23andMe can finally tell you if you're at a higher risk for diseases like Alzheimer's - here's what you should know first

As of April 6, anyone who buys a $199 spit-in-a-tube genetics test from 23andMe will automatically learn if they're at an increased risk for developing certain diseases including Parkinson's and late-onset Alzheimer's.

Until then, the only way to get these kinds of results involved seeing a specialist (and, often, a genetics counselor).

But how much can you really learn from one of these tests? We spoke with Robert Klitzman, a bioethicist and psychiatry professor at Columbia University and the author of the recent book "Am I My Genes?" to find out.