Are we talking legally, philosophically, work duties, training or what?
Training for a nurse is much shorter than training for a doctor; I think we all know that. I became a nurse after a 2 year Associate in Applied Science degree (which required another 2 years of prerequisites, but they still consider it a 2 year degree.) Some (probably most, these days) nurses have a Bachelor’s Degree, but their nursing license and what they can do is identical to mine. We’re encouraged these days to get Master’s Degrees, at which point many, but not all, of us become Advanced Practice Nurses.
Legally, a doctor and an advanced practice nurse (“nurse practitioner”) can make MEDICAL diagnoses, while a Registered Nurse can make NURSING diagnoses. We spend a lot of time in nursing school learning the difference and beating medical diagnoses *out *of student’s brains. 
Medical Diagnosis: Asthma
Possible Nursing Diagnoses we might see if someone is having an Asthma attack: Ineffective Airway Clearance, Impaired Gas Exchange, Ineffective Breathing Pattern, Fatigue, Activity Intolerance, Anxiety.
If a person isn’t currently having an asthma attack, but has in the past and is likely to in the future, we can put “Risk For” in front of any of those: “Risk For Ineffective Airway Clearance”. This isn’t just any old jargon, it has to be specifically approved and formulated jargon approved by NANDA, The North American Nursing Diagnosis Association. It’s based on very specific observations, signs and symptoms gathered during the nursing assessment process.
Generally speaking, you need the Medical Diagnosis for billing. Nurses use the Nursing Diagnosis to develop a Care Plan, but we can’t bill under Nursing Diagnoses.
Philosophically, it’s a tricky thing to generalize. GENERALLY speaking, doctors treat diseases, while nurses treat patients. That’s pithy, but not entirely accurate. Still, it does sum up the idea that doctors tend to focus on what’s wrong with the patient and how to treat the disease process, while nurses tend to take a gestalt view - not just the disease, but the environment, the family dynamics, the diet, activity, the mind, body, and (for lack of a better term) spirit of the patient. We’re interested in not only what’s wrong now, but what could go wrong down the road (those “at risk for” diagnoses.)
A doctor is needed to identify that a patient needs a cast for a broken leg and to order physical therapy. A nurse is going to want to know how many stairs are in your home, what you do for a living, if you’ve got adequate child care while you heal, how to relieve the itching from the cast and teach you nonpharmeceutical pain relief techniques, as well as make sure you know how to take your medicine, when, why and what you need to know to take it safely. She may teach you how to use those crutches (at least until you can see your physical therapist.)
Some of this is specific to the kind of nursing you’re talking about. A nurse in a dermatologist’s office is sometimes not much more than a receptionist and a hander-of-instruments during procedures. A hospital nurse on a med-surg floor is often a medicine-passer-outer and does a lot of “charting” in the computer tracking the patient’s condition each shift.
In my particular line of nursing (home health care) I have to be very independent, and my work is much more like what we learned of nursing in school - the work of an independent professional. While I need to have a physician’s order for nearly everything I do, the practical matter is that I visit the patient, figure out what he needs, then I write the orders, call the doctor and say, “here’s what I suggest”. She says, “Sure, sounds good, FAX it to me and I’ll sign it.” Or, much more rarely, she says, “Hmm…how about three visits a week instead of two?” or makes other suggestions, and I make the appropriate changes before I FAX her the order for signing. And that’s the best doctors. Many of them don’t even want to talk to me, and just have their receptionist or nurse tell me to FAX the orders and they’ll sign them, so I never actually talk to them. So while, on paper, I’m “following the doctor’s orders”, in reality, I’m actually calling the shots - although the doctor has to agree to sign.
Home health nurses are often the ones who do the care coordination (in the hospital and in a few home health companies I’ve heard of, this is often done by a medical social worker, but sometimes by a different nurse). I’m the one who calls the Physical Therapist to see how their visits are going and if we need to get an order to continue PT, for example. I make sure supplies the patient needs are ordered (although we have another person to do the actual ordering with the medical supply company, I have to tell him what the patient needs and get the doctor to sign the order for it.) I contact the doctor at least once every 60 Days to let her know how the patient is doing and if we need to continue home health or not, and get a new set of orders to her for signing.
I also do hands on care and teaching. I show people how to give themselves insulin or other shots, how to run IV’s and work their feeding tubes and pumps. I do wound care, changing dressings and cleaning out wounds. I do a LOT of teaching. Tons. That’s probably my biggest job - teaching people about their health condition, what it means, how it’s diagnosed, what to do about it and how to slow or reverse the progression of the disease. I teach caregivers and family members, as well as the person who is the patient.
This is what a GOOD nurse does. That is, I’m good for a new nurse, as evidenced by better than average patient outcomes and doctors and patients alike who request me by name and recommend me to other patients. I’m still learning, and hope to get better. There are also BAD nurses, who come, take vitals and push a piece of paper at the patient to be signed and then leave. We hates them, we does, precious. They gives us a bad name. :mad:
I hope this helps a little. I’m afraid I can’t be as specific about doctors, because one of the drawbacks of my line of nursing is that I don’t see them very much. They’re voices on the phone and signatures on the FAX to me, by and large. 