DEAR DR. DONOHUE: Help. I am a diabetic. I have asked four doctors this question and can’t get an answer. If I take my blood for a sugar test from my left index finger, the reading is 15 to 30 points higher than it is from the blood in my right index finger. Doesn’t blood have the same concentration of sugar in all parts of the body? – R.T.

ANSWER: That letter was printed a few months ago. I didn’t have an answer for the lady. I asked for help, and many wrote, including doctors and engineers. I appreciate the response, and now I do have an answer.

Home blood sugar monitors – glucometers – have made it possible for diabetics to gain strict control of their blood sugar and lessen the chances of diabetes complications. They provide an immediate and convenient blood-sugar reading so that the diabetic can adjust diabetes medicines or food intake.

These little devices are relatively inexpensive. They shouldn’t be expected to provide as precise a reading as a costly, laboratory machine. There can be as much as a 15 percent to 20 percent difference between two readings taken in immediate succession from the same or different finger. For example, if one reading registered 120, the next, quickly taken reading could be anywhere from 96 to 144. This is something people just have to live with. The readings are valid enough to guide people in making appropriate changes in their program either by increasing or decreasing medicine dose or calorie intake. They do a great service for all with diabetes.

For greater accuracy, it is important that the finger to be sampled is clean. Anything clinging to the skin can throw off a reading.

Once again, I want to thank all letter writers for contributing information on this matter, which had perplexed me. I’m sure R.T. is equally appreciative.

DEAR DR. DONOHUE: I have frequent cold sores on my lip. What can be done for this? – K.V.

ANSWER: Cold sores (also called fever blisters) are the work of the herpes-1 virus. Once people have been infected with this virus, it stays in their body for the rest of their life. It hibernates in nerve cells. From time to time, it wakes up and produces a cold sore. Close to 80 percent of the American population has been infected, but strangely enough, only 20 percent to 30 percent suffer from recurrent outbreaks.

Zovirax cream shortens the duration of an outbreak. Acyclovir, valacyclovir (Valtrex) and famciclovir (Famvir) tablets can do the same. If a person has six or more outbreaks in a year, then that person can consider taking a daily dose of oral acyclovir to suppress the outbreaks.

Sunlight is known to activate the virus. A person with frequent outbreaks should apply sunblock to the site of the outbreaks whenever he or she is going to be exposed to the sun.

I must mention the amino acid lysine. Readers always write me about it after this topic appears. The herpes virus needs arginine, another amino acid, to replicate. Lysine interferes with the absorption of arginine. That’s the theoretical reason behind the use of lysine for cold sores. It’s available over the counter. I am not as convinced of its effectiveness as some readers are.

DEAR DR. DONOHUE: I have polymyalgia rheumatica. Will it ever go away? It has caused me to give up golf. What do you suggest? I am currently taking prednisone. – J.A.

ANSWER: Soreness, stiffness and weakness of the shoulder, neck and hip muscles are the signs of polymyalgia rheumatica. It doesn’t appear until after age 50. In addition, people often are fatigued, have a low-grade fever and lose weight. Its cause is puzzling, but the immune system is implicated in some fashion.

You’re taking the right medicine – prednisone, one of the cortisone drugs. This medicine usually brings a rapid response, within a matter of days. However, it often must be taken for one to two years, and some have to take it as long as 10 years. To keep side effects to a minimum, after the initial symptoms are controlled, it is given in reduced doses or on alternate days.

Polymyalgia rheumatica goes away in time.

DEAR DR. DONOHUE: Can a sunken sternum be corrected? If so, how? I don’t like to go shirtless because of it. – S.A.

ANSWER: A sunken sternum (breastbone) can be fixed. It’s a relatively common congenital condition. It happens in one out of every 300 births, and it happens mostly to males. Surgeons can reconstruct the breastbone and can bolster its supports.

Sometimes the surgery has to be done when the sunken bone presses on the heart and lungs, and affects their functioning.

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