Medical malpractice is professional negligence by act or omission by a health care provider in which the treatment provided falls below the accepted standard of practice in the medical community and causes injury or death to the patient, with most cases involving medical error. You must show that you had a physician-patient relationship with the doctor you are suing -- this means you hired the doctor and the doctor agreed to be hired. For example, you can't sue a doctor you overheard giving advice at a cocktail party. If a doctor began seeing you and treating you, it is easy to prove a physician-patient relationship existed.
Just because you are unhappy with your treatment or results does not mean the doctor is liable for medical malpractice. The doctor must have been negligent in connection with your diagnosis or treatment. To sue for malpractice, you must be able to show that the doctor caused you harm in a way that a competent doctor, under the same circumstances, would not have. Because many malpractice cases involve patients that were already sick or injured, there is often a question of whether what the doctor did, negligent or not, actually caused the harm. For example, if a patient dies after treatment for lung cancer, and the doctor did do something negligent, it could be hard to prove that the doctor's negligence caused the death rather than the cancer.