Thursday, February 10, 2011

Diabetes and the Eyes: What is HbA1c? (Is that a new smartphone?)


No, it's not a new smartphone...or a new touchpad...or a new coffeemaker. Basically, HbA1c is hemoglobin attached to glucose (sugar) in the bloodstream. Why is this important? Well, a recent study published online in the journal Diabetes and Research and Clinical Practice mentions that "having a glycated hemoglobin (HbA1c) value above 8.0% significantly increases the risk for sight-threatening retinopathy (STDR) in patients with diabetes." (Direct Link =>

For those with diabetes, the HbA1c is the "three-month" average value that your family doctor or eye doctor looks at, while the fasting glucose is the "daily" value. Hemoglobin is in the blood. It is the molecule that carries oxygen from your lung to your body, and carbon dioxide from your body back to the lungs. If glucose (sugar) is in the blood, it forms an irreversible reaction with the hemoglobin, binding together. If you have a lot of sugar in your bloodstream, more of it will bind to the hemoglobin. Hemoglobin lasts for 2-3 months in the bloodstream. So when the doctor asks for the HbA1c test, he wants to know how your blood sugar has been doing the past couple of months. So, the fasting glucose will give the physician a snapshot of how your blood sugar levels are doing, while the hemoglobin (HbA1c) value tells the physician how the blood sugar has been doing for a longer period of time.

Example: For dinner the past two months, you've been eating a plateful of chocolate chip cookies. You forgot that you have your visit with the family doctor tomorrow, and feeling a temporary mode of healthiness, you decide to skip the plate of chocolate chip cookies and eat a big salad instead. Two weeks later after the doctor's visit, he informs you that your daily blood sugar level was outstanding!!! (Great job!!!) But just as you are about to celebrate, the doctor give you the news that he suspects your dietary habits have been substandard, due to the HbA1c results. (Not-so-good job.) The doctor reminds you that eating a plate of chocolate chip cookies may taste good, but it is not good for you, and educates you about the importance of a healthy diet and exercise and the possibility of using medications and/or insulin for type 2 diabetes if the blood sugar does not improve. The doctor schedules a visit in three months and asks that you see an eye doctor, foot doctor, dietitian, and considers consulting an endocrinologist if the blood sugar becomes difficult to control.

Glucose monitoring at home is a helpful tool in making choices when eating food and snacks. Many spikes in blood sugar levels, or a consistently high blood sugar level, is more likely to contribute to vision changes and physical eye problems relating to diabetes. So, the more stable and reasonable level the blood sugar, the better.

For diabetics (Type 1 or Type 2), it is important to have a dilated eye exam every year as well as the recommended visits and blood testing by your family doctor. This is especially important if you do not monitor your daily glucose levels at home. Sometimes (not always) there are physical signs in the retina and other parts of the eye that can indicate elevated blood glucose. However, these signs usually occur in individuals who 1) have very high blood sugar levels and don't know it, 2) have difficulty maintaining a low and stable blood sugar level or 3) have had diabetes for a number of years.

Eyesight is a precious gift. If there are any negative vision changes, it is extremely important to get your eyes examined right away. Some changes relating to decreased vision may be reversible, but sometimes it is not, meaning that lost vision may not be recovered even with prescribing "stronger" glasses.

So, when it comes to hemoglobin and HbA1c, remember: 8 (and higher) is bad, 7 isn't as bad, 6 is better and 5 is great! Your doctor will figure out your goals and which number is appropriate for you. So...which number are you?

Take care of your body...and your eyes!

And, in case you were wondering, HbA1c is not a new George Lucas droid, either.

Dr. Weaver