Giving vitamin B12 parenterally? Which electrolyte should you check first? Answer: Potassium. And why does it matter? Because rapid correction of severe B12 deficiency can trigger a surge in At Home Vitamin B12 4 Week Injection Package MUST BE A FLORIDA RESID CardioMender, MD Hydroxo Vitamin B12 Supplement Injection 1000mcg 1ml 3Pk CYANOCOBALAMIN INJECTION, USP 30000 mcg 30 mL (1000 mcg mL) 30 mL VIAL B12 vitamin Store Vitamin B12 Injection 2000mcg 10ml Vial