A fasting B12, or ā??Schilling test,ā? looks at how well B12 is absorbed by the body. The patient fasts overnight and then has a vitamin B12 injection and takes radioactive-labeled vitamin B12 tablets. The amount of vitamin B12 that comes out in the urine is measured. B12 and folate deficiencies can cause certain types of anemia or neurological symptoms such as neuropathy.

The doctor may have also ordered fasting blood-glucose testing, too, to check for diabetes, which can also cause neuropathy (but usually only after someoneā??s been diabetic for a long time).

The ANA test is an antinuclear antibody blood test that can detect certain autoimmune diseases such as rheumatoid arthritis or lupus.

A GM1 glanglioside test looks at the level of anti-ganglioside antibodies (AGA) to GM1 ganglioside in patients who have motor neuropathies.

IgG and IgM (along with IgA) are other types of immunoglobulin antibodies that show up in bloodwork when people have some sort of autoimmune disease or sometimes also other types of blood-related disease.

I was able to find out all this testing info on my school research sites. I'm not trained yet in what they're all used for, but it sounds like the doctor who ordered those tests was trying to nail down the cause of any neuropathy and rule out a vitamin deficiency or possible diabetes, then see if he could determine whether an autoimmune disease process such as rheumatoid arthritis or lupus was causing your friend's neuropathy.