Free practice questions · Lab values
Lab values practice questions.
Electrolytes, blood counts, coagulation and renal values, and what a result means for the next action. Ten questions from the Lumen Nursing NCLEX-RN bank. Answer each one and check it; the rationale explains the key and every other option.
1Multiple choice, single answerCritical Care
On day 6 after coiling of a ruptured aneurysm, a 49-year-old client's serum sodium has fallen from 139 to 129 mEq/L over 2 days. The urine output has been 3,000 to 3,500 mL a day, the weight has dropped 1.5 kg, and the mucous membranes are dry. The client is alert and oriented. Which prescription should the nurse question?
Give fludrocortisone 0.1 mg orally twice a day
Restrict all oral and IV fluids to 1,000 mL a day
Infuse 0.9% sodium chloride IV continuously at 125 mL/hr
Check the serum sodium level every 6 hours
Answer it, then check it.
Answer and rationale
Answer
- B: Restrict all oral and IV fluids to 1,000 mL a day
The key, and why
Hyponatremia is common after a subarachnoid hemorrhage, and it usually comes from one of two causes. Cerebral salt wasting is a loss of sodium in the urine that takes water with it, so the client becomes dry, loses weight, and passes a large volume of urine. The syndrome of inappropriate antidiuretic hormone (SIADH) holds water instead, so the client is not dry and the urine output is low.
This client has the cerebral salt wasting picture: a high urine output, weight loss, and dry mucous membranes. Fluid restriction would make the client more dehydrated. In a client who is in the window for cerebral vasospasm, low blood volume reduces blood flow through narrowed vessels and raises the risk of a delayed stroke. Fluid restriction is avoided after a subarachnoid hemorrhage, so the nurse questions it.
Each distractor
Option A is a mineralocorticoid that helps the kidney hold on to sodium, and it is used for salt wasting after a subarachnoid hemorrhage.
Option C replaces the lost volume and sodium with an isotonic fluid, which is the treatment.
Option D is appropriate. The sodium is checked often, both to catch a further fall and to make sure it is not corrected too fast.
The teaching point
CEREBRAL SALT WASTING = sodium LOW, urine output HIGH, client DRY, weight DOWN. Treat = sodium and FLUID. SIADH = sodium LOW, urine output LOW, client NOT dry. Usual treatment = fluid restriction. After SAH = NO fluid restriction. Low volume worsens VASOSPASM.
Safety note
Restricting fluid in a client with salt wasting after a subarachnoid hemorrhage can lead to a delayed ischemic stroke.
2Multiple choice, single answerCritical Care
Two days after a laparoscopic cholecystectomy, a 52-year-old client with type 2 diabetes who takes metformin and empagliflozin at home has eaten very little. The client reports nausea and abdominal pain and is breathing deeply at 28/min. Laboratory results are glucose 212 mg/dL, pH 7.18, bicarbonate 11 mEq/L, anion gap 24 mEq/L, and serum beta-hydroxybutyrate 5.8 mmol/L. Which condition should the nurse suspect?
Diabetic ketoacidosis linked to empagliflozin and poor oral intake
Starvation ketosis expected after fasting for the cholecystectomy
Lactic acidosis caused by metformin taken during the recovery period
Hyperosmolar hyperglycemic state triggered by the stress of surgery
Answer it, then check it.
Answer and rationale
Answer
- A: Diabetic ketoacidosis linked to empagliflozin and poor oral intake
The key, and why
Diabetic ketoacidosis is a shortage of insulin severe enough that the body burns fat for fuel, and the fat breakdown makes ketoacids faster than the kidneys can clear them. The blood turns acidic, the bicarbonate is used up buffering the acid, and the anion gap opens.
Empagliflozin is a sodium-glucose cotransporter 2 (SGLT2) inhibitor. It lowers glucose by making the kidneys spill glucose into the urine. That means a client can be in full ketoacidosis while the glucose sits near 200 mg/dL, which is why this form is called euglycemic DKA and why it gets missed. Surgery, fasting, and a reduced insulin effect are the usual triggers.
