When there's a medical emergency, the last thing you’re probably thinking about is whether your insurance will cover an ambulance ride. Nor should you. An ambulance can get you to an ER fast, and the staff onboard can provide lifesaving care en route.

But you could get hit with a big bill if your insurer says the ride wasn’t medically necessary or if you’re picked up by an ambulance not in your insurer’s network. So you need to know when to call 911.

A dispatcher will send a ground ambulance plus first responders. You could get an even bigger bill if paramedics on the scene decide you need to get faster treatment and call for an air ambulance, which costs an average of more than $30,000.

Insurers may cover only a fraction of that bill even if it gets you to the hospital faster. But that’s not always the case. Leaving in the ground ambulance gives you a head start on an air ambulance, which first must be summoned and its crew readied, and then could be delayed while it looks for a safe place to land.

What to Weigh Before Making the Call

Even if you’re taken by ground ambulance, you may have to foot some of the cost. Dispatchers usually send the closest available ambulance, which might not be on your list of providers. And your insurer could refuse to pay if it deems the ride unnecessary. An ambulance is clearly justified if you or someone you’re with is unconscious, bleeding heavily, can’t breathe, or can’t be transported safely any other way. To be certain, check your insurer’s “emergency services benefits" coverage.

If you don’t think your situation is a real emergency, and you or someone you’re with can drive safely, don’t call an ambulance. And if you get stuck with a big bill, find out out to fight it and share your story at Consumer Reports’ End Surprise Medical Bills site.

Editor's Note: This article also appeared in the May 2017 issue of Consumer Reports magazine.