Method: 135 patients will be consented; 45 to the RA arm, 45 to an AITD arm, and 45 to a control arm. Exclusion criteria will filter patients who would have other reasons for altered vitamin B12 absorption, such as inflammatory bowel disease, surgery, or medication use. After obtaining consent subjects will be sent to lab a serum anti-GPC Ab test (obtainable in an SLE panel), RF, B12/folate (as available for ordering in CHCS), methyl malonic acid, and (for the control arm subjects and AITD subjects) an anti-CCP IgG. Patients will also complete a one-sided, one page questionnaire asking them about dietary and medication exposures.