The route used for the first dose of vitamin B-12 in pernicious anemia is which?

• A. Oral
• B. Intramuscular
• C. Subcutaneous
• D. Intravenous

Answer: (B)

Pernicious anemia involves a lack of intrinsic factor, so the body cannot reliably absorb vitamin B-12 through the gut. To replenish stores quickly and reliably, the first dose is given by intramuscular injection, bypassing the digestive tract entirely. This route delivers B-12 directly into the bloodstream, ensuring rapid repletion and helping prevent neurologic complications that can arise from deficiency. After stabilization, ongoing therapy is usually monthly intramuscular injections. While high-dose oral B-12 can work in some situations, it is not dependable in pernicious anemia because absorption still depends on intrinsic factor. Intravenous administration is not the standard for initial repletion, as intramuscular injections provide a practical depot and are easier to administer long-term.