Nicotinamide N-methyltransferase
Conditions associated with elevated B12 levels include: Liver disease : Hepatocellular damage releases stored B12 into circulation, with levels correlating with disease severity in conditions such as cirrhosis, hepatitis, and hepatocellular carcinoma Renal impairment : Reduced kidney function decreases B12 clearance, leading to accumulation Haematological malignancies : Myeloproliferative disorders, acute leukaemia, and polycythaemia vera can elevate B12 through increased production of B12-binding proteins (transcobalamins) Solid tumours : Certain cancers, particularly those affecting the liver or gastrointestinal tract, may elevate B12 levels A specific concern relates to cyanocobalamin in patients with Leber's hereditary optic neuropathy , a rare mitochondrial disorder
On the other hand, a person with more muscle mass may require a slightly longer needle for an intramuscular shot to reach the muscle effectively
As noted, the present knowledge is limited, and these are considerations, not strong recommendations
This matters most for people whose bodies struggle to absorb B12 from food or pills
