Blood and immunity: folate versus B12 deficiency: practice question

A Physiology 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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Physiology · Blood and immunity: folate versus B12 deficiency

Sample item

A chronic alcohol user has macrocytic anaemia with hypersegmented neutrophils but no neurological signs. Serum homocysteine is raised while methylmalonic acid is normal. Which deficiency is most likely?

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

The answer and the reasoning

C. Folate

Folate is needed to remethylate homocysteine, so deficiency raises homocysteine. Methylmalonic acid rises only in vitamin B12 deficiency, which also causes neurological damage. A normal methylmalonic acid therefore points away from B12.

Option by option

  • A. Vitamin B6

    Vitamin B6 deficiency causes sideroblastic anaemia and neuropathy rather than macrocytosis.

  • B. Vitamin B12

    B12 deficiency raises both homocysteine and methylmalonic acid and causes neurological signs.

  • C. Folate (correct)

    Correct. Folate deficiency raises homocysteine but leaves methylmalonic acid normal.

  • D. Iron

    Iron deficiency causes a microcytic anaemia and does not cause hypersegmented neutrophils.

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 Physiology question

What is the answer to this Physiology question?

The best answer is C, Folate. Folate is needed to remethylate homocysteine, so deficiency raises homocysteine.

Why is "Vitamin B6" not the answer?

Vitamin B6 deficiency causes sideroblastic anaemia and neuropathy rather than macrocytosis.

Why is "Vitamin B12" not the answer?

B12 deficiency raises both homocysteine and methylmalonic acid and causes neurological signs.

Why is "Iron" not the answer?

Iron deficiency causes a microcytic anaemia and does not cause hypersegmented neutrophils.

What concept does this question test?

It tests Blood and immunity: folate versus B12 deficiency in Physiology. Methylmalonic acid rises only in vitamin B12 deficiency, which also causes neurological damage. A normal methylmalonic acid therefore points away from B12.

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 Blood and immunity: folate versus B12 deficiency?

For each system, sketch the key graph (pressure–volume loop, oxygen dissociation curve, nephron handling) and explain it aloud. Then use the flashcards and the other Physiology 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.