The numbers here are ketoacidosis without question. A pH of 7.18, a bicarbonate of 11, a gap of 24, and a beta-hydroxybutyrate of 5.8 mmol/L (anything over 3 is significant) all point the same way. The nurse reports it, expects the empagliflozin to be stopped, and expects fluids and an insulin infusion with dextrose, because the insulin is needed to stop ketone production even though the glucose is not high.
Each distractor
Option B, starvation ketosis, makes small amounts of ketones with a normal or near-normal pH and a bicarbonate of 18 or more. It does not drop the pH to 7.18.
Option C, metformin lactic acidosis, raises the lactate, not the ketones. It is more likely with kidney failure or shock, and a beta-hydroxybutyrate of 5.8 points to ketoacids.
Option D, hyperosmolar hyperglycemic state, brings a glucose usually over 600 mg/dL, an osmolality over 320 mOsm/kg, and little or no ketoacidosis. This glucose is 212 and the pH is 7.18.
The teaching point
SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin) can cause DKA with a NEAR-NORMAL glucose. Judge DKA by the pH, bicarbonate, anion gap, and KETONES, not by the glucose alone. These drugs are usually held for 3 days before planned surgery.
3Multiple choice, single answerMaternal and Newborn
Two hours after a vaginal birth, a client with type 2 diabetes who needed 140 units of insulin a day in the third trimester has a capillary glucose of 82 mg/dL. She plans to breastfeed, and her prenatal insulin doses are still active in the medication record. Which action should the nurse take?
Hold the prenatal insulin doses and obtain new orders from the health care provider
Give the full prenatal dose before the next meal to prevent rebound hyperglycemia
Give half of the prenatal dose with the next meal and recheck the glucose in 4 hours
Start an insulin infusion at the prenatal rate until the client is eating her usual diet
Answer it, then check it.
Answer and rationale
Answer
- A: Hold the prenatal insulin doses and obtain new orders from the health care provider
The key, and why
The placenta produces the hormones that oppose insulin. Once it is delivered, those hormones fall quickly, and insulin needs drop sharply, often well below the pre-pregnancy dose for the first days. Breastfeeding uses glucose and lowers the level further. Giving the third-trimester dose to this client could cause severe hypoglycemia. The nurse holds the prenatal doses, reports the reading, obtains revised orders, and checks the glucose often, watching for shakiness, sweating and confusion, especially during and after feedings.
Each distractor
Option B gives a dose sized for the insulin resistance of late pregnancy, which no longer exists.
Option C changes the dose without a prescription. Halving is a guess, and the glucose may need checking more often than every 4 hours.
Option D continues a high insulin rate when the need has fallen sharply.
The teaching point
AFTER DELIVERY = insulin needs FALL SHARPLY. HOLD or REDUCE as prescribed and WATCH for HYPOGLYCEMIA. BREASTFEEDING lowers glucose further.
4Multiple choice, single answerMaternal and Newborn
A client at 32 weeks' gestation with heart disease takes digoxin 0.125 mg and furosemide 20 mg each morning. Before giving the morning doses, the nurse finds an apical pulse of 82/min and a serum potassium of 3.1 mEq/L. Which action should the nurse take?
Give both medications, because the apical pulse is above 60
Give digoxin now and hold furosemide until the next day
Hold the medications and report the potassium level to the provider
Give both medications with a glass of orange juice
Answer it, then check it.
Answer and rationale
Answer
- C: Hold the medications and report the potassium level to the provider
The key, and why
Furosemide causes the kidneys to excrete potassium, and a low potassium makes the heart muscle far more sensitive to digoxin. Even at a normal digoxin dose, a potassium of 3.1 mEq/L can lead to digoxin toxicity and dangerous dysrhythmias. Giving more furosemide would lower the potassium further. The nurse holds the doses and reports the potassium so that the provider can order replacement and decide on the doses.
Each distractor
Option A checks the pulse but ignores the potassium, which is just as important before digoxin.
Option B gives the digoxin while the potassium is low, the combination that causes toxicity.
