Insurance companies are some of the largest corporate institutions with large budgets and compelling reasons to invest in prevention of fraud of all kinds - from insurance coverage to recovery of damages. This clearly applies to how a larger number of insurance companies handle injury claims today. The insurers invest resources into studying injury claims (especially the ones that are alleged to be serious) and among other things, determining with the help of highly qualified nurses and doctors whether the medical treatment an injured person received was "reasonable and necessary." These are magic words when it comes to proving damages in court or determining the settlement value of an injury case. 
An insurer who discovers that the claimant treated far longer and far more frequently than he likely should have, considering the injuries sustained, will look closely at the nature and the cost of treatment received. If the treatment is clearly excessive and more expensive than it should be, the insurance company will use that information to cast strong doubt on the claimant's credibility, making him/her look like someone who is trying to treat more than needed and inflate claims for the sheer purpose of increasing recovery. This argument works quite often to reduce a claimant's recovery or event lose the case in court where they otherwise could have won. This is because few factors hurt a party in trial in front of a jury than credibility issues. Once the jury determines or event suspects that the claimant treated more than he needed for improper reason, they likely will doubt the entire claim and won't believe much else of what the claimant has to say on the stand. This is exactly the reason why it's a good idea to avoid getting more medical care than you need for your injuries, especially if your case is likely to go to trial. 

You should especially make sure you don't get too much of the treatment that doesn't help you. Therefore, if for instance you treat for a chiropractor for 1-2 months and you feel no improvement in your pain symptoms, you should at least consider switching to physical therapy, acupuncture, etc. This is because it's usually quite hard to explain why a person went to see a particular doctor for 6 months or more several times a week if it didn't help at all. 

Two of the most common mistakes that I see people make after being involved in an injury auto accident or any other kind of accident, as far as medical treatment goes, is (1) overtreating and (2) not treating with an MD doctor. 

Overtreating means getting more treatment than you need or continuing to treat with the same healthcare professional for months even though you have been feeling for a while that the type of treatment you are receiving is ineffective. If you have been seeing a chiropractor for over four months, then you should at the very least ask him when he believes your treatment should be over and when you are expected to achieve maximum improvement. Generally, seeing a chiropractor for longer than six months will likely make both the insurance company (during settlement negotiations) and the jury (if your injury case goes to trial), look at your injuries with a greater skepticism. They will be asking why you didn't choose a more "serious" treatment, such as medication or surgery, if your injury was as bad as you make it sound.   

Seeing an M.D. will significantly affect the value of your injury case. You might find a chiropractor, a physical therapist, or even an acupuncturist to be effective in alleviating you pain, but you should still see an M.D. doctor at least once or twice. The first time should take place as soon after the accident as possible for general evaluation and referral to specialists, and at the end of your treatment, to see if you need any kind of other treatment and evaluation, if you still have pain symptoms, or if you developed a new kind of symptoms. For instance, if, since the injury, you started developing headaches or double vision, you should definitely report these issues to your doctor, who then might urge you to see a neurologist.    

To make sure you avoid other mistakes that would prevent you from obtaining a fair settlement for your injuries, you should consult with a personal injury lawyer to discuss your accident, your injuries and how you should go about handling your claim, whether you do it on your own, or whether you retain an attorney to represent you.