Even if you are on a bicycle or were a pedestrian, your auto insurance personal injury protection (PIP) should pay your medical expenses if you are struck by a motor vehicle.

If you do not have auto insurance and do not have health insurance, than the other driver’s insurance should pay your medical bills. 

Your insurance company is required to pay all of your medical expenses within the first year that are reasonable and related to the accident, up to your policy limit ($15,000 for most people).

This does not mean that your auto insurance company, or the driver's auto insurance will pay these bills.

In my own experience, even when a bicyclist was seriously injured and with a witness, they still too often have to fight for a fair insurance coverage claim. As reported in Portland's Willamette Weekly Newspaper, A horrific crash and a potential mayoral candidate's company:

The impact smashed Luikart's upper jaw, broke her left shoulder, fractured her right wrist and left her with severe dental injuries. But Luikart's attorney, Michael Colbach, says New Seasons' insurer refused to pay. Instead, Colbach says, New Seasons blamed the accident on Luikart, who has no memory of the crash. The lone eyewitness of the crash said Luikart was not at fault, and the jury agreed.

Or, when a bicyclist was doored by an Uber driver in Portland, the murky insurance situation of a gig driver added to the doored bicyclist's troubles in getting the personal injury protection and liability insurance coverage he was entitled to, as reported by The Oregonian newspaper, Cyclist sues after Uber, private insurance fail to cover crash:

Pavenko was cited for improper opening of a door. He has pleaded not guilty, according to court records. [...] Police recorded Pavenko's personal auto insurance information, but Root's attorney, Michael Colbach, said Pavenko's insurer wouldn't cover the liability because Pavenko was driving for hire at the time.

Insurance companies do not pay bills if they don't have to and the insurance company may deny your medical bills.

I am actively trying personal injury cases and as long as insurance companies continue to try and cheat my clients, I intend to keep taking cases to trial.

For a Seattle bicycle attorney, at the time, an associate of Washington Bike Law, her own insurance company actually denied her auto insurance coverage existance and came up with surprising new intrepretations of what her auto insurance policy coverage meant! This attorney's story is one of eventual triumph through the justice system and the experienced legal representation she received from her employer at the time, Bob Anderton.

I am a bike lawyer. By this I mean that I represent injured bicyclists. I am also a bicyclist. Last year, I was hit by an uninsured driver on my ride home from work and utilized the Insurance Fair Conduct Act (RCW § 48.30.015) when my insurer claimed that I was not insured when riding my bike. The Insurance Fair Conduct Act (IFCA) was approved by voters and signed into law in 2007. IFCA provides remedies for people whose claims are unreasonably denied by their insurance companies or if their insurance companies fail to comply with particular regulations governing unfair claims settlement practices.

Stacie Bain, "Riding Along Uninsured with 'IFCA'"
King County Bar Bulletin, November 2009 (PDF)

Bob and Washington Bike Law won another important bicycle legal case in December, and in this case, the bicyclist's own insurance company was trying to fight paying the auto insurance coverage and personal injury protection arguing that a bicyclist was not a pedestrian in Washington state law. The bicyclist was doored and as Bob writes of the story, the liability insurance paid, it was the cyclist's own insurance company that fought paying for the personal injury protection the bicyclist paid for.

Talk to an experienced attorney if you have been injured in an auto accident on your bike or as a pedestrian as soon as you are able to.