I am a 34-year-old man with a family history of kidney stones (my father, mother and brother). Is there anything that can be done to reduce my risk of developing them? R.H., Haifa Dr. Andrew Sambell, a urologist at Baylor Medical Center in Texas, advises: Yes, there are things you can do. Drink four to eight glasses of water a day and twice as much in hot weather. Go easy on meat; a diet high in animal protein increases your risk. A vegetarian diet two days a week or cutting your meat intake by 30 percent is recommended. In addition, you should shake the salt habit. Most salt in our diets comes from prepared foods, not salt we add at the table. Fast food is typically high in salt, so you should avoid it if possible. Reduce your caffeine intake. If you drink mostly colas, coffee or iced tea, try to switch to decaffeinated beverages at least some of the time, as caffeine is a diuretic which can leave you dehydrated. Buy some lemons. Lemons are high in citrate, which acts as a stone inhibitor. Slice them up and put them in your water or tea. This also may make your water more palatable. There are a couple of uncontrollable factors that can increase your odds of kidney stones, including recurrent urinary tract infections, certain medical conditions and a family history. There also are some genetic risk factors that can increase your likelihood of getting kidney stones. If, in spite of your efforts, you get a kidney stone, it will probably pass on its own. "Most stones of four millimeters or less will pass. Anything larger than 6 millimeters won't pass on its own." But a large stone no longer necessarily means surgery: Extracorporeal shock wave lithotripsy (ESWL), which has been available for about two decades, uses sound waves to crush the stone into small particles that can pass on their own. There are also minimally invasive surgical techniques that doctors can use to remove kidney stones. Open surgery is necessary only in one to two percent of people with kidney stones. People with recurrent kidney stones should have their risk factors evaluated by a doctor, since multiple stones could lead to a complication. I am a 52-year-old man who was diagnosed two years ago with type II diabetes. My doctor prescribed metformin twice a day and my blood sugar level and my weight are under control. I read recently that taking metformin interferes with the body's absorption of vitamin B12 and that such diabetics should take Tribemin and other forms of the vitamin. My doctor never prescribed this. Should everyone who takes metformin take this vitamin supplement, or should one be tested for a deficiency first? What are the symptoms of vitamin B12 deficiency and what harm does it cause? D.N., Zichron Ya'acov Veteran diabetologist Prof. Menachem Shapiro of Kfar Saba's Meir Medical Center comments: Metformin may interfere with calcium metabolism and indirectly reduce vitamin B12 absorption because vitamin B12 absorption requires calcium. Studies show that between 10% to 30% of patients taking metformin have evidence of reduced vitamin B12 absorption. There is no accepted approach, however, to this question. I personally explain the risk to patients who take metformin and recommend that they also take vitamin B12 to avoid problems, even if the risk is quite small. The vitamin has no side effects, but if there is a serious deficiency, anemia, fatigue, loss of appetite, numbness in the hands and feet and even dementia could follow. Vitamin B12 is an important water-soluble vitamin. In contrast to other water-soluble vitamins, it is not excreted quickly in the urine, but rather accumulates and is stored in the liver, kidney and other body tissues. As a result, a vitamin B12 deficiency may not manifest itself until after five or six years of a diet supplying inadequate amounts. It works with folic acid in the synthesis of DNA and red blood cells and is vitally important in maintaining the health of the insulation sheath (myelin sheath) that surrounds nerve cells. The amount of vitamin B12 actually needed by the body is very small, probably only about two micrograms (2 millionths of a gram) per day. Unfortunately, vitamin B12 is not absorbed very well, so much larger amounts need to be supplied through the diet or supplementation. Fortunately, oral supplementation with vitamin B12 is safe, efficient and inexpensive. Rx For Readers welcomes queries from readers about medical problems. Experts will answer those we find most interesting. Write Rx For Readers, the Jerusalem Post, POB 81, Jerusalem 91000, fax your question to Judy Siegel-Itzkovich at (02) 538-9527, or e-mail it to firstname.lastname@example.org, giving your initials, age and residence.