Megaloblastic anemia (Vitamin B12 and folic acid) MCQs With Answer
Megaloblastic anemia, commonly due to Vitamin B12 or folic acid deficiency, is a critical topic for B.Pharm students focused on hematology and pharmacotherapy. This introduction reviews pathophysiology, diagnostic markers (MCV, hypersegmented neutrophils, methylmalonic acid, homocysteine), common etiologies (pernicious anemia, malabsorption, dietary deficiency, drug interactions), and therapeutic options (cyanocobalamin, hydroxocobalamin, oral vs IM dosing, folic acid supplementation). Understanding drug-induced causes (methotrexate, anticonvulsants, metformin, PPIs), monitoring parameters, and risks in pregnancy is essential for safe medication management and counseling. Now let’s test your knowledge with 50 MCQs on this topic.
Q1. Which biochemical marker is elevated specifically in Vitamin B12 deficiency but not in isolated folic acid deficiency?
- Serum homocysteine
- Methylmalonic acid
- Mean corpuscular volume (MCV)
- Serum folate
Correct Answer: Methylmalonic acid
Q2. The primary physiological role of Vitamin B12 (cobalamin) in hematopoiesis is as a cofactor for which enzyme?
- Thymidylate synthase
- Methionine synthase
- Glutathione peroxidase
- Ribonucleotide reductase
Correct Answer: Methionine synthase
Q3. Which of the following is a classic hematologic finding on peripheral smear in megaloblastic anemia?
- Microcytosis with target cells
- Hypersegmented neutrophils
- Acanthocytes
- Spherocytes
Correct Answer: Hypersegmented neutrophils
Q4. Pernicious anemia causes Vitamin B12 deficiency primarily due to loss of which stomach component?
- Pepsin
- Intrinsic factor
- Gastrin
- Hydrochloric acid
Correct Answer: Intrinsic factor
Q5. Which drug is commonly associated with interfering with Vitamin B12 absorption and may predispose to deficiency on long-term use?
- Metformin
- Amlodipine
- Simvastatin
- Prednisone
Correct Answer: Metformin
Q6. A pregnant woman should receive adequate folic acid to prevent which fetal complication?
- Cardiac septal defects
- Neural tube defects
- Pulmonary hypoplasia
- Cleft palate
Correct Answer: Neural tube defects
Q7. Which laboratory pattern best differentiates folate deficiency from Vitamin B12 deficiency?
- Both have elevated methylmalonic acid
- Folate deficiency has elevated methylmalonic acid only
- Vitamin B12 deficiency has elevated methylmalonic acid; both have elevated homocysteine
- Only folate deficiency elevates homocysteine
Correct Answer: Vitamin B12 deficiency has elevated methylmalonic acid; both have elevated homocysteine
Q8. Which of the following drug classes is a direct antifolate and can induce megaloblastic anemia?
- Beta-blockers
- Sulfonylureas
- Methotrexate
- Proton pump inhibitors
Correct Answer: Methotrexate
Q9. Which clinical feature is more suggestive of Vitamin B12 deficiency than isolated folate deficiency?
- Glossitis
- Gastrointestinal upset
- Neurological symptoms like paresthesia and gait ataxia
- Fatigue
Correct Answer: Neurological symptoms like paresthesia and gait ataxia
Q10. Oral high-dose cyanocobalamin therapy relies on which absorption mechanism when intrinsic factor is absent?
- Active transport by intrinsic factor
- Passive diffusion across the intestinal mucosa
- Carrier-mediated ileal uptake dependent on cubilin
- Gastric acid-dependent uptake
Correct Answer: Passive diffusion across the intestinal mucosa
Q11. Which of the following is an expected bone marrow finding in megaloblastic anemia?
- Hypocellularity with erythroid aplasia
- Hypercellular marrow with megaloblastic erythropoiesis
- Fibrotic marrow with dry tap
- Normocellular marrow with ring sideroblasts
Correct Answer: Hypercellular marrow with megaloblastic erythropoiesis
Q12. Which test was historically used to assess Vitamin B12 absorption but is rarely performed now?
- Serum methylmalonic acid
- Schilling test
- Anti-intrinsic factor antibody assay
- Serum homocysteine
Correct Answer: Schilling test
Q13. Which pathology results from prolonged untreated Vitamin B12 deficiency affecting the spinal cord?
