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NCLEX fluid and electrolyte practice questions

20 free NCLEX-style fluid and electrolyte questions: potassium, sodium, calcium and magnesium imbalances, IV fluid choices, potassium safety rules and blood transfusions, with rationales.

Tap an answer to check it, or open "Show the answer and rationale" under each question. Every client is fictional. For exam practice only, not medical advice.

Question 1 of 20

A client receiving a 3-in-1 parenteral nutrition admixture at 80 mL/hr through a PICC returns from a 3-hour procedure, and the nurse finds that the infusion was paused the entire time. The 1,920-mL bag was hung 5 hours ago. Which action should the nurse take?

  1. Restart the PN at 120 mL/hr for 6 hours to make up the missed 240 mL
  2. Restart the PN at 80 mL/hr and report the missed volume to the provider
  3. Hang dextrose 10% at 80 mL/hr until a fresh PN bag arrives
  4. Restart the PN at 80 mL/hr and leave the bag up until it is empty
Show the answer and rationale

Answer: B

PN runs at the prescribed rate even when it falls behind, because speeding up delivers a dextrose load that can cause hyperglycemia and osmotic diuresis, and any rate change needs a prescription; the nurse restarts at 80 mL/hr, reports the missed volume and checks the glucose, since a 3-hour pause can lower it. The catch-up rate is the runner-up because the arithmetic is right, 40 extra mL/hr × 6 hours = 240 mL, but it is exactly what PN protocols forbid. Dextrose 10% is the bridge when no PN is available, not when the bag is still usable, and a lipid-containing admixture is completed within 24 hours of hanging, so the bag is not kept up past that to finish it.

📚 Learn it: IV Fluids, Potassium Rules and the First 15 Minutes of a Transfusion

Question 2 of 20

A nurse is assessing a client with bulimia nervosa who reports self-induced vomiting several times a day. Which finding requires immediate follow-up?

  1. Swollen parotid glands and an elevated serum amylase
  2. Dry mouth and a serum bicarbonate of 32 mEq/L
  3. Irregular pulse and a potassium of 2.8 mEq/L
  4. Calluses over the knuckles of the dominant hand
Show the answer and rationale

Answer: C

Repeated vomiting depletes potassium, and a level of 2.8 mEq/L (normal about 3.5 to 5.0) with an irregular pulse signals a risk of life-threatening dysrhythmias that needs immediate treatment. A bicarbonate of 32 mEq/L, well above normal, shows the metabolic alkalosis that loss of stomach acid causes and needs correcting, but by itself it is less immediately dangerous than low potassium with an irregular pulse. Swollen parotid glands with a raised amylase and calluses on the knuckles from inducing vomiting are expected signs of purging. They are addressed in the ongoing plan, but they do not threaten the client's life today.

📚 Learn it: Potassium: The Electrolyte That Stops Hearts

Question 3 of 20

A client who has taken omeprazole 40 mg daily for 3 years reports muscle cramps and tremors, and the ECG shows a prolonged QT interval. Which laboratory result should the nurse expect?

  1. Serum magnesium of 1.1 mg/dL
  2. Serum vitamin B12 of 150 pg/mL
  3. Serum sodium of 129 mEq/L
  4. Serum calcium of 11.2 mg/dL
Show the answer and rationale

Answer: A

Proton pump inhibitors taken for 3 months or longer, most often after more than a year, can cause hypomagnesemia, which brings muscle cramps, tremors, tetany and arrhythmias, including a prolonged QT interval, and often lowers calcium and potassium as well. Daily use for longer than about 3 years can also lower vitamin B12, which makes that result tempting, but a low B12 causes anemia and numbness rather than tetany or a long QT. A high calcium shortens rather than prolongs the QT interval, and a low sodium mainly causes headache and confusion and is not a typical cause of a prolonged QT.

