{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,9]],"date-time":"2026-06-09T08:45:54Z","timestamp":1780994754258,"version":"3.54.1"},"reference-count":18,"publisher":"SAGE Publications","issue":"11","license":[{"start":{"date-parts":[[2012,11,1]],"date-time":"2012-11-01T00:00:00Z","timestamp":1351728000000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.sagepub.com\/page\/policies\/text-and-data-mining-license"}],"content-domain":{"domain":["journals.sagepub.com"],"crossmark-restriction":true},"short-container-title":["Ann Pharmacother"],"published-print":{"date-parts":[[2012,11]]},"abstract":"\n BACKGROUND:<\/jats:title>\n \n Metformin can result in vitamin B\n 12<\/jats:sub>\n deficiency, potentially leading to complications such as neuropathy. Annual monitoring of vitamin B\n 12<\/jats:sub>\n has been suggested; however, it is unknown whether current practice reflects this recommendation.\n <\/jats:p>\n <\/jats:sec>\n \n OBJECTIVE:<\/jats:title>\n \n To identify vitamin B\n 12<\/jats:sub>\n monitoring patterns in patients on long-term, high-dose metformin. Secondary objective was to determine the frequency of new vitamin B\n 12<\/jats:sub>\n deficiency, anemia, and neuropathy documented after initiation of high-dose metformin.\n <\/jats:p>\n <\/jats:sec>\n \n METHODS:<\/jats:title>\n \n Electronic medical records of veterans treated at the Veterans Affairs Maryland Healthcare System with high-dose metformin (\u22652000 mg\/day) as of November 1, 2010, were reviewed. Data regarding metformin treatment, vitamin B\n 12<\/jats:sub>\n measurements, and documentation of vitamin B\n 12<\/jats:sub>\n deficiency, cyanocobalamin supplementation, anemia, and neuropathy were collected. Subjects treated with metformin for less than 1 year or those with documented peripheral neuropathy, megaloblastic anemia, vitamin B\n 12<\/jats:sub>\n deficiency, or a condition associated with vitamin B\n 12<\/jats:sub>\n malabsorption prior to metformin initiation were excluded.\n <\/jats:p>\n <\/jats:sec>\n \n RESULTS:<\/jats:title>\n \n Subjects (N = 235) had a mean metformin dose of 2050 mg\/day and mean duration of treatment of 5.2 years. Sixty percent did not have vitamin B\n 12<\/jats:sub>\n measured. Of subjects receiving metformin for 10 years or more, nearly half (46%) never had vitamin B\n 12<\/jats:sub>\n measured. New documentation of vitamin B\n 12<\/jats:sub>\n deficiency or cyanocobalamin supplementation was found in 5.5% of the population, and anemia was found in 12%. Of the 14% with new neuropathy, 42% did not have vitamin B\n 12<\/jats:sub>\n measured.\n <\/jats:p>\n <\/jats:sec>\n \n CONCLUSIONS:<\/jats:title>\n \n Vitamin B\n 12<\/jats:sub>\n was not routinely monitored in patients on high-dose metformin, even in those at highest risk (\u226510 years of therapy), or in those with potential manifestations of vitamin B\n 12<\/jats:sub>\n deficiency (neuropathy). Cases of vitamin B\n 12<\/jats:sub>\n deficiency and resulting anemia or neuropathy may be undiagnosed and untreated because of lack of monitoring. Prospective studies examining the effect of increased vitamin B\n 12<\/jats:sub>\n monitoring on identification and treatment of vitamin B\n 12<\/jats:sub>\n deficiency in patients on metformin are warranted.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.1345\/aph.1r223","type":"journal-article","created":{"date-parts":[[2012,11,1]],"date-time":"2012-11-01T00:31:44Z","timestamp":1351729904000},"page":"1470-1476","update-policy":"https:\/\/doi.org\/10.1177\/sage-journals-update-policy","source":"Crossref","is-referenced-by-count":26,"title":["Evaluation of Vitamin B\n 12<\/sub>\n Monitoring in a Veteran Population on Long-Term, High-Dose Metformin Therapy"],"prefix":"10.1177","volume":"46","author":[{"given":"Sarah A","family":"Pierce","sequence":"first","affiliation":[{"name":"Sarah A Pierce PharmD, PGY1 Pharmacy Practice Resident, VA Maryland Healthcare System\u2014Department of Pharmacy, Baltimore, MD"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Amy H","family":"Chung","sequence":"additional","affiliation":[{"name":"Amy H Chung PharmD, Clinical Pharmacy Specialist, VA Maryland Healthcare System\u2014Department of Pharmacy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Karen Korch","family":"Black","sequence":"additional","affiliation":[{"name":"Karen Korch Black PharmD, PGY2 Ambulatory Care Pharmacy Residency Program Director; Clinical Pharmacy Specialist, VA Maryland Healthcare System\u2014Department of Pharmacy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"179","published-online":{"date-parts":[[2012,11,1]]},"reference":[{"key":"bibr1-aph.1R223","doi-asserted-by":"publisher","DOI":"10.1136\/bmj.c2181"},{"key":"bibr2-aph.1R223","doi-asserted-by":"publisher","DOI":"10.1182\/asheducation-2003.1.62"},{"key":"bibr3-aph.1R223","doi-asserted-by":"publisher","DOI":"10.1001\/archinte.166.18.1975"},{"key":"bibr4-aph.1R223","doi-asserted-by":"publisher","DOI":"10.2337\/diacare.23.9.1227"},{"key":"bibr5-aph.1R223","doi-asserted-by":"publisher","DOI":"10.1136\/bmj.2.5763.685"},{"key":"bibr6-aph.1R223","volume-title":"Glucophage (metformin hydrochloride)","year":"2009"},{"key":"bibr7-aph.1R223","volume-title":"AHFS Drug Information","author":"Metformin hydrochloride","year":"2010"},{"key":"bibr8-aph.1R223","doi-asserted-by":"publisher","DOI":"10.1001\/archinte.162.4.484"},{"key":"bibr9-aph.1R223","doi-asserted-by":"publisher","DOI":"10.1097\/SMJ.0b013e3181ce0e4d"},{"key":"bibr10-aph.1R223","first-page":"979","volume":"67","author":"Oh RC","year":"2003","journal-title":"Am Fam Physician"},{"key":"bibr11-aph.1R223","first-page":"1425","volume":"83","author":"Langan RC","year":"2011","journal-title":"Am Fam Physician"},{"key":"bibr12-aph.1R223","doi-asserted-by":"publisher","DOI":"10.1111\/j.1532-5415.1995.tb07408.x"},{"key":"bibr13-aph.1R223","doi-asserted-by":"publisher","DOI":"10.1111\/j.1753-4887.2009.00163.x"},{"key":"bibr14-aph.1R223","doi-asserted-by":"publisher","DOI":"10.1159\/000093746"},{"key":"bibr15-aph.1R223","doi-asserted-by":"publisher","DOI":"10.7326\/0003-4819-124-5-199603010-00002"},{"key":"bibr16-aph.1R223","unstructured":"Urbaniak GC, Plous S. 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