A hereditary condition can increase the risk of forming calcium oxalate stones. Intestinal resection, parathyroidism, and other more rare conditions also may cause renal calculi, and dietary factors can increase or reduce the risk of forming kidney stones. A low-oxalate diet is often prescribed for people who have increased levels of oxalic acid in their urine or who have a history of forming kidney stones. A treatment program including a low-oxalate diet and plenty of fluids reduces the risk of stone formation. A low oxalate diet is not always effective in reducing urinary oxalic acid levels because most oxalate found in urine is made in the body and does not come from the diet. People with a predisposition to stones are also encouraged to drink plenty of fluids (3 to 4 quarts [liters] per day), limit sodium intake, and consume adequate calcium, although calcium supplements should not be taken between meals.