NCLEX Endocrine Review: Diabetes, DKA, and Thyroid

Quick answer: For the NCLEX, endocrine review centers on diabetes: know insulin onset, peak, and duration; treat hypoglycemia (glucose under 70 mg/dL) first, using the rule of 15 if the patient is awake and can swallow; and in DKA or HHS give isotonic fluids before insulin, holding insulin until K+ is at least 3.3 mEq/L (the exam-taught threshold; the 2024 ADA consensus report uses 3.5 mEq/L). Then know thyroid storm vs myxedema coma, Addison vs Cushing, and SIADH vs DI.

Endocrine questions on the NCLEX test whether you can spot DKA before a patient crashes, teach insulin accurately, and differentiate a thyroid storm from myxedema coma. The hormonal systems feel abstract until you anchor them in patient scenarios — then they become predictable.

Key takeaways

• Know the hormone, know the disease. Too little insulin means hyperglycemia and ketones; too much thyroid means hypermetabolism; too little cortisol means you cannot handle stress.
• In DKA and HHS, fluids come before insulin — isotonic NS first to restore volume — and potassium comes before insulin if K+ is under 3.3 mEq/L.
• DKA vs HHS in one line: DKA is acidotic with ketones (more often type 1, glucose ~250–600); HHS has minimal/no ketones and minimal acidosis (more often type 2 and older adults, glucose often over 600).
• Hypoglycemia (glucose under 70) is the faster killer — treat it first with the rule of 15 if the patient is awake, or D50W/glucagon if not.
• Insulin timing predicts hypoglycemia risk. Know onset/peak/duration; long-acting basal insulins (glargine, detemir, degludec) have no pronounced peak and are never mixed with other insulins.
• For teaching questions, pick the answer that prevents a crisis — sick-day rules, site rotation, and never stopping basal insulin or steroids abruptly.

How the NCLEX frames endocrine questions

Expect diabetes to dominate: type 1 vs type 2 differences, insulin timing, DKA, HHS, hypoglycemia rescue, and patient teaching. Thyroid, adrenal, and pituitary disorders show up with classic presentations — Graves vs Hashimoto, Cushing vs Addison, SIADH vs DI. Matrix and bowtie items often ask you to sort assessment findings to the correct disorder or to choose the actions to take and the parameters to monitor; drag-and-drop items may ask you to sequence priority actions.

Three anchors will carry you:

• Know what the hormone does, and you know the disease. Too little insulin means hyperglycemia and ketones. Too much thyroid means hypermetabolism. Too little cortisol means you cannot handle stress.
• Fluids before insulin in DKA. The patient is profoundly volume-depleted; insulin without fluids drops the glucose too fast and strands the patient hypotensive and hypokalemic.
• Hypoglycemia is the faster killer. A glucose of 40 takes a life before a glucose of 400. Treat hypoglycemia first, every time.

Diabetes mellitus: type 1 vs type 2

• Type 1: Autoimmune destruction of beta cells. Absolute insulin deficiency. Typically diagnosed in childhood or adolescence. Patients require insulin for life. Prone to DKA.
• Type 2: Insulin resistance plus relative insulin deficiency. Typically adult onset, strongly linked to obesity and metabolic syndrome. Managed with lifestyle, oral agents (metformin first line), GLP-1 agonists, SGLT2 inhibitors, and insulin when needed. Prone to HHS more than DKA.

Diagnostic criteria (ADA)

• Fasting glucose ≥ 126 mg/dL on two occasions
• 2-hour oral glucose tolerance test ≥ 200 mg/dL
• Random glucose ≥ 200 mg/dL with classic symptoms
• A1C ≥ 6.5%

Treatment target for most non-pregnant adults: A1C under 7%. Individualize tighter (6.5%) or looser (8%) based on age, comorbidities, and hypoglycemia risk.

Insulin timing and teaching

Know onset, peak, and duration well enough to anticipate when the patient is at highest hypoglycemia risk. For a printable side-by-side, see the insulin types chart.

• Rapid-acting (lispro, aspart, glulisine): Onset 10–30 min, peak 30 min–3 hr, duration 3–5 hr. Give 15 minutes before a meal — or immediately before — and make sure the meal is coming.
• Short-acting (regular): Onset 30–60 min, peak 2–4 hr, duration 5–8 hr. Give 30 minutes before a meal. Regular is the insulin given IV — it is the standard for DKA and critical-care drips and the expected IV answer on the NCLEX. (Lispro and aspart also carry FDA labeling for IV use, but regular is the choice to pick.)
• Intermediate-acting (NPH): Onset 1–2 hr, peak 4–12 hr, duration 12–18 hr. Cloudy appearance. When mixing with regular, draw up clear before cloudy (regular before NPH).
• Long-acting (glargine, detemir, degludec): Onset 1–2 hr, no pronounced peak, duration 20–24 hr (degludec up to 42 hr). Provides basal coverage. Do not mix with other insulins.

