Q. If I have health and car insurance, won’t that cover me and my passengers if I get hit by an uninsured driver?

A. Your health insurance will cover you, minus any deductibles, but it won’t cover your passengers if you get hit by an uninsured or underinsured motorist. Your auto-liability coverage will pay for any damage you cause, but it may not pay for your injuries or those of your passengers if the other driver was at fault.

You can’t rely on your passengers having their own health insurance, either. That’s why something called uninsured or underinsured motorist coverage (or UM/UIM, as it’s known in the business) exists: to stand in place of the other guy’s missing or insufficient liability coverage. It has no deductibles. About 13 percent of all drivers in the U.S. are uninsured, so we recommend that you buy UM/UIM coverage with the same limits as your own liability insurance.

For more auto insurance advice, read our investigative report, "The Truth About Car Insurance," and find the top car insurance companies that won't break the budget.

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Editor's Note: This article also appeared in the December 2015 issue of Consumer Reports magazine.