The NCLEX-RN does not ask you to recite lab ranges in isolation. It gives you a value, a client, and a set of actions, and asks what matters and what to do. This guide groups the values nurses use every day, explains the signs of each imbalance, and links every abnormal result to a nursing action. Reference ranges vary slightly between laboratories; the numbers here are commonly taught adult values.
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Progress Note Editorial
Evidence-based · For exam prep, not medical advice
update Updated October 2026
Date of last content change
Built by surgery and anesthesiology residents
Written for the NCLEX-RN · Free to read
bolt The 60-second version
The NCLEX-RN does not ask you to recite lab ranges in isolation. It gives you a value, a client, and a set of actions, and asks what matters and what to do.
check_circleElectrolytes: sodium 135–145 mEq/L; potassium 3.5–5.0 mEq/L; total calcium about 8.5–10.5 mg/dL; magnesium about 1.5–2.5 mg/dL (ranges vary by lab).
check_circlePotassium is the most dangerous electrolyte to get wrong: both low and high levels cause dysrhythmias. IV potassium is never given by IV push.
check_circleCBC: WBC about 5,000–10,000/mm³; hemoglobin about 12–16 g/dL (female) and 14–18 g/dL (male); platelets 150,000–400,000/mm³.
check_circleCoagulation: INR about 1.0 off warfarin (target usually 2–3 on warfarin); aPTT about 30–40 seconds (therapeutic heparin about 1.5–2.5 times control).
check_circleABGs: pH 7.35–7.45; PaCO₂ 35–45 mm Hg; HCO₃⁻ 22–26 mEq/L; PaO₂ 80–100 mm Hg.
check_circleAlways compare a value with the client's baseline and trend, assess the client, and follow facility critical-value policy for reporting.
target What you'll be able to do · aligned to NCLEX-RN Test Plan · Reduction of Risk Potential
RISK REDIdentify normal ranges and the clinical significance of common adult lab values.
PHYS ADAPTRecognize the signs of sodium, potassium, calcium, and magnesium imbalances.
RISK REDInterpret arterial blood gases using a stepwise method.
PHARMUse drug levels and coagulation tests to give medications safely.
How lab values are tested on the NCLEX-RN
Lab items fall mainly under Reduction of Risk Potential (12% of the 2026 test plan) and Pharmacological Therapies. The question is almost always "which result needs follow-up?" or "what should the nurse do first?"
workspace_premium Value + client + action
A potassium of 3.3 mEq/L matters much more in a client taking digoxin. A platelet count of 90,000/mm³ matters much more in a client on heparin. Read every lab in the context of the client's drugs and condition, then choose the action.
Abnormal lab workflow. A critical value is reported to the provider promptly, and the report is documented, per facility policy.
Electrolytes
Electrolyte imbalances produce predictable neuromuscular and cardiac signs.
Electrolyte
Usual adult range
Low: key signs
High: key signs
Sodium
135–145 mEq/L
Confusion, headache, seizures; correct slowly
Thirst, agitation, dry mucosa; seizures if severe
Potassium
3.5–5.0 mEq/L
Muscle weakness, cramps, constipation, flat T waves, U waves
Muscle weakness, peaked T waves, dysrhythmias
Calcium (total)
About 8.5–10.5 mg/dL
Tetany, Trousseau and Chvostek signs, prolonged QT
Weakness, constipation, kidney stones, confusion
Magnesium
About 1.5–2.5 mg/dL
Tremor, hyperreflexia, torsades; makes hypokalemia hard to correct
Loss of deep tendon reflexes, respiratory depression, hypotension
Phosphorus
About 2.5–4.5 mg/dL
Weakness (refeeding syndrome)
Usually with kidney failure; itching, low calcium
Ranges vary by laboratory and units; use the reference range on the client's report.
Potassium safety. IV potassium is always diluted and given on a pump, never as an IV push; peripheral rates are limited by policy.
