There is a fine line between being an educated patient advocate, and being a know-it-all family member who is in the medical field.
Medicine is such a broad and rapidly changing science. As such, it is impossible to keep up to date with all the new developments. New drugs are developed and approved every year. Studies either confirm or debunk old notions. Guidelines are revised based on these new developments. This rapid expansion in our knowledge is part of the reason physicians have been specializing and sub-specializing.
It is not unusual for me to have patients who have family members who are in the medical field; as physicians, nurses, and nurse practitioners. In some ways, it makes it easier to explain the patient's diagnosis and the treatment plan. On the other hand, a little knowledge is a dangerous thing, and there are some physicians or other healthcare workers who feel that they remember enough from medical school to know about what I do every day. I don't mind an active academic discussion, but it does become a problem when well-meaning family members either try to convince me to change a treatment plan or (worse) change it themselves. I've had patients come back on a completely different set of medications and when I ask them how it happened, they say, "Oh, my cousin who is a cardiologist, told me this would be better." Which would be fine if the patient were actually better, but invariably, they are not. And when I say, "Then why isn't Cousin Frank treating you?" The reply is: "But you're my doctor!"
Now, I have recently been on the other side of this situation. A relative is in the hospital and is on a specialized floor. She has what is usually pretty well-controlled diabetes, but due to her current illness, her blood sugars have been high. And, she was not being managed appropriately. I have faith that the specialists seeing her are excellent at what they do, but what they do is not diabetes. I happened to be present when they did rounds one day. I introduced myself, said I am an endocrinologist and mentioned that I did not feel she was getting the necessary care for her diabetes. They said they would address it. I later learned that their method of "addressing it" does not meet with what is considered standard of care in 2014. I am in another state, and I felt unable to help negotiate better care for her. One of our other relatives, on the other hand, was there all the time and was a strong advocate for the patient. Apparently, they later requested an endocrine consult.
There is a fine line between being an educated patient advocate, and being a "PIA" know-it-all family member. I think that the line gets drawn where one's expertise ends - whether it's the treating physician or the family.