So you went in to the hospital, and you didn't get the results you were after. Maybe you were hoping they could fix an infection in your leg, but it had to be amputated, or perhaps you were hoping your cancer would be cured, when it persisted in spite of the treatments. Does this automatically mean you have a medical malpractice case?
It does not. It's very important to remember that "bad" outcomes do happen. Hospitals are not always able to give you the optimal outcome, even when doctors do all in their power to get you there. Simply not experiencing the results you were after is not grounds for a lawsuit on its own.
However, you may be able to start a lawsuit if negligence was involved. This negligence could mean that the typical standard of care was not met. Since you received sub-standard care and also had a negative outcome, then you might be able to sue.
For instance, if the doctor operating on your leg used the wrong procedure, allowing the infection to spread, and that's why you needed to have it amputated -- when using the right procedure would have removed the infection and allowed you to keep your leg -- then the evidence could be in your favor. You can argue that the doctor's mistake is really what led to the amputation, which wouldn't have happened had you gone to a different medical center and been given proper treatment.
Were you injured due to negligence in the hospital, and do you feel that the standard of care you had expected wasn't met? If so, it may be time to look into compensation for your medical costs, future costs due to new issues, pain and suffering and more.
Source: Forbes, "10 Things You Want To Know About Medical Malpractice," Demetrius Cheeks, accessed Oct. 12, 2016