Elevated B12: A Cross-Sectional Survey of Disease Associations and Attitudes of General Practitioners and Medical Students

Introduction Elevated serum B12 (hypercobalaminaemia) has been linked to malignancies, liver disease, and increased mortality. Two additional concepts complicate interpretation. B12 pseudo-hypervitaminosis is a paradoxical state of elevated B12 in serum but intracellularly unavailable, leading to functional deficiency and B12-deficiency symptoms. Pseudo-hypercobalaminaemia is a laboratory artefact, with elevated B12 detected despite true low levels. Despite significant clinical implications, raised B12 is overlooked in primary care and medical education. This pilot study aims to assess the awareness of general practitioners (GPs) and medical students regarding the clinical implications of elevated serum B12. Methods A cross-sectional survey of 46 UK-based GPs and 50 medical students was conducted electronically using convenience sampling. The survey assessed candidates' awareness of causes, consequences, investigations, and management of high serum B12. Results Among 46 GPs, 41 (89.2%) recognised at least one disease association with hypercobalaminaemia compared to 11 (22%) of 50 medical students (p < 0.0001). Common associations included malignancy, haematological conditions, and liver pathology. Neither group demonstrated awareness of pseudo-hypercobalaminaemia or B12 pseudo-hypervitaminosis. A total of 30 (65%) GPs and 27 (54%) medical students would investigate elevated B12, yet these approaches were highly variable and frequently inappropriate. Awareness of disease associations significantly increased the likelihood of choosing an appropriate investigation (p < 0.0001). Most respondents reported receiving no formal teaching on elevated B12 levels. GPs and medical students were similar in their support for changing cancer guidelines to reflect hypercobalaminaemia, yet awareness of disease links did not significantly impact support. The qualification date of GPs did not significantly impact their awareness, investigative approaches, or attitude towards guideline changes. Conclusions This pilot survey demonstrates a clear gap in clinician understanding of hypercobalaminaemia and the lack of standardised investigative approaches. Larger, multi-centred studies are needed to develop and validate practical diagnostic pathways for primary care.