The 23andMe kit.
The 23andMe kit. - 
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Nearly half a million people have put their spit into a little tube in the last six years and sent that tube to a company called 23andMe. The company then genetically analyzes that saliva. The results are supposed to show customers how susceptible they are to more than 250 diseases. But the FDA now says the company hasn't proved the tests are accurate enough, and the agency is worried Americans are relying on the results instead of going to the doctor.

Dov Fox specializes in medical ethics at the University of San Diego School of Law. He says the FDA has given the company an ultimatum.

"This field of personalized medicine is really in its infancy, and its terrifically exciting what we might learn one day, but we're not there yet.  23andMe hasn't shown that their reports about your health from your genes alone are all that useful. They're just not accurate at this time in the way that the FDA requires."

Follow Lizzie O'Leary at @lizzieohreally