NCLEX-RN Study Guide

NCLEX Endocrine Questions: Diabetes and Thyroid (2026)

November 2, 2026 · 5 min read

Short answer. Endocrine NCLEX questions turn on recognising which hormone is missing or excessive, and then acting on the consequence. Hypoglycemia is the emergency you must treat first, because it damages the brain in minutes.

What the 2026 NCLEX tests in this area

Physiological Adaptation: diabetes, DKA, thyroid storm, adrenal crisis
Pharmacological and Parenteral Therapies: insulin types, levothyroxine, corticosteroids

Key facts to know

Hypoglycemia threshold	Below 70 mg/dL, treat immediately with 15 g of fast acting carbohydrate
Normal fasting glucose	70 to 99 mg/dL
Diabetes diagnostic A1C	6.5 percent or higher
DKA hallmarks	Glucose above 250, ketones, metabolic acidosis, Kussmaul respirations
Levothyroxine teaching	Take on an empty stomach, 30 to 60 minutes before breakfast, and report palpitations
Steroid teaching	Never stop abruptly. Taper, and expect rising glucose and increased infection risk

Practice question from this chapter

A client with diabetic ketoacidosis had blood glucose 520 mg/dL, potassium 5.9 mEq/L, and bicarbonate 10 mEq/L. An insulin infusion was started. Two hours later the glucose is 300 mg/dL and the potassium is 4.2 mEq/L. Which action should the nurse anticipate next?

Continue the insulin infusion without any changes
Stop the insulin infusion because the glucose is falling
Administer a potassium-binding agent
Add potassium to the intravenous fluids per protocol

Show answer and rationale

Correct answer: D. Add potassium to the intravenous fluids per protocol

The correct action is to add potassium to the intravenous fluids per protocol because insulin drives potassium back into the cells, and as the potassium falls into the normal range, replacement is needed to prevent hypokalemia. Continuing without changes risks dangerous hypokalemia. Stopping the insulin is incorrect because the glucose is still elevated, and a binding agent is for hyperkalemia, not the current level.

Second practice question

A client with diabetic ketoacidosis is on an insulin infusion. The glucose has fallen from 620 mg/dL to 250 mg/dL, and the potassium is now 3.2 mEq/L. Which action should the nurse implement?

Add potassium to the intravenous fluids
Increase the insulin infusion rate
Hold the insulin infusion
Administer sodium bicarbonate

Show answer and rationale

Correct answer: A. Add potassium to the intravenous fluids

As insulin drives glucose into cells, potassium moves intracellularly and the serum level falls; potassium must be replaced to prevent life-threatening dysrhythmias. Increasing insulin worsens the hypokalemia. Holding insulin stops ketoacidosis treatment. Bicarbonate is reserved for severe acidosis and does not address the potassium.

Treat hypoglycemia first, always

If a diabetic client is confused, sweaty and shaky, treat before you confirm. A conscious client gets 15 g of fast acting carbohydrate and a recheck in 15 minutes. An unconscious client gets glucagon or intravenous dextrose. Waiting for a glucometer reading when the client cannot protect their airway is the wrong answer every time.

DKA looks different: deep rapid breathing, fruity breath, abdominal pain and dehydration. The treatment is fluid first, then insulin, then potassium replacement, because insulin drives potassium into cells and can cause a dangerous drop.

Thyroid and adrenal opposites

Hyperthyroidism is fast: weight loss, heat intolerance, tachycardia, anxiety. Hypothyroidism is slow: weight gain, cold intolerance, bradycardia, fatigue. For Addison disease expect low cortisol, low sodium and high potassium. For Cushing syndrome expect the reverse. Learn them as pairs and most items resolve in one step.

Which hormone is missing, which is excessive

Almost every endocrine item resolves into one of those two questions. Low cortisol means Addison disease with low sodium, high potassium and hypotension. Excess cortisol means Cushing syndrome with high sodium, low potassium, high glucose and a wound that will not heal. Low thyroid hormone means slow and cold, excess means fast and hot.

For diabetes the question becomes which direction the glucose is moving and how fast. Hypoglycaemia needs carbohydrate within minutes. Hyperglycaemia with ketones and acidosis needs fluid first, then insulin, then potassium.

Steroid and thyroid teaching items

Two teaching points win items repeatedly. Corticosteroids are never stopped abruptly, because the adrenal glands have stopped producing their own cortisol. Levothyroxine is taken on an empty stomach at the same time daily, and the client reports palpitations, weight loss or insomnia because those suggest the dose is now too high.

Expect the exam to ask what the client should report rather than what the nurse should do. The answer is nearly always the symptom of too much or too little of the hormone you have just replaced.

Frequently asked questions

What do I do first for a hypoglycemic client who is unconscious?

Give glucagon or intravenous dextrose. Do not attempt oral carbohydrates when the airway is not protected.

Why does potassium matter in DKA?

Insulin moves potassium into cells, so total body potassium is low even when the serum value looks normal. Replacement is part of treatment.

Can a steroid be stopped abruptly?

No. Abrupt withdrawal can cause adrenal crisis. Corticosteroids must be tapered.

What is the difference between Addison and Cushing?

Addison is cortisol deficiency with low sodium and high potassium. Cushing is cortisol excess with high sodium, low potassium and high glucose.

How do I tell DKA from hyperosmolar hyperglycaemic state?

DKA has ketones and acidosis with a moderately high glucose and a client who is usually younger and vomiting. Hyperosmolar state has a very high glucose, profound dehydration and altered consciousness with minimal ketones.

When is insulin given in DKA?

After fluids are started and potassium is confirmed above the replacement threshold, because insulin drives potassium into cells and can cause a dangerous drop.

Practise this chapter with rationales

NCLEXDeck gives you practice questions for every body system, with a rationale for the correct answer and for each distractor. Start on the free tier, no card required.

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