B12 deficiency epidemic? Should B12 level lower limit reference values be decreased?

Abstract

Background: This study aims to examine B12 levels in general in our society, to determine the rates of B12 deficiency, and to determine and recommend new B12 reference range values according to current data. Methods: A total of 16497 patients who were admitted to our secondary care hospital for various reasons in the three-year period between January 2021 and December 2023 and whose B12 levels were tested in their serum were included in the study. B12 levels of all patients were measured in the hospital biochemistry laboratory on Architect i1000SR and i2000 SR (Abbott diagnostics, Ireland) devices. Results: The reference ranges for B12 levels, determined as 2.5% and 97.5%, were 130-1084 pg/ml for adult men, and as 137-993 pg/ml for adult women. Considering 200 pg/ml as the normal lower limit for B12 level, low levels were found in 14.6% of all patients. Conclusions: Our study is one of the rare studies in which B12 reference ranges are investigated up-to-date with a large patient participation. Our findings showed that the rate of B12 deficiency in the society is very high compared to the generally accepted reference lower limit values, that B12 levels in the society are very low compared to these reference values, and perhaps that the reference lower limit values may need to be reduced to 149-138 pg/ml in individuals under 18 years of age, 130-137 pg/ml in adults, and 123-125 pg/ml in the elderly.