Option D gives both drugs and relies on orange juice. Juice adds little potassium, too slowly, to correct a level of 3.1, and the furosemide would lower it further.
The teaching point
DIGOXIN + LOW POTASSIUM = TOXICITY risk. Before digoxin, check the APICAL PULSE (hold if under 60 in an adult) and the POTASSIUM. FUROSEMIDE lowers potassium.
5Multiple response, select NNutrition
A 48-year-old client with severe weight loss from an esophageal stricture began parenteral nutrition 2 days ago after eating almost nothing for 3 weeks. Today the client reports new weakness in both arms and feels short of breath when sitting up. The nurse reviews the morning laboratory results. Select the 3 results that require follow-up.
Potassium 3.0 mEq/L
Phosphorus 1.5 mg/dL
Glucose 162 mg/dL
Albumin 3.0 g/dL
Sodium 138 mEq/L
Magnesium 1.2 mg/dL
Answer it, then check it.
Answer and rationale
Answer
- A: Potassium 3.0 mEq/L
- B: Phosphorus 1.5 mg/dL
- F: Magnesium 1.2 mg/dL
The key, and why
A client who has gone weeks with almost no food has used up the phosphorus, potassium, and magnesium stored inside the cells, even when the blood levels look normal before feeding. When nutrition begins, the dextrose raises insulin, and insulin drives these electrolytes back into the cells to build new tissue and make energy. The blood levels fall, usually within the first 2 to 4 days. That is refeeding syndrome.
Low phosphorus starves muscles of ATP, which explains this client's weakness and shortness of breath as the diaphragm tires. Low potassium and low magnesium add the risk of dangerous dysrhythmias. All three are reported now, the rate of the parenteral nutrition is usually reduced, and the electrolytes are replaced before feeding is advanced again.
Each distractor
Option C is within the target for a client on parenteral nutrition, about 140 to 180 mg/dL or lower, so it is monitored rather than reported as urgent.
Option D is low, but albumin changes over weeks, reflects illness and inflammation as much as nutrition, and does not explain a sudden change in strength or breathing.
Option E is a normal sodium.
The teaching point
Refeeding = LOW PHOSPHORUS, LOW POTASSIUM, LOW MAGNESIUM in the first DAYS of feeding. Phosphorus = energy for the DIAPHRAGM and heart. Low = WEAKNESS and RESPIRATORY failure.
6Multiple choice, single answerMaternal and Newborn
A nurse is caring for a term newborn whose total bilirubin is 15 mg/dL on the third day of life. Which action should the nurse anticipate?
Admission for treatment of the bilirubin level
Discharge with a repeat level in one week
No action, because this level is expected on day three
Immediate exchange transfusion
Answer it, then check it.
Answer and rationale
Answer
- A: Admission for treatment of the bilirubin level
The key, and why
In a term newborn, a bilirubin above 12 mg/dL is evaluated, and the point at which health care providers bring these babies in for treatment is around 14 to 15. This one is at that threshold, so the baby is admitted, phototherapy is started and the level is followed.
The reason for admitting at 14 or 15 rather than at 20 is the distance still to travel. Twenty is where bilirubin starts crossing into the brain, and a level that has reached 15 on day three has been climbing. Treating it now is what keeps it away from 20.
In current practice, the American Academy of Pediatrics (2022) sets treatment thresholds by the newborn's age in hours, gestational age, and risk factors rather than by a single bilirubin number.
Each distractor
Option B sends home a baby whose level is rising and checks it after the window in which harm happens.
Option C treats an elevated level as ordinary. Some rise on day two to three is expected, and 15 is too high to simply watch and wait.
Option D is the treatment for a level that has climbed much higher or is not responding, and phototherapy comes first.
The teaching point
NEWBORN bilirubin ELEVATED 10 to 20. Physicians HOSPITALISE at about 14 to 15. TOXICITY above 20, which is where KERNICTERUS begins. ADULT normal is 0.2 to 1.2 mg/dL. Different world.
