Don't assume you are being tested for B12 levels. Typically doctors ignore this. Low levels will impact the nerves and cause various dysfunctions of the nervous system including the autonomic (gastroparesis).

Here is a recent post with a link to Metformin induced low B12:
http://neurotalk.psychcentral.com/sh...ight=metformin

Get your numbers also from the doctor. Do not accept "normal"
since many lab ranges include 200's as "normal" which are not! (One should be at 400 or above.)

Some doctors believe if there is no anemia, then B12 does not need to be tested. This is just not true. Many people can have very low B12 levels and not show any signs of anemia, but may still have severe neurological problems. Some patients may show slightly elevated MCV values on CBCs before any frank anemia occurs. This too, is often ignored by doctors. (this test measures the size of the red blood cells, and when it increases can signal low B12 levels). Interpretation of test results is highly subjective and many doctors do not attend to things uniformly. So it is up the the patient in this case to be an active participant.

Since B12 is so simple to take, pennies a day, injections not necessary as oral works, it is a shame to neglect this. Some of our other posters on other boards like MG and MS also take B12. Just about all our posters on PN use it.

This article from 2000 illustrates confusion regarding lab results:
http://www.ars.usda.gov/is/pr/2000/000802.htm

And this medical paper from 2003 corrects the misperception:
http://www.aafp.org/afp/2003/0301/p979.html
Stomach acid is required to activate the intrinsic factor that transports B12 into the body. When stomach acid is gone, the only way oral B12 can get in is passively, absorbed in the small intestine. So very large doses of at least 1000mcg have to be given daily (sometimes more) to get the small amount that is actually absorbed (without the assistance of instrinsic factor).
It is best to take B12 orally on an empty stomach for this reason, so the microgram dose will not be lost in fiber from food.