DEAR DR. DONOHUE: Why do my ankles swell so much during the day? I am 72 and in good health. When I wake in the morning, my ankles are normal size, but by the time I go to bed, I have a hard time getting my shoes off. I have yearly exams, and they are always good. – B.V.

ANSWER: Swelling results when fluid comes out of capillaries, the tiny blood vessels that connect arteries and veins. Fluid seeping out of capillaries is normal. That’s how body cells and tissues obtain their nutrition. However, when capillary fluid pressure rises, then too much fluid leaves, and the feet and ankles bloat.

Heart failure, liver disease and kidney disorders cause fluid retention in the ankles and feet. You have a yearly examination and you feel well; it’s not too likely that you have any of those conditions.

You could have dependent edema. Edema is the medical word for swelling. Dependent edema indicates that gravity is responsible for too much fluid finding its way into the feet and ankles.

During the day, when sitting or standing for a long time, gravity keeps blood in the legs and feet. Again, pressure in capillaries rises, and fluid oozes out from them.

Throughout the day, when you sit, prop your feet up — the higher the better. If you can take some time – about 15 to 30 minutes – to lie down with your legs elevated above heart level, that empties the legs of blood and stops the oozing of fluid into the feet and ankles. Elastic stockings compress tissues, which forces tissue fluid back into the circulation. Cut back on your salt use. Salt causes fluid retention and promotes ankle and foot swelling.

The booklet on edema and lymphedema discusses the causes of ankle swelling and their treatments. Readers can order a copy by writing: Dr. Donohue – No. 106, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6.75 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: About six months ago, I was hospitalized for pneumonia. At that time, my blood sugar was checked, and it was high. The doctor put me on diabetes medicines and a diabetic diet. I have been very careful about the diet, and I have lost 30 pounds since my discharge from the hospital.

For the past month, my blood sugar levels have been normal. The doctor stopped my medicine. My sister claims that stopping diabetes medicine is dangerous. Do you think I am in any danger? – D.S.

ANSWER: You’re not in any danger if your blood sugar stays normal.

The 30-pound weight loss could have removed your “diabetes” label. People who become diabetics later in life generally make insulin, but they don’t respond normally to it. Fat interferes with insulin action. Shedding body fat could have made you more responsive to your own insulin, and that would have brought your blood sugar levels down.

If that is the case, then you don’t need diabetes medicines. All you have to do is continue to test your blood sugar for a while and report to the doctor if it begins to rise.

DEAR DR. DONOHUE: What’s the difference between man-made vitamin C and natural vitamin C? A friend sells vitamins and considers herself an expert in the field. She says I should take only natural vitamin C, the kind she sells. Is there any good reason why this is so?

Is it true that smokers need more vitamin C than nonsmokers? I smoke. – E.C.

ANSWER: I don’t know of any evidence that supports the claim that natural vitamin C is more effective than the vitamin C made in a laboratory.

Smokers have lower blood levels of the vitamin than do nonsmokers. The suggestion has been made that smokers take an extra 35 mg a day. The recommended daily allowance for vitamin C is 75 mg for adult women and 90 mg for adult men.

DEAR DR. DONOHUE: What kind of speed makes walking beneficial? – B.S.

ANSWER: Brisk walking is walking a mile in 17 minutes. If a person cannot walk that fast, then any speed is better than sitting.

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.