What was her kidney function like on release from the hospital? What did they do with her medications while she was in the hospital? Who are the survivors -- husband, adult children? To what did the doctor attribute her death? There are a number of factors here which bear examining by a qualified attorney.
I agree with Mr. Curtin. There are many unanswered questions, the answers to which would affect the strength of any potential claim. You should speak with a lawyer.
Your claim is probably governed by one or more limitations periods. This means that you must take certain actions within a certain period of time to preserve all of your rights. A limitations period can be very short. I encourage you to speak with a lawyer who handles medical negligence cases in your area as soon as possible. I would be happy to help you find someone.
A medical malpractice lawyer would need to order her medical records and send them to an expert to review to ascertain whether there was a breach of the standard of care.
You did not indicate where she was take from... nursing home??? private residence???. Also, as others have pointed out, is this your mother, spouse, what relationship. You may have a case, but see a local attorney, because every state is different in terms of who can sue, and how long you have. The other attorneys have given you good advice, since we don't know what the baseline creatinine and BUN's were which are the lab test reflective of kidney failure.
A death certificate listing the cause of death and a medical examiners report will be critical in your case. You will then need to consult with a toxicologist who can interpret the levels of the medication and give you an idea of how far above a therapuetic dose each of the medicines were. Cases of this type are complicated.