate quite widely. In even a normal person their glucose can often be high for brief periods during the day, particularly after large meals and injestion of large amounts of sugars. Therefore, while it seems straightforward that the diagnosis of diabetes should simply be to measure the level of sugar in blood, this can be quite misleading alone.

To avoid this confusion, other more reliable tests for diabetes have been developed. The main problem in patients with diabetes is that their body's production and reaction to insulin is impaired. In a normal individual, insulin is secreted to keep glucose within normal ranges, balanced with other hormones in the body. In response to consumption of carbohydrates, simple sugars and fats, insulin is secreted in increasing amounts to help the body deal with this intake and will help quickly bring levels into the normal range. Two tests in particular help challenge this system.

A fasting blood glucose measurement tests the blood glucose level after the patient has been fasting for 8-12 hours. Normally, in this fasting state the blood sugar should be in the low normal range because there has been no recent intake to increase levels. In diabetics, the imbalance of insulin with other hormones leads to elevated glucose levels despite the fact that no intake of sugar has occured.

Even more reliable, a glucose tolerance test challenges the insulin system. After testing fasting glucose levels, the patient is given a load of glucose (in a drink) and then the blood sugar levels are tested periodically at fixed time points. While normal individuals will quickly lower their blood sugar levels back to close to normal, diabetics will have high glucose levels for a prolonged time after this challenge. Glucose levels on this test above a threshold level is considered diagnostic of diabetes and is quite accurate.

Other tests are mostly used as screening tests, such as testing for sugar in the urine or ketones in the urine, but in and of themselves are not diagnostic. Others are frequently used to help guide treatment and to monitor the effectiveness of treatment, such as spot serum glucose measurements and hemoglobin A1C testing.

If you have questions about your risk for diabetes or your diagnosis of diabetes, ask your own personal treating physician(s) for guidance.