Acid-base and electrolytes: diabetic ketoacidosis: 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 · Acid-base and electrolytes: diabetic ketoacidosis

Sample item

A 20-year-old with type 1 diabetes has ketoacidosis. Serum potassium on admission is 4.8 mmol/L. Despite this, potassium replacement is planned once insulin is started. What explains this?

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

The answer and the reasoning

B. Total body potassium is depleted, and insulin will drive potassium into cells

Insulin lack, hyperosmolality and acidosis shift potassium out of cells, masking the large total body deficit created by osmotic diuresis and vomiting. Insulin therapy and correction of acidosis move potassium back into cells, and serum levels can fall rapidly. Potassium is replaced when it falls below about 5.2 mmol/L, and insulin is delayed if below 3.3.

Option by option

  • A. Insulin causes renal potassium retention

    Insulin does not cause renal potassium retention; it promotes cellular uptake.

  • B. Total body potassium is depleted, and insulin will drive potassium into cells (correct)

    Correct. A masked total deficit is revealed once insulin shifts potassium into cells.

  • C. Normal potassium means no deficit exists

    A normal serum level does not exclude a large intracellular and total deficit.

  • D. Acidosis lowers extracellular potassium

    Acidosis raises extracellular potassium by exchange with hydrogen ions.

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 B, Total body potassium is depleted, and insulin will drive potassium into cells. Insulin lack, hyperosmolality and acidosis shift potassium out of cells, masking the large total body deficit created by osmotic diuresis and vomiting.

Why is "Insulin causes renal potassium retention" not the answer?

Insulin does not cause renal potassium retention; it promotes cellular uptake.

Why is "Normal potassium means no deficit exists" not the answer?

A normal serum level does not exclude a large intracellular and total deficit.

Why is "Acidosis lowers extracellular potassium" not the answer?

Acidosis raises extracellular potassium by exchange with hydrogen ions.

What concept does this question test?

It tests Acid-base and electrolytes: diabetic ketoacidosis in Biochemistry. Insulin therapy and correction of acidosis move potassium back into cells, and serum levels can fall rapidly. Potassium is replaced when it falls below about 5.2 mmol/L, and insulin is delayed if below 3.3.

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 Acid-base and electrolytes: diabetic ketoacidosis?

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.