The short answer is maybe. If you have a B12 level higher than normal, being screened for a variety of cancers is not a bad idea. The risk is higher for a range of cancers. Keep in mind this is an elevation in B12 that is not in response to taking a lot of B12 supplements. ( http://www.b12-vitamin.com/ blood-levels/ ) Here's the risk from a range of different cancers. (Image from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3848986/) The key is that the marker may not only tell if you are at higher risk, it may also tell your chances of survival. " When testing for trend in survival rates between the three Cbl level groups, we observed trends toward lower survival with higher Cbl levels for all three follow-up periods for both patients with localised and non-localised cancer. The differences in survival with higher Cbl levels were similar after 2, 5 and 10 years" ( https://www.sciencedirect.com/ science/article/pii/S187778211 5002854 ) B12,...