📚 Learn it: Sodium, Calcium and Magnesium: Twitching, Seizing and Going Flat

Question 4 of 20

A client with a liver laceration has received 10 units of packed red blood cells and 6 units of plasma over 3 hours. The client now has tingling around the mouth, muscle twitching, a prolonged QT interval, and a blood pressure that keeps falling despite the transfusions. Which prescription should the nurse anticipate?

  1. IV norepinephrine, titrated to the MAP
  2. IV potassium chloride, guided by potassium levels
  3. IV calcium, guided by ionized calcium levels
  4. IV sodium bicarbonate, guided by the ABG
Show the answer and rationale

Answer: C

Stored blood products contain citrate, which binds calcium to keep them from clotting; when many units are given quickly, especially to a client whose injured liver clears citrate slowly, the ionized calcium falls, causing perioral tingling, twitching, a prolonged QT interval, and hypotension from weakened heart contraction. IV calcium is given as prescribed and adjusted to ionized calcium levels. Potassium is the closest distractor, because low potassium can also affect the QT interval, but it does not correct the cause and can be dangerous, because stored red cells already add potassium. Norepinephrine does not correct the low calcium that is weakening the heart, and bicarbonate does not address the calcium and, by raising the pH, can lower the ionized calcium further.

📚 Learn it: IV Fluids, Potassium Rules and the First 15 Minutes of a Transfusion

Question 5 of 20

The telemetry technician calls the nurse about four clients whose morning potassium levels are elevated. Which client should the nurse see first?

  1. Potassium 5.8 mEq/L with a normal ECG, in a client due for dialysis this afternoon
  2. Potassium 6.2 mEq/L with a QRS widened from 0.08 to 0.14 seconds, after a crush injury
  3. Potassium 6.6 mEq/L with tall, peaked T waves, in a client with chronic kidney disease
  4. Potassium 5.6 mEq/L before an insulin infusion starts, in a client with DKA
Show the answer and rationale

Answer: B

A widening QRS is a late sign of hyperkalemia: the ECG moves from peaked T waves to a longer PR interval and flattened P waves, then a wide QRS that can merge into a sine wave and ventricular fibrillation. The crush-injury client is closest to arrest despite the lower number, and damaged muscle keeps releasing potassium. The client with 6.6 mEq/L and peaked T waves is the tempting choice and needs prompt treatment too, but peaked T waves are the earliest change. A level of 5.6 mEq/L is expected in DKA before insulin, and 5.8 mEq/L with a normal ECG can wait for scheduled dialysis.

📚 Learn it: Potassium: The Electrolyte That Stops Hearts

Question 6 of 20

An 81-year-old client started hydrochlorothiazide for hypertension 2 weeks ago. The client's daughter reports that over the past 2 days the client has become confused and unsteady on her feet. Which laboratory result best explains these findings?

  1. Serum potassium of 2.9 mEq/L
  2. Serum magnesium of 1.1 mg/dL
  3. Fasting blood glucose of 214 mg/dL
  4. Serum sodium of 123 mEq/L
Show the answer and rationale

Answer: D

Thiazide diuretics are a leading cause of hyponatremia in older adults, often within the first weeks of therapy, and a sodium of 123 mEq/L best explains new confusion and unsteadiness and raises fall risk. The runner-up is the potassium of 2.9 mEq/L, another thiazide loss, but low potassium mainly causes muscle weakness, cramps and rhythm problems rather than confusion. A magnesium of 1.1 mg/dL is also wasted by thiazides and causes weakness and tremor, and a glucose of 214 mg/dL reflects the drug's effect on blood sugar but is not high enough alone to explain an acute mental status change.

📚 Learn it: Sodium, Calcium and Magnesium: Twitching, Seizing and Going Flat

Question 7 of 20

At 1000, a provider inserts a triple-lumen central venous catheter in a client's right subclavian vein at the bedside. A chest x-ray is taken at 1015 but has not yet been read. At 1030, the client's first bag of parenteral nutrition arrives from the pharmacy. Which action should the nurse take?

