"The premise is that going to a doctor is expensive, but you pay for what you get," says Donne’ Hamilton, RN, at Texoma Medical Center.

You can buy all kinds of tests Online. The ads say they'll test for pregnancy, drug use, HIV or hepatitis and many other things. Some have been approved by the Food and Drug Administration. Others have not.

“Can you really validate this?” Hamilton asks. “Do you know that a physician who is qualified to make those diagnoses is at the other end of the mouse pad?"

Here's the downside. Most of these tests need confirmation from a second, more sophisticated lab test. So the test might say you have a disease when you really don't!

"If it's strictly a PO Box, they don't have any information on a building or services, those raise red flags,” she says.

Avoid any site that promotes a new or miracle cure. Beware of claims that a test complies with all regulatory agencies. Check that out for yourself before buying.

"Look for the FDA approval and validate it,” Hamilton says.

If you still want to use a home diagnostic test, check it out first with the FDA. You can call them at 1-888-INFO-FDA or 1-888-463-6332. They’ll tell you whether the test is approved for use.