- Posterior column demyelination and lateral corticospinal degeneration (subacute combined degeneration)
- Peripheral neuropathy limited to motor fibers
- Small fiber neuropathy without myelopathy
- Poliomyelitis-like anterior horn cell loss
Correct Answer: Posterior column demyelination and lateral corticospinal degeneration (subacute combined degeneration)
Q14. In megaloblastic anemia, which red cell index is characteristically increased?
- MCV (mean corpuscular volume)
- MCHC (mean corpuscular hemoglobin concentration)
- RDW (red cell distribution width) decreased
- Platelet mean volume decreased
Correct Answer: MCV (mean corpuscular volume)
Q15. Which dietary group is at highest risk for developing Vitamin B12 deficiency if no supplementation is taken?
- Lactose-intolerant individuals
- Strict vegans
- High-protein dieters
- Gluten-free dieters
Correct Answer: Strict vegans
Q16. Which of the following medications can exacerbate folate deficiency by inhibiting dihydrofolate reductase?
- Chloramphenicol
- Trimethoprim-sulfamethoxazole
- Metformin
- Omeprazole
Correct Answer: Trimethoprim-sulfamethoxazole
Q17. Rapid hematologic improvement after Vitamin B12 therapy is usually first evident by which parameter?
- Normalization of MCV within 24 hours
- Reticulocyte count increase within 1 week
- Normalization of methylmalonic acid in 48 hours
- Immediate resolution of neuropathy
Correct Answer: Reticulocyte count increase within 1 week
Q18. Which route of Vitamin B12 administration is preferred in severe deficiency with neurological involvement?
- Topical nasal spray only
- Oral low-dose supplementation
- Intramuscular or deep subcutaneous injections
- Intravenous infusion continuous
Correct Answer: Intramuscular or deep subcutaneous injections
Q19. Excessive ingestion of which compound can mask Vitamin B12 deficiency by correcting anemia but not neurologic damage?
- Vitamin C
- Folic acid (folate)
- Iron supplements
- Vitamin D
Correct Answer: Folic acid (folate)
Q20. Which of the following is a common laboratory pattern in megaloblastic anemia due to ineffective erythropoiesis?
- Low LDH and low indirect bilirubin
- Elevated LDH and elevated indirect bilirubin
- Low ferritin and low transferrin saturation
- Isolated thrombocytosis
Correct Answer: Elevated LDH and elevated indirect bilirubin
Q21. Which antibody test supports a diagnosis of pernicious anemia?
- Anti-parietal cell and anti-intrinsic factor antibodies
- Anti-nuclear antibodies
- Anti-dsDNA antibodies
- Anti-phospholipid antibodies
Correct Answer: Anti-parietal cell and anti-intrinsic factor antibodies
Q22. Which medication used long-term can reduce gastric acidity and thereby impair Vitamin B12 absorption?
- Proton pump inhibitors (PPIs)
- Statins
- ACE inhibitors
- Beta-lactam antibiotics
Correct Answer: Proton pump inhibitors (PPIs)
Q23. Folic acid is essential for synthesis of which DNA precursor nucleotide?
- ATP
- Deoxythymidine monophosphate (dTMP)
- Guanosine triphosphate (GTP)
- Cytidine triphosphate (CTP)
Correct Answer: Deoxythymidine monophosphate (dTMP)
Q24. Which statement regarding oral versus intramuscular Vitamin B12 therapy is true for many patients with deficiency?
- Oral Vitamin B12 is never effective without intrinsic factor
- High-dose oral B12 can be effective through passive absorption even without intrinsic factor
- Intramuscular B12 is only indicated for mild deficiency
- Oral B12 causes more adverse effects than IM injections
Correct Answer: High-dose oral B12 can be effective through passive absorption even without intrinsic factor
Q25. Which of the following conditions can lead to combined deficiency of folate due to increased requirements?
- Chronic alcoholism and pregnancy
- Hypothyroidism
- Osteoarthritis
- Parkinson disease
Correct Answer: Chronic alcoholism and pregnancy
Q26. Which lab parameter is typically low in megaloblastic anemia due to ineffective erythropoiesis?
- Mean corpuscular volume (MCV)
- Reticulocyte count
- Serum ferritin
- White blood cell count always increased
Correct Answer: Reticulocyte count
Q27. Which enzyme deficiency or dysfunction leads to increased methylmalonic acid when Vitamin B12 is lacking?