Blood counts and coagulation
Counts and clotting tests guide infection precautions, bleeding precautions, and anticoagulant doses.
Critical-value thresholds are set by each facility.
NGN-style case
Prioritizing among several abnormal values is a frequent item type.
functions Clinical judgment case — which value first?
The nurse reviews morning labs. Which result requires the most immediate action? (A) Hemoglobin 11.8 g/dL in a client after surgery; (B) potassium 6.4 mEq/L in a client with kidney failure; (C) glucose 182 mg/dL in a client on prednisone; (D) INR 2.6 in a client on warfarin for atrial fibrillation.
Recognize cues: potassium 6.4 mEq/L is well above 5.0.
Analyze: hyperkalemia can cause fatal dysrhythmias.
The other results are mildly abnormal or within the expected target (INR 2.6 is therapeutic).
Act: assess the client, place on a cardiac monitor, and notify the provider; anticipate treatment to stabilize the heart and lower potassium.
Answer. Client B. Hyperkalemia is the greatest immediate threat to life.
Straight from the Progress Note question bank, each with a cited explanation. No account needed.
123
A client is NPO before surgery but takes an essential daily antiseizure medication. Which action by the nurse is most appropriate?
Answer: C. Some essential medications, such as antiseizure drugs, may be continued with a small sip of water even when a client is NPO, so the nurse clarifies the plan with the provider (option C). Holding all medications because the client is NPO (A) could stop a critical drug and precipitate seizures. Giving all usual medications with a full glass of water (B) violates the NPO status and increases aspiration risk. Giving the antiseizure medication only if the client requests it (D) leaves a critical decision to chance. Clarifying which essential medications may be given safely balances the NPO requirement with the client's needs. The nurse follows the provider's instructions and documents the plan.
A minor child who is a client requires emergency treatment, and the parents cannot be reached for consent. Which action by the nurse is most appropriate?
Answer: B. In a true emergency when a parent cannot be reached, care needed to prevent serious harm proceeds under emergency (implied) consent, so the nurse supports providing the treatment (option B). Delaying all treatment until a parent is reached (A) risks serious harm to the child. Having the minor sign the consent (C) is not valid, since a minor generally cannot give consent. Canceling the treatment (D) withholds emergency care the child needs. Recognizing the emergency-consent doctrine allows life- or limb-saving care without delay. The team continues efforts to reach the parents and documents the emergency and the care given.
A client whose spouse died in a motor vehicle crash the client was driving says, “It is my fault; I should have protected them.” Which response by the nurse is most therapeutic?
Answer: C. Acknowledging the client's feelings and gently encouraging them to talk invites the client to express guilt and grief, which is the therapeutic response (option C). Telling the client it was clearly not their fault (A) dismisses the feeling and can end the conversation. Changing the subject (B) avoids the emotion the client is expressing. Reassuring the client they will feel better with time (D) minimizes present distress and offers little support. Presence and open exploration help the grieving, guilt-laden client feel heard. The nurse assesses coping and support and involves resources as appropriate.
Which lab values should I memorize for the NCLEX?expand_more
Sodium, potassium, calcium, magnesium, glucose, BUN, creatinine, CBC (WBC, hemoglobin, hematocrit, platelets), PT/INR, aPTT, ABGs, and the common drug levels (digoxin, lithium, phenytoin).
What is the normal potassium range?expand_more
About 3.5 to 5.0 mEq/L. Both low and high potassium can cause dangerous dysrhythmias.
How do I interpret an ABG quickly?expand_more
Check the pH, then see whether PaCO₂ (respiratory) or HCO₃⁻ (metabolic) explains it. In respiratory problems PaCO₂ moves opposite to pH; in metabolic problems HCO₃⁻ moves in the same direction.
Can IV potassium be pushed?expand_more
Never. IV potassium is always diluted and given by infusion pump at a rate limited by facility policy, because a bolus can cause cardiac arrest.