Background: Severe vitamin B12 (cobalamin) deficiency is rare, but international reports show that up to 26 % of the general population may have subclinical vitamin B12 deficiency. The prevalence of vitamin B12 deficiency has not been investigated in Norway. Since 2017, treatment with vitamin B12 tablets has represented an alternative to traditional treatment with intramuscular injections in Norway. When we studied the transition from injection to tablet treatment, we discovered an unexpected difference in the counties' use of vitamin B12 supplements, which we wished to investigate in more detail.
Material and method: Data on the dispensing of vitamin B12 supplements from pharmacies in 2020, broken down by the patients' county of residence, were retrieved from the Norwegian Prescription Database. The Norwegian Health Economics Administration (Helfo) provided figures on the number of reimbursed vitamin B12-related laboratory tests in 2020, classified by patients' municipality of residence.
Results: In 2020, the sale of vitamin B12 supplements on prescription in Norway amounted to 12 defined daily doses (DDD) per inhabitant and varied from 7 to 15 between the counties. The number of laboratory analyses that were performed varied by county from 26 to 46 per 100 inhabitants for total vitamin B12, and from 21 to 37 for folate. The number of analyses varied correspondingly from 1 to 12 per 100 inhabitants for homocysteine, from 1 to 13 for methylmalonic acid and from 0.01 to 8.13 for active vitamin B12.
Interpretation: Our study showed large intercounty differences in the consumption of vitamin B12 supplements. These differences may have a number of explanations. Variations in the number of vitamin B12-related laboratory analyses requisitioned may indicate that doctors' assessment and diagnosis of vitamin B12 deficiency could be a contributory factor.