If you are going to prove a malpractice case, you need to be able to prove that the doctor did not meet the standard of care. The actions that are considered reasonable will vary depending on the type of healthcare professional and the particular community. So if you saw a general practitioner in a rural and medically underserved community, you won't be able to hold that doctor to the same standard of care as you would a highly specialized physician in a large community with state of the art medical tests and facilities available. This doctor will need to say that the course of action taken by your doctor was unreasonable under the circumstances. You should be prepared to have a difficult time finding a doctor to do this for you.
Most doctors are reluctant to testify against a colleague in a malpractice case.
Even if you are able to prove that the doctor treated you with substandard care, you will still need to prove that it caused injuries or damages to you. This may seem like a no-brainer, but chances are you weren't in perfect health before you saw the doctor. You are going to need to be able to prove that your medical outcome would probably have been different if not for the substandard care, not just that it might have been different. Once you have done all that, you will need to prove to what extent your injuries are greater because of the substandard care. For example, if you were in the hospital for a month, you'll need to prove that your hospital stay would have only been 2 days if not for the malpractice.