DEAR DR. DONOHUE: I have a friend whose glucose tests taken in the morning range from 140 (7.8) to 200 (11) and are never in the normal range. He is constantly thirsty and has other diabetes symptoms. His doctor ordered a hemoglobin A1C test, which came back as 5.2. The doctor told him that they no longer do the fasting blood sugar test, only the HbA1C, and that he is not diabetic, since his test is normal. Has testing for diabetes changed? Should my friend consult another doctor? — L.P.

ANSWER: Up until 2010, doctors diagnosed diabetes on the basis of blood sugar (actually plasma glucose). A relatively new test, hemoglobin A1C, HbA1C or just A1C, has been added to the criteria for both diagnosing diabetes and monitoring diabetes control in the past three or four months. Hemoglobin is a large molecule inside all red blood cells that grabs oxygen from the lungs and releases it to all parts of the body as blood circulates. Blood sugar coats hemoglobin. Since red blood cells last 120 days, the percentage of hemoglobin coated with sugar indicates how well-controlled diabetes is. An acceptable control level is one that is 7 percent or less.

Fasting blood sugar, the specimen taken after at least eight hours of not eating, is still used for diagnosing diabetes. A level of 126 mg/dL (7.0 mmol/L) or higher lands one in diabetes territory.

A second way to diagnose diabetes is to give a person 75 grams of glucose (sugar) to eat and test the blood two hours later. A value of 200 (11.1) qualifies as diabetes.

Now a third way of making the diagnosis is employing HbA1C. One selling point for using it is that there’s no requirement for fasting. HbA1C of 6.5 or greater makes the diagnosis.

Your friend is a diabetic. His fasting blood sugar qualifies him as being one. Furthermore, he has a diabetes symptom — perpetual thirst. He probably has to urinate frequently, another diabetes symptom. The fact that his HbA1C is normal doesn’t cancel these facts. That test is only one of three. He should see another doctor.

The diabetes booklet guides people through this prevalent and difficult illness. Readers can obtain a copy by writing: 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: A friend of ours is in a nursing home with pneumonia. We’re afraid to visit her. Is pneumonia catchy? — A.M.

ANSWER: A huge number of different germs cause the many different kinds of pneumonia. A blanket statement on transmission, therefore, is impossible. The pneumococcus (NEW-moe-KOK-us) bacterium is a prominent cause of pneumonia, especially in adults and older adults. This germ can be spread in droplets coming from a cough or sneeze. However, 24 hours of treatment renders the patient no longer a transmitter.

You can bank on it that a hospital or a nursing home will not let you visit any patient who might be at risk of spreading any infectious disease.

DEAR DR. DONOHUE: When donated blood mixes with the patient’s blood, is there a possibility that the patient inherits some of the donor’s characteristics?

Please clue me in. — D.G.

ANSWER: There’s not even a remote chance that a blood transfusion promotes changes in the recipient’s characteristics. Most blood transfusions are red blood cells only. Those cells have no genetic DNA.

Even if white blood cells, which do contain DNA, are transfused, that DNA does not become incorporated into the recipient’s DNA. This is true for all transplants, including organ transplants.

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.