A1C tests might not be accurate in older adults

A1c testing

Dear Doctors: My blood tests show that I am prediabetic. I am puzzled because I am not overweight, I get plenty of exercise and I eat quite a bit of fiber every day. I don’t eat many sweets, but I do drink wine with meals. I am 77 years old. Is there some other preventive measure I can take?

Dear Reader: When someone has prediabetes, it means that their blood sugar levels are consistently higher than normal, but they have not yet reached the threshold that is characterized as diabetes. The diagnosis is basically a warning that they are at risk of developing Type 2 diabetes. That’s when the body either doesn’t make enough insulin or no longer has an adequate response to the hormone.

As we have discussed here before, blood sugar levels are an important metric of health and well-being. Over time, elevated blood sugar can cause serious health problems. They can lead not only to Type 2 diabetes, but also can put people at risk of nerve impairment, heart disease, kidney disease, vision loss and stroke.

The condition is often diagnosed with an A1C test, which is a blood test that estimates someone’s levels of blood glucose over the prior three months. Another approach is a fasting plasma glucose test. It is a finger stick test that measures blood sugar at a single point in time. As the name suggests, it is performed when someone has not eaten for at least eight hours, which is when blood glucose levels should be at their lowest. Blood glucose is measured in milligrams per deciliter, or mg/dL. A value below 100 mg/dL when in a fasting state is considered normal. Results between 100 and 125 mg/dL are considered to be prediabetes. If fasting blood sugar levels consistently top 125 mg/dL, a diagnosis of diabetes enters the picture.

Advice to people with prediabetes centers on the things you are already doing: Maintain a healthy weight, get regular exercise, avoid added sugars and eat high-fiber foods. Interestingly, several studies have indicated that wine, when consumed with meals, can have a positive effect on glucose metabolism. And that brings us to the question of age. Newer research has found that for older adults diagnosed with prediabetes, the risk of the condition escalating to Type 2 diabetes is fairly low. In a study by the Centers for Disease Control and Prevention, which followed 50,000 adults between 70 and 90 years of age with prediabetes, just 5% had progressed to Type 2 diabetes at the end of two years.

There is also evidence that A1C tests, which measure the percentage of glucose bound to hemoglobin, may not be as accurate in older adults. This is due to age-related changes to the life cycle of red blood cells. If your diagnosis was based on an A1C test, you might want to discuss this with your doctor. If your doctor believes you to be at risk of Type 2 diabetes, they may suggest an oral glucose tolerance test. Some people with prediabetes opt to use a wearable glucose monitor for a few weeks. The real-time results can reveal helpful information about the effect of diet, exercise and other lifestyle choices on glucose control.

(Send your questions to [email protected], or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Take the Next Step

Learn more about UCLA Diabetes Program.