A couple of months ago, I was diagnosed with congestive heart failure. I took the tests the doctor ordered, and he said he would see me again in a couple of months. He doesn't appear to be too concerned. I feel pretty good most of the time, but sometimes I am short of breath, and I don't have the energy I once had. I am 81 years old, 5 feet 7 inches tall and weigh 165 pounds.

Should I be engaged in a moderate exercise program? What kind of exercise? How often? Can I do exercises with light weights? — J.B.

Answer: Thank you for asking. Things are going well for me. I hope they are with you, too.

Congestive heart failure, or simply heart failure, indicates that the heart pumps too weakly to supply the body with the blood and oxygen it needs. Because of the weak pumping action, blood backs up into the lungs and "congests" them. That congestion leads to shortness of breath, particularly when a person is active. Blood also backs up into the body's blood vessels and congests them. Fluid leaks out of the circulation and swells the ankles and feet. Heart failure's other major symptom is fatigue, a sign the body isn't getting the oxygen it needs.

The medicine treatments you're getting (included in an edited part of the letter) are standard for heart failure. The medicines lessen the burden on the heart by lowering blood pressure, slowing the heart's beating and getting rid of retained body fluid. Losing excess weight and restricting salt use are two other aspects of treatment. People with congestive heart failure should weigh themselves daily. Weight gain often is fluid gain, especially when it's rapid weight gain. It tells you that you're not watching your salt intake or that you need to increase the dose of your medicines. You should report such weight changes to your doctor.

Exercise is recommended for all with congestive heart failure. The specifics of the exercise have to be prescribed by your doctor, just as the doctor prescribes medicine. Walking is usually tolerated well. Lifting weights is an approved exercise. But you have to know your limits, and your doctor is the one to set them.

The booklet on congestive heart failure deals with it and its treatments. Readers can obtain a copy by writing: Dr. Donohue — No. 103, 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: I recently was diagnosed with a vitamin D deficiency. I am concerned about the condition of my bones, and wonder how long this has been taking place. I am now on 50,000 IU of vitamin D weekly. What caused this deficiency? I thought my calcium was taking care of me. — S.W.

Answer: If your blood calcium level is also low, that is evidence that your deficiency was longstanding. Calcium absorption is dependent on having enough vitamin D.

Lots of older people are deficient in this vitamin. Sunlight transforms a vitamin D precursor in the skin into the active vitamin. Many older people don't get enough sunshine to affect this transformation, especially older, homebound people. And all those who live in the northern half of the U.S. and all of Canada get too little sunshine in the winter to keep their vitamin D levels normal. Adults have to pay attention to getting enough of this vitamin by eating foods fortified with it (cereals and dairy products) or by taking a vitamin D supplement. Your treatment is standard one, and now, with the addition of vitamin D to your program, you are protecting your bones.

Dear Dr. Donohue: I am hypothyroid (produce too little thyroid hormone). I have been this way for 20 years and take thyroid medicine. I was told I would take it for the rest of my life. A TV celebrity and her doctor told the whole world that she no longer has to take thyroid medicine. Can you stop taking thyroid medicine? — D.S.

Answer: Replacing thyroid hormone because the thyroid gland no longer makes enough of it is usually a lifetime affair. Stopping medicine for an overactive gland, however, is quite possible.