No one regulates the accuracy of most of those tests, even though mistakes can be life-altering. At least one cautionary tale reaffirms the need for stricter guidelines.
When Nancy Seeger of Chicago lost her mother and aunt to breast cancer, she decided to undergo genetic testing to see if she also was susceptible to the disease. Her results indicated that she was not susceptible to breast cancer but to ovarian cancer.
After consulting with her doctor, she decided to have her ovaries removed. Eight months later, she was told that the out-of-state lab had made a mistake.
The Food and Drug Administration, which oversees most medical tests, says it lacks the money to regulate gene tests such as the one Seeger took. Nor does a federal law that oversees the quality and expertise of medical laboratories address genetics.
Experts say that while most laboratories do a good job, Seeger's experience illustrates risks that the public and doctors must understand.
Nor is she alone: Johns Hopkins University had to stop a study of inherited colon cancer last year after discovering a gene test bought from a commercial laboratory missed cancer-causing mutations in too many patients.
Now Health and Human Services Secretary Donna Shalala has appointed a panel of leading geneticists to determine, by Dec. 1, how to ensure quality gene testing.
But Dr. Tom Frank, Medical Director of Myriad Genetic Laboratories in Salt Lake City, Utah, says genetic testing for breast cancer offers people a choice to prepare for the real risks those who inherit the genes face.
"There is nothing in the environment that can do more than double risks. These genes increase a woman's risk ten times," he says.
But he acknowledges that they are not perfect.
"There are no medical tests that will tell you that you are definitely going to get something," said Frank. "If I told you that your risk of getting into a car accident is 85 percent, then you may take the train."
"I am talking about choices. Getting tested was the right thing for Nancy Seeger to do but the lab gave her the wrong results. The lab screwed it up."
His own lab - which is not the one Seeger used - has strict safeguards in place and has not made any mistakes, Frank says.
But many doctors, never trained in genetics, don't understand test results: A New England Journal of Medicine study found doctors misinterpreted results for almost one-third of patients tested for a certain colon cancer gene. Fortunately for the patients, the gene-testing lab intervened and provided the right information.
The FDA does regulate special "gene test kits" sold to doctors by a handful of companies. For example, some women with aggressive breast cancer are prescribeHerceptin only if an FDA-approved test kit shows the Her-2 gene the drug targets is fueling their tumor.
But the FDA isn't regulating the vast majority of genetic tests, those performed by laboratories or companies shipped a patient's blood.
Glenn McGee, a professor of bioethics at the University of Pennsylvania says that while genetic testing can be "an incredibly helpful aid," it needs regulation.
"If anyone wanted to set up a lab where they wash their hands and use instruments correctly, then they can say anything they want because the FDA calls it a 'homebrew' and 'homebrews' are not regulated," McGee told CBS News. "All kinds of people are setting up genetic testing of dubious validity."