Injection teaching

• Rotate sites within an anatomical area (abdomen, thigh, arm, buttocks); abdomen has the most predictable absorption.
• Store unopened insulin in the refrigerator; in-use vials can be kept at room temperature for 28 days (check the specific product).
• Check glucose before meals and at bedtime (or per regimen). Teach sick-day management — do not stop insulin just because the patient is not eating.
• Always confirm dose with a second RN for high-alert medications per facility policy.

DKA vs HHS

Both are hyperglycemic emergencies; the mechanism, labs, and priorities differ. For a deeper side-by-side, see the dedicated DKA vs HHS comparison.

Diabetic ketoacidosis (DKA)

• Population: More common in type 1; can occur in type 2 under severe stress.
• Glucose: Typically 250–600 mg/dL.
• pH: Under 7.3 (metabolic acidosis).
• Ketones: Positive in serum and urine.
• Presentation: Kussmaul respirations, fruity breath, nausea/vomiting, abdominal pain, dehydration, altered mental status.

Hyperosmolar hyperglycemic state (HHS)

• Population: More common in type 2 and older adults.
• Glucose: Often over 600 mg/dL, can exceed 1,000.
• pH: Usually over 7.3 (minimal acidosis because some insulin is present).
• Ketones: Minimal or absent.
• Presentation: Profound dehydration, altered mental status, seizures. Onset is slower than DKA.

Priority treatment sequence for both

1. Fluids first — isotonic NS (0.9%) to restore volume, typically 1 L in the first hour, then adjust. Switch to 0.45% NS once volume is restored in many protocols.
2. Insulin drip — regular insulin IV infusion after initial fluid bolus. Target glucose reduction of about 50–75 mg/dL/hour.
3. Potassium — hold insulin if K+ is under 3.3 mEq/L; replace first. Insulin drives K+ into cells and can precipitate fatal hypokalemia. (The 2024 ADA/EASD hyperglycemic-crises consensus moved this hold threshold to under 3.5 mEq/L; 3.3 remains the value taught in nursing texts and expected on the NCLEX.)
4. Add dextrose to the IV fluid when glucose reaches ~200–250 mg/dL to prevent hypoglycemia while the insulin drip continues to close the anion gap.
5. Identify and treat the trigger — infection, missed insulin, MI, pancreatitis.

Hypoglycemia: the rule of 15

Hypoglycemia is glucose under 70 mg/dL. Symptoms include diaphoresis, tremors, tachycardia, anxiety, hunger, confusion, and eventually seizures and loss of consciousness. Beta-blockers can mask the early adrenergic warning signs.

Awake, able to swallow

1. Give 15 grams of fast-acting carbohydrate: 4 oz juice or regular soda, 3–4 glucose tablets, 1 tablespoon honey or sugar.
2. Recheck glucose in 15 minutes.
3. If still under 70, repeat. Once above 70, give a snack or meal with protein and complex carbohydrate.

Unconscious or unable to swallow

• IV access available: 25–50 mL of D50W (dextrose 50%) IV push.
• No IV access: glucagon 1 mg IM or SQ (or intranasal glucagon). Turn the patient to the side — glucagon often causes vomiting.

Thyroid disorders

Hyperthyroidism and thyroid storm

• Graves disease is the most common cause of hyperthyroidism. Findings: weight loss despite increased appetite, heat intolerance, tachycardia, tremor, diarrhea, exophthalmos, goiter.
• Thyroid storm is a life-threatening exacerbation — temperature over 38.5°C (101.3°F), severe tachycardia or AFib, agitation, delirium. Treatment: propranolol (controls cardiac symptoms), propylthiouracil (PTU) or methimazole (blocks hormone synthesis), iodine (given at least one hour after PTU to block hormone release), hydrocortisone (reduces T4-to-T3 conversion), cooling measures, and treatment of the trigger (often infection or surgery).
• Teach patients on antithyroid meds to report sore throat, fever, or mouth sores (agranulocytosis risk).

Hypothyroidism and myxedema coma

• Hashimoto thyroiditis is the most common cause. Findings: fatigue, weight gain, cold intolerance, bradycardia, constipation, dry skin, hair loss, depression.
• Myxedema coma is the life-threatening extreme — hypothermia, hypoventilation, hypotension, hyponatremia, altered mental status. Treatment: maintain a patent airway and support ventilation first (hypoventilation is common; mechanical ventilation may be needed), then IV hydrocortisone (100 mg IV, given before thyroid hormone — raising the metabolic rate with levothyroxine can precipitate adrenal crisis if unrecognized adrenal insufficiency is present), then IV levothyroxine and passive rewarming.
• Teach levothyroxine patients: take in the morning on an empty stomach, 30–60 minutes before food. Do not take with calcium, iron, or antacids (absorption interference). Lifelong therapy.

