Why did her NP prescribe vitamin B12 by intramuscular injection rather than orally?

Deb Smith, age 56, came to her nurse practitioner (NP) with fatigue, pallor, dyspnea on exertion, and palpitations. Her laboratory report indicates that her hematocrit, hemoglobin, and reticulocyte counts are low; that her MCV is high; and that her MCH and MCHC are normal. Her diagnosis is pernicious anemia.
Answer the following questions regarding Deb’s anemia and provide the pathophysiology associated with the body’s response to this disease process.
• Why should Deb’s NP ask her about paresthesia and ataxia?
• Why did her NP prescribe vitamin B12 by intramuscular injection rather than orally?
• What causes pernicious anemia?
• What are the technical terms that describe an anemia with high MCV and normal MCH?