[an email about bulimia and hair loss (author did not want question posted on Earth Clinic)]
If bulimia and hair loss, the condition seems to point to a severe vitamin B complex deficiency. As a result, I would get a good vitamin B50 taken once every day for a week or two, before taking it once every other day. A vitamin B50 contains most vitamin B of 50 mg each and some will be 50 mcg. I think the addition of B1 and B3 may be further helpful of 100 mg more each.
It should be noted that magnesium is synergistic with B6, such as magnesium citrate taken at 250 mg per day for 5 days out of a week.
Sometimes drinking soy milk once a day, high in manganese also reduce the hair loss.
If vomiting from bulimia, taking 1/2 teaspoon of baking soda in 1/2 glass of water may reduce the acidosis that may cause the body to rid of excess acid. By alkalizing the body will reduce the need to rid of acidosis as the baking soda will neutralize the acidity.