  1. Wait to start the PN until the x-ray confirms the tip position
  2. Start the PN through the distal lumen after confirming a blood return
  3. Start the PN at half the prescribed rate until the x-ray is read
  4. Infuse the PN through the client's peripheral IV until the x-ray is read
Show the answer and rationale

Answer: A

A central line placed at the bedside is released for use only after its tip position is confirmed, here by the chest x-ray being read; a subclavian insertion can also cause a pneumothorax, which the same film shows, and a misplaced tip can send hyperosmolar PN into the wrong vessel. A blood return is the runner-up because it shows the catheter is in a vein, but not where the tip lies. Half the rate still puts PN through an unconfirmed line, and PN made for a central line is too concentrated for a peripheral vein.

📚 Learn it: IV Fluids, Potassium Rules and the First 15 Minutes of a Transfusion

Question 8 of 20

A client admitted for cellulitis has no history of kidney disease and had a potassium of 4.1 mEq/L yesterday. Today the laboratory calls a potassium of 6.7 mEq/L and notes that the specimen was moderately hemolyzed. The client has no complaints, and the cardiac monitor shows sinus rhythm with normal T waves. Which action should the nurse take first?

  1. Give IV calcium gluconate per the hyperkalemia protocol
  2. Obtain a 12-lead ECG and a repeat potassium level
  3. Disregard the result, because hemolysis makes it invalid
  4. Call the rapid response team for a potassium above 6.5
Show the answer and rationale

Answer: B

Hemolysis releases potassium from broken red cells into the tube, so a sudden high result in a well client with normal kidneys and no ECG changes is probably false. It is confirmed rather than assumed: a 12-lead ECG and a repeat level settle the question quickly. Disregarding the result is the runner-up; it is usually right about the cause, but it would miss a true rise. Calcium gluconate is given for hyperkalemia with ECG changes, which this client does not have, and a stable client with a normal rhythm does not need a rapid response call.

📚 Learn it: Potassium: The Electrolyte That Stops Hearts

Question 9 of 20

Forty minutes into a unit of packed red blood cells, a 52-year-old client reports itching, and the nurse sees raised hives on the chest and arms. Temperature 98.8°F (37.1°C), unchanged; BP 128/76 mm Hg; HR 84 beats/min; RR 16 breaths/min; SpO2 98% on room air. The lungs are clear, and the client denies throat tightness. Which action should the nurse take first?

  1. Stop the transfusion
  2. Give the prescribed diphenhydramine and slow the transfusion rate
  3. Give epinephrine IM from the anaphylaxis kit
  4. Send the unit, tubing and a urine specimen to the blood bank
Show the answer and rationale

Answer: A

Hives and itching alone, with stable vital signs and no breathing or throat symptoms, are a mild allergic reaction, but every suspected reaction starts with stopping the transfusion and keeping IV access open. Diphenhydramine is the runner-up: it is the next step, and a mild urticarial reaction is the one type in which the same unit may be restarted if the hives resolve and the provider agrees, but the transfusion is paused first. Epinephrine is for anaphylaxis with airway or blood pressure involvement, and returning the unit with a urine specimen belongs to the workup of a hemolytic reaction, which hives alone usually do not need.

📚 Learn it: IV Fluids, Potassium Rules and the First 15 Minutes of a Transfusion

Question 10 of 20

A client with heart failure has a serum potassium of 6.1 mEq/L on the morning laboratory report. Which of the client's 0900 medications should the nurse hold and discuss with the provider?

  1. Furosemide 40 mg by mouth
  2. Spironolactone 25 mg by mouth
  3. Dapagliflozin 10 mg by mouth
  4. Metoprolol succinate 50 mg by mouth
Show the answer and rationale

Answer: B

Spironolactone blocks aldosterone, so the kidneys hold on to potassium, and a level of 6.1 mEq/L puts the client at risk for life-threatening arrhythmias; the dose is held and the provider notified, and an ECG and a repeat potassium level are likely. Furosemide is the tempting choice because it is a diuretic, but it lowers potassium and is usually continued. Dapagliflozin and metoprolol are not the cause of this result.