7Multiple choice, single answerCritical Care
In the intensive care unit, the nurse admits a 72-year-old client with multiple myeloma who has had 4 days of increasing confusion, thirst and constipation. The serum calcium is 14.2 mg/dL, and the creatinine is 1.9 mg/dL (1.0 mg/dL last month). The blood pressure is 98/60 mm Hg, the heart rate is 108/min, and the mucous membranes are dry. The nurse receives the following prescriptions. Which prescription should the nurse implement first?
Furosemide 40 mg IV push now
Zoledronic acid 4 mg IV infusion over 15 minutes
0.9% sodium chloride 1,000 mL IV bolus, then 200 mL/hr
Calcitonin 4 units/kg subcutaneously every 12 hours
Answer it, then check it.
Answer and rationale
Answer
- C: 0.9% sodium chloride 1,000 mL IV bolus, then 200 mL/hr
The key, and why
Hypercalcemia of malignancy is a high serum calcium caused by cancer, either from bone being broken down by the tumor, as in multiple myeloma and bone metastases, or from a hormone the tumor releases. A high calcium damages the kidney's ability to concentrate urine, so the client loses large amounts of water, becomes dehydrated, and the kidneys then clear even less calcium. Confusion, thirst, constipation, a low blood pressure and a rising creatinine all fit that cycle.
Rehydration with 0.9% sodium chloride comes first. It restores the circulating volume and lets the kidneys excrete calcium again, and it starts working within hours. The other drugs build on it.
Each distractor
Option A gives a loop diuretic to a client who is already dry and hypotensive. Furosemide is used only after the volume is restored, and only when fluid overload is a concern.
Option B, zoledronic acid, stops bone from releasing calcium and is part of the plan, but it takes 2 to 4 days to lower the calcium, and it is given after rehydration, with the creatinine checked before each dose.
Option D, calcitonin, lowers the calcium within hours and is often given early, but it is a short-term bridge with a modest effect and does nothing for the dehydration.
The teaching point
HYPERCALCEMIA of malignancy = CONFUSION, THIRST, POLYURIA, CONSTIPATION, dehydration, short QT. Order = IV 0.9% sodium chloride FIRST → calcitonin (fast, short-lived) → bisphosphonate (slow, lasting). Loop diuretic only AFTER rehydration.
8Multiple choice, single answerNutrition
The daughter of a 79-year-old client with heart failure calls the clinic. The client has followed a 2,000-mg sodium diet for 2 months and now eats only a few bites at each meal. The daughter reports that the client has lost 4 kg (8.8 lb), has stopped attending church, and recently said, "Food has no flavor, and nothing matters anymore." Which action should the nurse take?
Advise the daughter to offer a high-calorie liquid supplement with each meal
Tell the daughter to add a little salt to the client's food so that the meals have more flavor
Request a prescription for an appetite stimulant from the health care provider
Schedule a visit this week to screen the client for depression with a standardized tool
Answer it, then check it.
Answer and rationale
Answer
- D: Schedule a visit this week to screen the client for depression with a standardized tool
The key, and why
Heart failure is a condition in which the heart cannot pump enough blood to meet the body's needs.
Poor appetite and weight loss in an older adult with heart failure are easy to blame on a bland diet, but this client has more than a taste complaint. Withdrawal from church, a valued activity, and the statement that nothing matters anymore are signs of depression. Depression is common in heart failure, it worsens appetite and adherence, and in older adults it carries a real risk of suicide.
The nurse arranges a prompt assessment with a standardized screening tool, such as the Geriatric Depression Scale or the PHQ-9, which includes asking about thoughts of self-harm. Treating depression often restores appetite, and the diet can then be made more appealing with herbs, spices, and the client's preferred foods.
Each distractor
Option A adds calories, which may help later, but it skips the assessment of the problem behind the weight loss.
Option B adds sodium, which leads to fluid retention and readmission in heart failure, and it treats the taste complaint while missing the mood change.
Option C goes straight to a medication for appetite without finding the cause. If the cause is depression, an appetite stimulant does not treat it.
