Diabetes: metformin and renal impairment: practice question

A General Medicine 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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General Medicine · Diabetes: metformin and renal impairment

Sample item

A 70-year-old man with type 2 diabetes takes metformin 1 g twice daily. After an episode of acute kidney injury his eGFR is 24 mL/min/1.73 m2. What is the main reason to stop the drug?

ARisk of severe hypoglycaemia from increased insulin releaseBRisk of lactic acidosis from drug accumulationCRisk of weight gain with fluid retentionDRisk of euglycaemic ketoacidosis

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

The answer and the reasoning

B. Risk of lactic acidosis from drug accumulation

Metformin is eliminated unchanged by the kidney and reduces hepatic gluconeogenesis and lactate clearance. With an eGFR below 30 it accumulates, and the risk of metformin-associated lactic acidosis rises, so it is contraindicated. Insulin or a DPP-4 inhibitor such as linagliptin, which needs no renal dose adjustment, can be used instead.

Option by option

A. Risk of severe hypoglycaemia from increased insulin release
Metformin does not stimulate insulin secretion, so it rarely causes hypoglycaemia when used alone; sulfonylureas do.
B. Risk of lactic acidosis from drug accumulation (correct)
Accumulation of metformin raises lactate and causes metabolic acidosis when eGFR is below 30.
C. Risk of weight gain with fluid retention
Weight gain and oedema are features of thiazolidinediones, whereas metformin is weight neutral or reduces weight.
D. Risk of euglycaemic ketoacidosis
Euglycaemic ketoacidosis is an adverse effect of SGLT2 inhibitors.

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.

Questions about this General Medicine question

What is the answer to this General Medicine question?

The best answer is B, Risk of lactic acidosis from drug accumulation. Metformin is eliminated unchanged by the kidney and reduces hepatic gluconeogenesis and lactate clearance.

Why is "Risk of severe hypoglycaemia from increased insulin release" not the answer?

Metformin does not stimulate insulin secretion, so it rarely causes hypoglycaemia when used alone; sulfonylureas do.

Why is "Risk of weight gain with fluid retention" not the answer?

Weight gain and oedema are features of thiazolidinediones, whereas metformin is weight neutral or reduces weight.

Why is "Risk of euglycaemic ketoacidosis" not the answer?

Euglycaemic ketoacidosis is an adverse effect of SGLT2 inhibitors.

What concept does this question test?

It tests Diabetes: metformin and renal impairment in General Medicine. With an eGFR below 30 it accumulates, and the risk of metformin-associated lactic acidosis rises, so it is contraindicated. Insulin or a DPP-4 inhibitor such as linagliptin, which needs no renal dose adjustment, can be used instead.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. 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 Diabetes: metformin and renal impairment?

For each disease know the classic presentation, the best test, and the first-line treatment. Then use the flashcards and the other General Medicine 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.