ROCHESTER, Minnesota: The Food and Drug Administration is asking doctors to immediately check patients who use fen-phen, the drug combination touted as a miracle diet pill, for heart valve problems after a Mayo clinic study showed a preliminary link between the drugs and a rare form of valve disease. The combination of fenfluramine and phentermine (fen-phen) is often used to treating alcoholism and cocaine addiction. But it's most popularly prescribed as a weight-loss pill. The Mayo study followed 24 women in their forties with no history of heart problems who developed a deterioration of their heart valves after taking fen-phen for six to 18 months. "This study raises a red flag that says this has to be looked into more closely," says TIME's Christine Gorman. "But it does not say the drug should be banned or that the link is definitive." One key question is dosage. Since several of the women examined were taking higher-than-prescribed doses, would the damage would have occurred in those who just followed the prescription? Wyeth-Ayerst Laboratories, the sole maker of fenfluramine and its cousin, Redux, argues that the study fails to take account of causes such as lifestyle and notes that it has never recommended that doctors combine fenfluramine with other weight loss drugs like phentermine. The real danger is that these side effects could kill people for whom the drug was never intended. While fen-phen is intended for people who are morbidly obese (individuals who weigh 30 percent more than average) women anxiously looking to lose a few extra pounds are also taking the drug. The obese are trading risks -- trying to escape a well-documented set of risks in heart disease, diabetes, kidney failure and stroke by taking a chance that the drug may expose them to heart valve problems. But fanatic dieters may be risking their lives for no good reason.