The teaching point
Weight loss + WITHDRAWAL + "nothing matters" in an older adult = SCREEN for DEPRESSION. Assess before treating. Depression worsens APPETITE and ADHERENCE in heart failure. Do NOT add salt to fix bland food. Use HERBS and SPICES.
9Ordered responseNutrition
The nurse is reinforcing the dietitian's teaching with a 64-year-old client with stage 4 chronic kidney disease who wants to continue eating potatoes. The client's serum potassium is 5.3 mEq/L, and the dietitian has taught the client to leach potatoes, a method that lowers the potassium content of the potato before cooking. Place the following steps in the order the client should perform them.
Drag the responses into the order you want. Drag one back to the list to remove it.
Your order
1Drag a response here
2Drag a response here
3Drag a response here
4Drag a response here
5Drag a response here
Responses
Drain the potatoes and discard the water they were boiled in
Peel the potatoes and cut them into thin slices or small cubes
Rinse the cut pieces under warm running water
Boil the pieces in a large pot of unsalted water for about 10 minutes
Finish the potatoes by roasting, frying, or mashing them
Answer it, then check it.
Answer and rationale
Answer
- 1: Peel the potatoes and cut them into thin slices or small cubes
- 2: Rinse the cut pieces under warm running water
- 3: Boil the pieces in a large pot of unsalted water for about 10 minutes
- 4: Drain the potatoes and discard the water they were boiled in
- 5: Finish the potatoes by roasting, frying, or mashing them
The key, and why
Leaching works because potassium dissolves in water. Peeling removes the skin, which holds much of the potassium, and cutting the potato into thin slices or small cubes exposes far more surface for the potassium to move into the water. A rinse washes the potassium off the cut surfaces.
Boiling the pieces in a large volume of water draws more potassium out, and that water is thrown away, because the potassium is now in it. Only then are the potatoes roasted, fried, or mashed. This method lowers the potassium in potatoes by roughly half, which lets the client keep a favorite food in small portions while staying within the limit.
Each distractor
Boiling whole, unpeeled potatoes before cutting them removes very little potassium, because the skin and the small surface area hold it in.
Roasting or frying the potatoes before boiling them skips the step that removes the potassium, and roasting alone removes none.
Keeping the cooking water for gravy or soup puts the potassium straight back into the meal.
The teaching point
To lower POTASSIUM in potatoes and root vegetables = PEEL, CUT SMALL, RINSE, BOIL in plenty of water, DISCARD the water, then FINISH cooking. The potassium goes INTO THE WATER. Never reuse it. Even prepared this way, PORTIONS still count.
10Multiple choice, single answerNutrition
A client's blood glucose has come back up to 88 mg/dL after orange juice. The next meal is three hours away. Which snack should the nurse offer?
A second glass of orange juice
Crackers with peanut butter
A sugar-free gelatin cup
A piece of fruit and a glass of water
Answer it, then check it.
Answer and rationale
Answer
- B: Crackers with peanut butter
The key, and why
Hypoglycemia is a blood glucose below 70 mg/dL. Even after treatment, the glucose can drop again if the cause, usually insulin that is still acting, is still present.
The juice has done its job, but simple sugar is used up quickly. With the next meal 3 hours away, the client needs a snack that combines carbohydrate with protein or a complex starch so the glucose stays up. Crackers with peanut butter is that combination. Half a sandwich or a glass of milk would work the same way.
Each distractor
Option A is a second fast sugar with nothing behind it. The glucose goes up again and comes straight back down.
Option C has no carbohydrate in it at all, so it does nothing to hold the glucose up.
Option D is more fast sugar with some fiber attached. It is a perfectly good snack and it does not hold the glucose up the way a starch with protein does.
The teaching point
Fast sugar treats the low. SUGAR PLUS STARCH OR PROTEIN keeps it up. Crackers and peanut butter. Apple juice and turkey. Half a cup of skim milk. ONE sugar is good. TWO sugars is a WRONG answer. The insulin that caused the low is STILL WORKING.
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