Before filling one of these tubes with blood for a cholesterol test, you're supposed to keep your stomach empty. But that may not be necessary. Nancy Louie/iStockphoto.com hide caption

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If there's a test for it, chances are a storefront lab is eager to help you have it done. iStockphoto.com hide caption

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U.S. Navy doctors Lt. Cmdr Ralph Pickard (left) and Ens. Jesse Rohloff study a patient's mammogram images at the National Naval Medical Center in Bethesda, Md. CWO4 Seth Rossman/U.S. Navy hide caption

itoggle caption CWO4 Seth Rossman/U.S. Navy