This case has been edited so that the patient is de-identified.  The patient was a prepubertal girl with a learning and social disability for which she was receiving non-traditional treatments. Her vitamin B12 level was found to be greater than 50,000 pg/mL with an upper limit of the reference interval being 1200 pg/mL. How could her vitamin B12 level be so high and what effects could this have on the child? The answer will be presented in 1 week.

Answer: For unclear reasons, the child was receiving more than 20 mg of vitamin B12 injected at least 3 times per week (note: there is no medicinally accepted reason to treat learning and social disability with vitamin B12). While vitamin B12 is not generally toxic even at very high concentrations, high B12 levels can be seen in a number of pathologic conditions. The list below provides the upper limits of vitamin B12 levels reported in a number of pathologic conditions (1):

Highest vitamin B12 concentrations:

 Hypereosinophilia syndrome  10,000 - 25,000 pmol/L*
 Metastatic liver disease  10,000 - 25,000 pmol/L*
 Acute hepatitis  5,000 - 10,000 pmol/L
 Cirrhosis  5,000 - 10,000 pmol/L
 Hepatocellular carcinoma  5,000 - 10,000 pmol/L
 Chronic myelogenous leukemia  5,000 - 10,000 pmol/L
 Cystic fibrosis  2,500 - 5,000 pmol/L
 Polycythemia vera  1,000 - 2,500 pmol/L

* To convert SI units (pmol/L) to English units (pg/mL) divide pmol/L by 0.738.


  1. Ermensa AAM, Vlasveldb LT, Lindemansc J. Significance of elevated cobalamin (vitamin B12) levels in blood. Clinical Biochemistry 36 (2003) 585–590