If you are traveling to the US for medical treatment, you may need to bring additional documents at your interview, including:
A medical diagnosis from a local physician, providing information about your ailment and the reason you need treatment in the US
A letter from a medical facility or physician or in the US, stating they are willing to treat your ailment and estimating the projected overall cost of treatment and length of treatment.
Evidence that your medical and living expenses in the US, along with your transportation costs, will be covered. This may include income and saving statements, certified copies of an income tax return for yourself, another person or an organization that is paying for your treatment.