DEAR DR. DONOHUE: For years I have checked my blood sugar on my own meter and made adjustments to my diet and medicine as needed. The meter gave me results in numbers of milligrams. Now my doctor has me going to a lab, where the results are in percentages of hemoglobin A1C. Why the change? I don’t understand the new numbers. How do they correspond to the old ones? Do I throw out my meter? — H.G.

ANSWER: Hemoglobin is a huge molecule inside red blood cells that holds on to oxygen when blood passes through the lungs. Sugar also sticks to hemoglobin. Think of it as a glazed doughnut. That’s hemoglobin A1C.

The beauty of HbA1C lies in its ability to tell you how well or badly controlled your blood sugar was in the previous two to three months. It indicates the average value of your sugar in that period. The advantage of this is a clearer picture of whether medicine, diet and activity are keeping your sugar in a safe range. A single measurement of sugar can be misleading. It provides information on only a very short time span. It doesn’t provide the big picture that HbA1C does.

Another advantage of the test is not having to fast before blood is drawn, and not having to be at the lab early in the morning. Furthermore, it provides a better estimate of your risk of coming down with diabetes complications like kidney damage, loss of sight, heart and nerve disease.

Don’t throw away your meter. You still need to know what your blood sugar is on a daily basis. You have the HbA1C test done only a few times during the year.

Blood sugar values corresponding to HbA1C readings are: 5 percent, 97 mg/dL (5.4 mmol/L); 6 percent, 126 (7); 7 percent, 154 (8.6); 8 percent,183 (10.2); 9 percent, 212 (11.8).

The diabetes booklet gives a comprehensive treatment of this common illness. It doesn’t speak of HbA1C, though. To obtain a copy, write: Dr. Donohue — No. 402, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: In my early 20s, my appendix burst. I was left with a large scar and adhesions in my abdomen. I am now 58 and have not had a colonoscopy exam. I wonder if the scar would make the exam impossible or dangerous. — H.J.

ANSWER: You have no worry. The scar isn’t a contraindication to having the exam. Neither are the adhesions.

DEAR DR. DONOHUE: I am a 77-year-old woman who has lived in Florida for the past five years. I am in very good health. My children want me to move closer to them, in upstate New York. I grew up in Michigan, so I know what the weather will be like. My question is: Do I attribute my good health to living in a warm climate, or will it make no difference if I move and continue my way of keeping my health? — M.B.

ANSWER: Climate has some effect on health, I’m sure. However, my grandfather lived in Michigan, and he died at 97. A better reason for making or not making the move is which place will make you happier. Contentment has an even greater impact on health than climate.

Why not spend a few weeks this winter with your children and see how you like upper New York?

DEAR DR. DONOHUE: A friend and I visit a rest home every Thursday. He plays the keyboard, and I sing. I am upset because when some of the people in wheelchairs go to sleep, their heads fall backward or forward. Are there no head rests on wheelchairs? I hope you can enlighten me. I am 82. — J.B.

ANSWER: I can’t enlighten you. However, your idea is a good one. I hope a manufacturer of wheelchairs reads your suggestion and acts on it.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.