📚 Learn it: Potassium: The Electrolyte That Stops Hearts

Practice 10 more Fluids & electrolytes questions free →

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Question 11 of 20

A nurse is supervising a newly licensed nurse who is preparing to start a transfusion of packed red blood cells. Which action by the newly licensed nurse requires intervention?

  1. Hanging the unit as soon as it arrives from the blood bank, without a blood warmer
  2. Staying with the client for the first 15 minutes of the transfusion
  3. Starting the unit through a 22-gauge catheter in the client's forearm
  4. Planning to hang dextrose 5% in water if the transfusion slows
Show the answer and rationale

Answer: D

Dextrose 5% in water makes red cells swell, clump and hemolyze, so only 0.9% sodium chloride is used with blood, including when a transfusion slows. A 22-gauge catheter may look too small, but it is acceptable for a routine adult transfusion, with larger catheters used for rapid infusion. Blood is hung promptly once it arrives from the blood bank, and a blood warmer is needed only for rapid or massive transfusion or for certain conditions such as cold agglutinins. Staying with the client for the first 15 minutes, when most acute reactions appear, is correct.

📚 Learn it: IV Fluids, Potassium Rules and the First 15 Minutes of a Transfusion

Question 12 of 20

A client with end-stage kidney disease who missed dialysis had a potassium of 6.9 mEq/L and received IV calcium gluconate, then regular insulin 10 units IV with 25 g of dextrose at 0900. At 1030 the client is sweaty, shaky, and confused. The capillary glucose is 52 mg/dL, the monitor shows sinus rhythm with less-peaked T waves, and a repeat potassium is 5.9 mEq/L. Which action should the nurse take first?

  1. Give a second dose of insulin and dextrose
  2. Ask the dialysis unit to start treatment now
  3. Repeat the calcium gluconate dose
  4. Give IV dextrose as the protocol directs
Show the answer and rationale

Answer: D

Insulin moves potassium into cells but also lowers glucose, and about one client in six becomes hypoglycemic 1 to 3 hours after the dose; kidney failure slows insulin clearance and adds to the risk. A glucose of 52 mg/dL with confusion is the immediate threat to the brain, so IV dextrose comes first, and glucose is checked hourly for at least 4 to 6 hours. Dialysis is the runner-up: it is still needed to remove potassium, but a level of 5.9 mEq/L with improving T waves is no longer the emergency. Improving ECG changes do not call for more calcium, and more insulin would deepen the low glucose.

📚 Learn it: Potassium: The Electrolyte That Stops Hearts

Question 13 of 20

A client with a PICC in the right upper arm has 0.9% sodium chloride infusing at 75 mL/hr. The pump alarms for a downstream occlusion, and when the nurse tries to flush the lumen there is resistance and no blood return. Which action should the nurse take first?

  1. Check for a closed clamp or kinked tubing and reposition the arm
  2. Flush with more force to push the clot through the catheter
  3. Remove the PICC and request a new peripheral IV
  4. Instill alteplase into the lumen as the occlusion protocol directs
Show the answer and rationale

Answer: A

Simple mechanical causes are ruled out first: the nurse looks for a closed clamp, kinked tubing or a tight dressing and has the client raise and lower the arm, take a deep breath or cough, which can free a catheter tip resting against the vein wall. Alteplase is the runner-up: it treats a clot once mechanical causes are excluded, under the protocol. A catheter that resists is never forced, because the pressure can rupture it, and removing the PICC skips the simple fixes and gives up central access the client needs.