- Methionine synthase dysfunction
- Methylmalonyl-CoA mutase dysfunction
- Thymidylate synthase dysfunction
- Dihydrofolate reductase dysfunction
Correct Answer: Methylmalonyl-CoA mutase dysfunction
Q28. Which of the following antibiotics can exacerbate or cause megaloblastic anemia by bone marrow suppression?
- Amoxicillin
- Chloramphenicol
- Azithromycin
- Ciprofloxacin
Correct Answer: Chloramphenicol
Q29. Which monitoring parameter is most appropriate after initiating folic acid therapy in folate-deficient anemia?
- Weekly serum Vitamin B12 levels
- Reticulocyte response within 1–2 weeks and hemoglobin rise over 2–4 weeks
- Daily MCV monitoring
- Monthly anti-intrinsic factor antibody testing
Correct Answer: Reticulocyte response within 1–2 weeks and hemoglobin rise over 2–4 weeks
Q30. Which clinical scenario should prompt measurement of both serum B12 and methylmalonic acid concentrations?
- Microcytic anemia with low ferritin
- Macrocytic anemia with borderline serum B12 level
- Isolated thrombocytosis
- Elevated hemoglobin with polycythemia
Correct Answer: Macrocytic anemia with borderline serum B12 level
Q31. Which of the following is a pharmacological form of Vitamin B12 commonly used for parenteral therapy?
- Cyanocobalamin
- Folinic acid
- Folic acid
- Hydrochlorothiazide
Correct Answer: Cyanocobalamin
Q32. Which of the following is true about folinic acid (leucovorin) compared to folic acid?
- Folinic acid requires dihydrofolate reductase activation to be active
- Folinic acid bypasses dihydrofolate reductase and is used to rescue methotrexate toxicity
- Folinic acid is identical to Vitamin B12 in function
- Folinic acid causes irreversible neuronal damage
Correct Answer: Folinic acid bypasses dihydrofolate reductase and is used to rescue methotrexate toxicity
Q33. Which is the most appropriate approach when a patient has megaloblastic anemia and low B12 with positive anti-intrinsic factor antibodies?
- High-dose oral folic acid only
- Start intramuscular Vitamin B12 replacement and evaluate for autoimmune gastritis
- Observe without therapy
- Start iron supplementation only
Correct Answer: Start intramuscular Vitamin B12 replacement and evaluate for autoimmune gastritis
Q34. Which metabolic consequence occurs when Vitamin B12 deficiency impairs methionine synthase activity?
- Decreased homocysteine and increased methionine
- Accumulation of homocysteine and impaired methylation reactions
- Increased dTMP synthesis
- Enhanced folate activation
Correct Answer: Accumulation of homocysteine and impaired methylation reactions
Q35. Which is a common initial pharmacotherapeutic regimen for severe symptomatic B12 deficiency with neurological signs?
- Oral folic acid 0.4 mg daily
- IM cyanocobalamin 1000 µg daily for 1 week then weekly for 4 weeks, then monthly
- Intravenous iron infusion
- Methotrexate weekly
Correct Answer: IM cyanocobalamin 1000 µg daily for 1 week then weekly for 4 weeks, then monthly
Q36. Which condition can produce a functional folate deficiency by trapping folate as 5-methyl-THF when B12 is absent?
- Vitamin B12 deficiency (methyl trap hypothesis)
- Iron overload
- Hypercalcemia
- Hypothyroidism
Correct Answer: Vitamin B12 deficiency (methyl trap hypothesis)
Q37. Which pharmacologic agent used in rheumatoid arthritis can lead to folate deficiency and is often co-prescribed with folinic acid?
- Sulfasalazine
- Hydroxychloroquine
- Methotrexate
- Etanercept
Correct Answer: Methotrexate
Q38. Which feature in a patient with macrocytic anemia suggests bone marrow failure is less likely and megaloblastic process is more likely?
- Hypocellular marrow on biopsy
- Hypersegmented neutrophils on peripheral smear
- Marked reticulocytosis at presentation
- Low MCV
Correct Answer: Hypersegmented neutrophils on peripheral smear
Q39. Which laboratory abnormality is expected in both folate and B12 deficiencies?
