In an ordinary personal injury action based on negligence, the plaintiff must prove among other things that the defendant owed the plaintiff a duty of care, and failed to uphold that duty. This means generally that the defendant must act as a "reasonable person" would under the same circumstances; what a reasonable person would do is up to the determination of the jury.
For some legal causes of action, though, the applicable standard of care can change to a higher level. Medical malpractice actions constitute one of these situations under which the ordinary reasonable person standard is not sufficient to establish negligence on the part of the defendant.
The reason for this different standard is simple: it is generally unreasonable to put jurors, many if not all of whom may have little or no training or experience in the medical profession, in the position of knowing what a competent physician would or would not have done in the circumstances that the plaintiff claims led to his or her injury. Instead, under South Carolina law the standard for the defendant's duty of care in a medical malpractice claim is "...that which would be exercised by competent practitioners in the defendant doctor's field of medicine."
In other words, whether a doctor can be found to have committed medical malpractice depends on what his or her peers would have done, instead of what a generic "reasonable person" would have.
Note that this medical malpractice standard of care is not based on the result of treatment. Even if the treatment is unsuccessful or leads to a bad result, as long as the defendant did not vary from what the standard of skill and care would be for other doctors faced with the same facts, then that standard is met.
Determining the medical standard of care requires that the plaintiff's legal counsel be able to identify and work with expert witnesses who can explain what that standard is in a given case and establish that the defendant failed to live up to it. This is something with regard to which you should seek the assistance of an experienced medical malpractice personal injury attorney.