📚 Learn it: IV Fluids, Potassium Rules and the First 15 Minutes of a Transfusion

Question 14 of 20

A nurse is reviewing potassium replacement prescriptions for four adults with hypokalemia, each with adequate urine output. Which prescription should the nurse question?

  1. Potassium chloride 20 mEq orally twice daily with meals and water
  2. Potassium chloride 40 mEq in 100 mL IV over 1 hour by peripheral line
  3. Potassium chloride 40 mEq in 250 mL IV over 4 hours by central line with ECG monitoring
  4. Potassium chloride 10 mEq in 100 mL IV over 1 hour by peripheral line
Show the answer and rationale

Answer: B

Forty mEq in 100 mL over 1 hour runs at 40 mEq/hr in a concentration of 400 mEq/L, which the label reserves for a central line with continuous ECG monitoring in severe, urgent hypokalemia; through a peripheral vein it causes pain and phlebitis and risks fatal arrhythmias. The runner-up is the other 40 mEq prescription, but spread over 4 hours through a central line with ECG monitoring it delivers 10 mEq/hr and is an accepted way to replace potassium. Ten mEq over 1 hour is the usual peripheral limit, and oral potassium taken with food and water protects the stomach.

📚 Learn it: IV Fluids, Potassium Rules and the First 15 Minutes of a Transfusion

Question 15 of 20

A nurse is caring for four clients who are receiving blood products. Which client should the nurse see first?

  1. A client 20 minutes into a unit of platelets who has shaking chills, a temperature of 102.6°F (39.2°C) and a BP of 86/50 mm Hg
  2. A client with heart failure who is finishing a first unit of packed red cells and whose BP has risen from 128/74 to 140/80 mm Hg, with no shortness of breath
  3. A client 25 minutes into a unit of plasma who has three small, itchy hives on one forearm
  4. A client 2 hours into a unit of packed red cells whose temperature has gone from 98.4°F (36.9°C) to 99.0°F (37.2°C)
Show the answer and rationale

Answer: A

Rigors, a high fever and a falling blood pressure 20 minutes into platelets suggest a septic transfusion reaction: platelets are stored at room temperature, so bacteria in a contaminated unit can multiply enough to cause septic shock, and this client needs the transfusion stopped and urgent treatment. The heart failure client is the runner-up, since a rising blood pressure can be an early sign of circulatory overload, but a 12-point rise with no shortness of breath calls for close monitoring of breathing, lung sounds and oxygen saturation before any second unit, not emergency care. A few hives are a mild allergic reaction to handle next, and a 0.6°F rise with no other symptoms is watched.

📚 Learn it: IV Fluids, Potassium Rules and the First 15 Minutes of a Transfusion

Question 16 of 20

A client is receiving vinorelbine, a vesicant, through a peripheral IV in the forearm. Partway through the dose, the client reports burning at the site, and the nurse sees swelling around the catheter. The nurse stops the infusion. Which action should the nurse take next?

  1. Apply an ice pack to the site for 15 to 20 minutes
  2. Leave the catheter in and slowly aspirate any remaining drug
  3. Remove the catheter and apply firm pressure to the site
  4. Flush the catheter with 0.9% sodium chloride to dilute the drug
Show the answer and rationale

Answer: B

After the infusion is stopped, the ONS/ASCO extravasation guideline leaves the catheter in place so any remaining drug can be slowly aspirated through it, without flushing; the cannula is then removed without firm pressure on the site. Removing the catheter is the runner-up: it comes next, but done first it leaves drug in the line and tissue that could have been withdrawn, and firm pressure spreads the drug. Flushing pushes more vesicant into the tissue. Cold compresses are used for most vesicants, but vinca alkaloids such as vinorelbine get warm compresses, which disperse the drug, along with hyaluronidase injected subcutaneously around the site as the antidote.

📚 Learn it: IV Fluids, Potassium Rules and the First 15 Minutes of a Transfusion

Question 17 of 20

A client's parenteral nutrition bag runs dry at 0200, and the pharmacy cannot deliver the next bag until 0600. Which action should the nurse take?

