DEAR DR. DONOHUE: I am a 76-year-old female. Until December 2005, I thought I was in fairly decent health. That’s when I suffered a fractured hip. I didn’t fall, just sort of slipped down. I have recovered and feel great, and I exercise. Last April, my doctor prescribed 50,000 IU vitamin D once a week. I have been taking it ever since. I get lots of sun. I also take 600 mg of calcium with 200 IU vitamin D twice a day. And I take one multivitamin a day, a Centrum Silver. My doctor wants me to consider taking Fosamax. What’s going on? I worry about getting too much vitamin D. How does a person know how much is too much? – T.W.

ANSWER: Most adults get too little vitamin D. The official recommendation for daily vitamin D intake is 200 IU for those from 19 to 50, 400 IU for those between 51 and 70, and 600 IU for those 71 and older. Many experts believe these recommendations are insufficient and that the daily dose should be 800 IU to 1,000 IU. Vitamin D enhances calcium absorption and plays a critical role, therefore, in keeping bones strong and in preventing fractures. There are hints that vitamin D prevents osteoarthritis, lessens the risk of prostate cancer and helps prevent diabetes and heart disease. Time will tell if all this is true. The stuff about bones is true.

We get vitamin D when sunlight strikes the skin. It turns a substance in the skin known as a “provitamin” into vitamin D. Ten minutes of sunlight on the face and arms, three times a week to daily, is all the sunlight needed for this conversion. Older people’s skin is not so efficient in making the vitamin, and those living in northern latitudes can’t depend on sunlight conversion in the winter months.

From your weekly 50,000 IU tablet, you get about 7,000 IU of the vitamin daily. Centrum Silver has 500 IU. You get another 400 IU with your daily calcium tablets. So your daily intake is around 8,000 IU. Too much vitamin D can be a problem. It can damage the kidneys and can actually draw calcium from the bones. The upper daily limit is set at 10,000 IU. You haven’t crossed the border, but you’re in its neighborhood. The 50,000 IU tablet can correct a vitamin D deficiency in six to eight weeks. I’d say you’ve made that correction. Ask your doctor about stopping this high-dose vitamin therapy. If there is a question about the adequacy of your body store of vitamin D, a blood test can determine if it is too low, too high or just right.

DEAR DR. DONOHUE: Our 21-year-old daughter has been diagnosed with peripheral neuropathy. Her finger turned a shade of blue. She went to the emergency room and got the diagnosis there. What kind of doctor should we consult to determine if this is her condition? – V.C.

ANSWER: Your family doesn’t have a history of having peripheral neuropathy, right? So let’s remove all the genetic causes of it from consideration.

Twenty-one is young to come down with it. It’s more of an older person’s illness. People with diabetes and a few other diseases also are targets for it, but your daughter is in otherwise good health.

A blue finger isn’t a usual sign. Your daughter should see a neurologist or a vascular specialist to confirm this diagnosis, which appears a bit strange to me.

DEAR DR. DONOHUE: Will you please tell me what causes hand-foot-and-mouth disease? What can be done to prevent kids from getting it? – A worried grandmother of four grandchildren

ANSWER: Hand-foot-and-mouth disease is a viral illness most often occurring in children younger than 10. The virus’s name is coxsackie virus, from the name of the New York city where it was first found. It causes tiny blisters on the tongue, in the throat and on the palate, gums and lips. The blisters break to form shallow sores. The hands, fingers, feet and groin can also break out. The illness peaks in summer or early fall. It’s usually a mild illness that’s over in one week. There is no prevention for it, and there is no medicine for it.

DEAR DR. DONOHUE: What can you tell me about polycythemia? My doctor thinks I have it. I feel great, but I had some lab work done in preparation for a physical exam, and the doctor called to tell me about my blood count. I’m afraid to keep the follow-up appointment. Is this cancer? – R.R.

ANSWER: Polycythemia isn’t cancer. It’s too many red blood cells (and white blood cells and platelets). The bone marrow shifts into high gear in its production of these cells. Headache, dizziness, fatigue and bleeding are some of its symptoms.

If you do have polycythemia, treatment is quite straightforward: remove the excessive number of blood cells by removing blood.

If need be, there are medicines for treatment too. Hydroxyurea is one.

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.