If you don't have any health insurance, you can still get medical treatment after a serious car accident.  Some doctors are willing to work on something called a "lien" which means the doctor is willing to provide you with treatment so long as you promise to pay the doctor at the end of your case.
Usually, your attorney will be involved because most doctors aren't willing to make this arrangement unless you have a lawyer representing you.  You will have to sign something called a "lien form" and your lawyer will also sign.  Keep in mind, usually your doctor's bills will be paid out of the settlement proceeds from the accident.  However, it's important to be mindful of your expenses nevertheless because you don't want to dig a hole that's too deep to get out of.  For example, if you incur $10,000 in medical bills but the other party wasn't insured or only had the minimum required insurance policy, then you may be in trouble. 
Also, keep in mind that in most cases, the doctors expect to be paid regardless of the outcome of your case.  Therefore, if you lose the case or choose not to pursue it further for one reason or another, your doctor can technically force you to pay.  Some doctors routinely take their personal injury patients to small claims court to recover on bills. Don't be fooled that personal injury case only have an upside...that you can't lose.  A good lawyer should be able to guide you when it comes to these kinds of decisions.  If you need an experience personal injury lawyer in the Santa Clarita, CA area, please call my office for a free consultation.  In most cases, it's better to act sooner than later.