Both may be contraindicated if you have: Personal or family history of medullary thyroid carcinoma, Multiple Endocrine Neoplasia syndrome type 2, history of severe pancreatitis, current pregnancy or plans to become pregnant, or severe kidney disease
Lyophilized stability: Up to 36 months at -20C in a sealed vial protected from light and moisture
Testing and Prescribing Vitamin B12 in Swiss General Practice: A Survey among Physicians
Therefore, parenteral cyanocobalamin should be administered to a pregnant woman if the benefits outweigh the risks.[15][16] Cyanocobalamin is excreted in the breast milk of nursing women in levels similar to the level of vitamin B12 in maternal plasma.[25] The distributed cyanocobalamin in breast milk has been found to be compatible with breastfeeding by the American Academy of Pediatrics.[26] In addition, there has not been any reports of adverse effects associated with the intake of normal daily requirements of vitamin B12 during lactation
Thats what the Harvard study found, too: High intake of vitamin B12 alone was not associated with increased fracture risk
no completed human clinical trials