If you simply want to understand or solve the daily needs and emergencies, then, age is not a problem, as long as you have the heart, when you can learn;
If you want to engage in the medical profession, it depends on the nature of what you want to engage in (work), for example, such as the treatment of general pathology, nursing, and health care, generally still can, but if it involves a large-scale But, if it involves large-scale surgery, especially to involve the use of high-end medical equipment, I recommend that you give up the idea of medicine, this is not all because of the age of the problem, but because, this kind of accumulation of knowledge, the need to have an absolutely formal education, and only formal education to have the corresponding conditions of supply of formal medical equipment to be learned, not by self-study, correspondence or simple internships can be learned.