Oral vs. Intramuscular Vitamin B12 in Vitamin B12 Deficiency The Blood Project Vitamin B12 is essential for energy production, nervous system function, and red blood cell formation. However, oral B12 supplementation doesn't work well for everyoneabsorption can be limited by digestive issues, certain medications, Vitamin B12 injections deliver high doses of this essential vitamin directly into your bloodstream for better absorption than oral supplements to boost energy, support red blood cell production and maintain nerve function. What is an acceptable oral vitamin B12 (cobalamin) supplement alternative to intramuscular injections for a patient with severely low vitamin B12 levels, particularly those with malabsorption or pernicious anemia?