- Low homocysteine
- Elevated serum homocysteine
- Normal MCV
- Low methylmalonic acid
Correct Answer: Elevated serum homocysteine
Q40. Which patient population requires higher folic acid supplementation recommendations to prevent deficiency?
- Older adults with low caloric intake
- Women of childbearing potential and pregnant women
- Patients on chronic proton pump inhibitors
- People with vitamin D deficiency
Correct Answer: Women of childbearing potential and pregnant women
Q41. Which of the following is TRUE about nitrous oxide exposure in relation to B12?
- Nitrous oxide enhances Vitamin B12 activity
- Nitrous oxide oxidizes cobalamin, inactivating methylcobalamin and precipitating deficiency
- Nitrous oxide only affects folate metabolism
- Nitrous oxide is protective against megaloblastic anemia
Correct Answer: Nitrous oxide oxidizes cobalamin, inactivating methylcobalamin and precipitating deficiency
Q42. Which of the following is an important pharmacy counseling point for patients starting B12 injections?
- They can stop therapy once hemoglobin normalizes even if cause is pernicious anemia
- Adherence to long-term replacement may be necessary, and monitoring of neurological symptoms is important
- Oral antibiotics should be used concurrently
- B12 injections cure autoimmune gastritis
Correct Answer: Adherence to long-term replacement may be necessary, and monitoring of neurological symptoms is important
Q43. Which of the following is a potential hematologic adverse effect of prolonged methotrexate therapy without folinic rescue?
- Macrocytic megaloblastic anemia
- Hemolytic anemia due to G6PD deficiency
- Iron deficiency anemia only
- Polycythemia vera
Correct Answer: Macrocytic megaloblastic anemia
Q44. In patients with suspected megaloblastic anemia, which initial blood test is most helpful to quantify red blood cell size?
- Platelet count
- Mean corpuscular volume (MCV)
- Serum creatinine
- Blood glucose
Correct Answer: Mean corpuscular volume (MCV)
Q45. Which sign on neurologic examination is characteristic of posterior column involvement in B12 deficiency?
- Loss of vibration and position sense
- Peripheral hyperreflexia only
- Upper motor neuron flaccid paralysis
- Cranial nerve palsies
Correct Answer: Loss of vibration and position sense
Q46. Which laboratory result would you expect in a patient with severe folate deficiency?
- Low MCV and microcytosis
- Macrocytosis with low serum folate and elevated homocysteine
- Low methylmalonic acid and normal homocysteine
- Isolated thrombocytosis with normal RBC indices
Correct Answer: Macrocytosis with low serum folate and elevated homocysteine
Q47. Which over-the-counter supplement is commonly recommended for women planning pregnancy to reduce neural tube defects?
- Vitamin B12 only
- Folic acid 400–800 µg daily
- High-dose iron 100 mg daily only
- Vitamin E 1000 IU daily
Correct Answer: Folic acid 400–800 µg daily
Q48. Which of the following is an example of a drug interaction that can lead to decreased folate levels?
- Concurrent use of methotrexate and folinic acid (rescue)
- Use of trimethoprim inhibiting bacterial dihydrofolate reductase and contributing to folate deficiency
- Use of proton pump inhibitors increasing folate absorption
- Use of vitamin C degrading folate
Correct Answer: Use of trimethoprim inhibiting bacterial dihydrofolate reductase and contributing to folate deficiency
Q49. In a patient with macrocytic anemia and neurological symptoms, what is the risk of treating empirically with folic acid alone without addressing possible B12 deficiency?
- No risk; folic acid will reverse both anemia and neurologic damage
- Folic acid may correct hematologic abnormalities but can allow progression or worsening of neurologic damage due to uncorrected B12 deficiency
- Folic acid is toxic and will precipitate hemolysis
- Folic acid converts to B12 in vivo
Correct Answer: Folic acid may correct hematologic abnormalities but can allow progression or worsening of neurologic damage due to uncorrected B12 deficiency
Q50. Which counseling point is important for patients on long-term metformin with regard to B12?
- Metformin increases B12 absorption; no monitoring needed
- Long-term metformin use can reduce B12 levels; periodic monitoring and supplementation if low are recommended
- Metformin causes folate overdose
- Metformin directly causes hemolysis unrelated to B12
Correct Answer: Long-term metformin use can reduce B12 levels; periodic monitoring and supplementation if low are recommended