Adrenal disorders

Addison disease (adrenal insufficiency)

• Insufficient cortisol and aldosterone. Findings: fatigue, weight loss, hypotension, hyperpigmentation (primary Addison), salt craving, hyponatremia, hyperkalemia, hypoglycemia.
• Addisonian crisis is an emergency — severe hypotension, shock, hyperkalemia, hypoglycemia, often triggered by infection, surgery, or abrupt steroid withdrawal. Treatment: IV hydrocortisone (100 mg bolus, then continuous infusion or q6h), IV fluids with dextrose, electrolyte correction.
• Teach: never stop steroids abruptly, double the dose during illness (“sick day rules”), carry medical identification, keep injectable hydrocortisone at home.

Cushing syndrome (cortisol excess)

• Excess cortisol — either endogenous (pituitary adenoma = Cushing disease, adrenal tumor, ectopic ACTH) or exogenous (chronic glucocorticoid therapy, the most common cause).
• Findings: central (truncal) obesity, moon face, buffalo hump, purple striae, thin extremities, easy bruising, hyperglycemia, hypertension, hypokalemia, osteoporosis, infection risk, mood changes.
• Nursing priorities: protect from infection, monitor glucose, fall prevention (osteoporosis), skin integrity, emotional support.
• Chronic steroid patients: teach infection precautions, take with food to reduce GI upset, do not stop abruptly (adrenal suppression), weight and glucose monitoring.

Pituitary: SIADH and DI

• SIADH (syndrome of inappropriate ADH): Too much ADH → water retention → dilutional hyponatremia. Findings: concentrated urine, low serum sodium, low serum osmolality, weight gain without edema, seizures if severe. Treatment: fluid restriction, hypertonic saline (3%) for severe hyponatremia — correct slowly (no faster than 8–12 mEq/L in 24 hours to avoid central pontine myelinolysis).
• Diabetes insipidus (DI): Too little ADH (central) or kidney resistance (nephrogenic) → massive dilute urine output, dehydration, hypernatremia, intense thirst. Treatment for central DI: desmopressin (DDAVP). Monitor I&O, daily weights, electrolytes.

Putting it together on test day

1. Identify the hormone imbalance. Too much or too little? What does that hormone normally do?
2. Check glucose first in any altered patient on insulin or an oral hypoglycemic. Hypoglycemia mimics stroke, intoxication, and psychiatric emergencies.
3. In DKA/HHS, fluids before insulin, potassium before insulin if K+ under 3.3.
4. In thyroid and adrenal crises, know the medications cold. Propranolol, PTU, iodine, hydrocortisone for thyroid storm. Hydrocortisone and fluids for Addisonian crisis. Hydrocortisone first, then levothyroxine, for myxedema coma.
5. For teaching questions, favor the answer that prevents a crisis — sick-day rules, site rotation, never stopping basal insulin or steroids abruptly.

Pair this review with your lab values reference for glucose, A1C, TSH, and sodium ranges, and the pharmacology review for insulin, thyroid, and steroid medications. For item-type strategy, see the NGN question types guide.

Frequently Asked Questions

What is the difference between DKA and HHS?

Both are hyperglycemic emergencies, but DKA involves ketones and metabolic acidosis (pH under 7.3) and is more common in type 1 diabetes, with glucose typically 250–600 mg/dL. HHS has minimal or absent ketones and little acidosis (pH usually over 7.3) because some insulin is still present; it is more common in type 2 diabetes and older adults, with glucose often over 600 mg/dL and sometimes exceeding 1,000. Both are treated with fluids first, then an insulin drip, with potassium replaced before insulin if K+ is under 3.3 mEq/L.

Why do you give fluids before insulin in DKA?

The patient is profoundly volume-depleted. Giving insulin without first restoring volume drops the glucose too fast and can leave the patient hypotensive and hypokalemic. Isotonic normal saline (0.9%) is started first — typically 1 L in the first hour — before the regular insulin IV infusion begins.

When does insulin cause the highest risk of hypoglycemia?

The peak of each insulin is when hypoglycemia risk is highest. Rapid-acting insulin peaks about 30 minutes to 3 hours after the dose, short-acting (regular) peaks about 2–4 hours, and NPH peaks about 4–12 hours. Long-acting basal insulins such as glargine, detemir, and degludec have no pronounced peak. Knowing onset, peak, and duration lets you anticipate when to watch for hypoglycemia and when meals must be available.

How do you treat hypoglycemia using the rule of 15?

If the patient is awake and able to swallow, give 15 grams of fast-acting carbohydrate (such as 4 oz of juice or regular soda, 3–4 glucose tablets, or 1 tablespoon of honey or sugar), recheck glucose in 15 minutes, and repeat if it is still under 70 mg/dL. Once glucose is above 70, give a snack or meal with protein and complex carbohydrate. If the patient is unconscious or cannot swallow, give 25–50 mL of D50W IV if access is available, or glucagon 1 mg IM/SQ (or intranasal) if there is no IV access.

Why is potassium replaced before insulin when K+ is low?

Insulin drives potassium into the cells, which lowers serum potassium. If K+ is already under 3.3 mEq/L, starting insulin first can cause life-threatening hypokalemia and dysrhythmias. The rule is to hold insulin and replace potassium first, then start the insulin drip once K+ is above 3.3 mEq/L.