• 1. Fatigue and/or weakness. Not just the feeling that we didn’t get enough sleep last night, but deep fatigue...or weakness where it’s hard to get through the day.
• 2. Weight loss plateau. When we don’t get enough protein, medical research indicates that the body tries to store calories rather than burning them.
• 3. Hair loss. We believe it is often preventable with enough protein.
• 4. Surgical complications. Is there surgery in your future? For many, the answer is yes. The best single numerical predictor of how well a surgery will go is your protein status. And, your body will heal slowly, sometimes very slowly, if your protein status is low.
• 5. Muscle Loss. When you don't get enough protein for weeks, you body starts taking protein from your muscles. So your body is actually taking muscle -- to help maintain other cells, and organs, and hormone levels. So it's possible you might be more easily injured if you regularly don't get enough protein.

These symptoms can also be caused by other things, so it is always good to ask your doctor. 

Article reprinted with permission (in it's entirety) from Unjury Medical Quality Protein