  1. Run the new bag at double the rate once it arrives
  2. Hang 0.9% sodium chloride at the nutrition rate
  3. Hang dextrose 10% in water at the nutrition rate
  4. Flush the lumen and lock it until the bag arrives
Show the answer and rationale

Answer: C

Parenteral nutrition supplies concentrated dextrose, and the pancreas is releasing insulin to match it, so stopping it suddenly can cause rebound hypoglycemia; dextrose 10% at the same rate bridges the gap until the new bag arrives. Normal saline or a locked line provides no glucose, and running the new bag faster to catch up causes hyperglycemia and fluid overload.

📚 Learn it: IV Fluids, Potassium Rules and the First 15 Minutes of a Transfusion

Question 18 of 20

A client has had a nasogastric tube to low intermittent suction for 3 days after a bowel resection. Which laboratory result should the nurse report first?

  1. Sodium 137 mEq/L
  2. Hemoglobin 11.8 g/dL
  3. Potassium 2.9 mEq/L
  4. Bicarbonate 29 mEq/L
Show the answer and rationale

Answer: C

Gastric suction removes potassium and hydrochloric acid, and a potassium of 2.9 mEq/L can cause dangerous dysrhythmias, muscle weakness, and a further delay in the return of bowel function, so it is the priority to report. A bicarbonate of 29 mEq/L reflects the mild metabolic alkalosis that gastric losses produce and is corrected along with the potassium, but it is not immediately life-threatening. A sodium of 137 mEq/L is normal, and a hemoglobin of 11.8 g/dL is a modest, expected drop after surgery.

📚 Learn it: Potassium: The Electrolyte That Stops Hearts

Question 19 of 20

A client receiving IV haloperidol for delirium and IV ondansetron for nausea has a QTc of 590 ms and a potassium of 3.2 mEq/L. The monitor shows repeated short runs of polymorphic ventricular tachycardia that twist around the baseline and stop on their own; between runs, the client is alert with a blood pressure of 112/70 mm Hg. Which medication should the nurse prepare to administer?

  1. Amiodarone 150 mg IV infused over 10 minutes
  2. Procainamide by continuous IV infusion
  3. Adenosine 6 mg IV push followed by a saline flush
  4. Magnesium sulfate 2 g IV over 15 minutes
Show the answer and rationale

Answer: D

Polymorphic ventricular tachycardia that twists around the baseline in a client with a long QT interval is torsades de pointes, and IV magnesium sulfate is the treatment of choice, along with correcting the potassium and stopping QT-prolonging drugs such as haloperidol and ondansetron; if the client loses a pulse, the rhythm is treated with defibrillation and CPR. Amiodarone and procainamide lengthen the QT interval further and can make torsades worse. Adenosine acts on the AV node and does not treat ventricular rhythms.

📚 Learn it: Sodium, Calcium and Magnesium: Twitching, Seizing and Going Flat

Question 20 of 20

A nurse is giving morphine 4 mg IV push through the port of a running maintenance infusion of 0.9% sodium chloride. Which action is correct?

  1. Inject the dose rapidly so it reaches the client before the fluid dilutes it
  2. Use the injection port closest to the IV bag so the drug mixes with more fluid
  3. Pinch the tubing above the port and inject slowly over the recommended time
  4. Stop the maintenance fluid for 30 minutes afterward to prevent dilution
Show the answer and rationale

Answer: C

Pinching the tubing above the port keeps the drug from flowing back toward the bag, and opioids are pushed slowly over the time the drug reference lists while respirations are watched, because a rapid IV push of morphine can cause apnea and a sharp drop in blood pressure. The port closest to the client is used so the dose arrives promptly, and stopping the maintenance fluid serves no purpose and can let the catheter clot.

📚 Learn it: IV Fluids, Potassium Rules and the First 15 Minutes of a Transfusion

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