Vitamins: B12 after ileal resection: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Vitamins: B12 after ileal resection

Sample item

A 40-year-old man had 80 cm of terminal ileum resected for Crohn disease 3 years ago. He now has macrocytic anaemia, paraesthesiae and impaired vibration sense. Serum folate is normal and B12 is very low. What is the most appropriate treatment?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Parenteral vitamin B12 for life

The intrinsic factor-B12 complex is absorbed through cubilin receptors in the terminal ileum, so resection causes permanent malabsorption. Intrinsic factor is not the missing element, so adding it is useless. Parenteral hydroxocobalamin or cyanocobalamin is given lifelong. Folic acid alone can correct the anaemia while allowing neurological damage to progress.

Option by option

  • A. Oral iron

    Iron treats iron deficiency, and this anaemia is macrocytic with B12 deficiency.

  • B. Oral vitamin B12 with intrinsic factor

    Intrinsic factor is produced normally by the stomach, and the defect is at the ileal receptor.

  • C. Parenteral vitamin B12 for life (correct)

    Bypassing the absorption site with injections corrects both haematological and neurological deficits.

  • D. Oral folic acid alone

    Folic acid alone corrects anaemia but allows subacute combined degeneration to progress.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is C, Parenteral vitamin B12 for life. The intrinsic factor-B12 complex is absorbed through cubilin receptors in the terminal ileum, so resection causes permanent malabsorption.

Why is "Oral iron" not the answer?

Iron treats iron deficiency, and this anaemia is macrocytic with B12 deficiency.

Why is "Oral vitamin B12 with intrinsic factor" not the answer?

Intrinsic factor is produced normally by the stomach, and the defect is at the ileal receptor.

Why is "Oral folic acid alone" not the answer?

Folic acid alone corrects anaemia but allows subacute combined degeneration to progress.

What concept does this question test?

It tests Vitamins: B12 after ileal resection in Biochemistry. Intrinsic factor is not the missing element, so adding it is useless. Parenteral hydroxocobalamin or cyanocobalamin is given lifelong. Folic acid alone can correct the anaemia while allowing neurological damage to progress.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Vitamins: B12 after ileal resection?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.