A 75-year-old woman with diabetes presents with fatigue, pallor, poor balance, and a complaint of a "pins and needles" sensation of her hands and feet. On initial laboratory testing, you determine that she has a macrocytic anemia. How can you distinguish between alcoholism and folate deficiency? How can you distinguish between vitamin B12 deficiency and folate deficiency?  Name three medications and three medical or surgical causes of vitamin B12 deficiency. What is the most common neurologic finding and what is a classic neurologic finding of vitamin B12 deficiency?