Its not something most people need to worry about due to how rare it is, but if unusual rashes occur after starting B12, speak with your doctor, and a skin patch test to check for allergies to metals may help to identify an issue
If this is a concern of yours, be sure to bring it up during your consultation
Deficiency has also been linked with a higher likelihood of pre-eclampsia, gestational diabetes and excess weight gain during pregnancy
A physician investigating unexplained hypercobalaminemia will typically order some combination of the following: Complete blood count (CBC) with differential to check for abnormal red blood cell, white blood cell, or platelet counts Liver function tests (ALT, AST, ALP, bilirubin, albumin) to assess liver health Kidney function tests (creatinine, BUN, estimated GFR) to evaluate renal clearance Peripheral blood smear if a myeloproliferative disorder is suspected Abdominal imaging (ultrasound or CT) if liver or abdominal pathology is a concern Cancer-specific markers or screenings if clinical suspicion warrants them The NIH Office of Dietary Supplements fact sheet notes that observational data from a Danish registry analysis of 757,185 people found the adjusted 1-year cancer risk was 1.74 to 4.72 times higher among those with B12 above 813 pg/mL compared to those in the normal range of 203 to 813 pg/mL
