Lab values for the NCLEX-RN: the normal ranges, and why sources disagree about them
The 2026 test plan asks you to compare a client's results with normal values, and it does not say whether the exam shows reference ranges. Learn the common adult ranges, but expect small differences between sources: even NIH's MedlinePlus gives different sodium and calcium ranges on different pages.
Published September 19, 2026
Lab values are tested under Reduction of Risk Potential, 9 to 15% of the NCLEX-RN under the 2026 test plan. Its content area on laboratory values asks you to compare client laboratory values to normal laboratory values, monitor results such as glucose for a client with diabetes, and notify the provider about results. We searched the full test plan and it does not say whether exam questions include reference ranges, so it is safest to assume some won't.
There is no single official list of normal values. Every lab sets its own ranges, and NIH's MedlinePlus says so on each of its test pages: normal value ranges may vary slightly among different labs. What matters on the exam is recognizing a value that is clearly abnormal and knowing what it means for the client, far more than defending the last decimal of a range.
Chemistry
These are adult ranges from MedlinePlus's comprehensive metabolic panel page, with differences from other sources noted beside them.
| Test | MedlinePlus range | Where sources differ |
|---|---|---|
| Sodium | 135 to 145 mEq/L | MedlinePlus's basic panel page gives 136 to 144 |
| Potassium | 3.7 to 5.2 mEq/L | Most nursing textbooks teach 3.5 to 5.0; NIH's StatPearls puts the lower limit at 3.5 |
| Calcium, total | 8.5 to 10.2 mg/dL | Another MedlinePlus page gives 8.8 to 10.3 |
| Magnesium | 1.7 to 2.2 mg/dL | StatPearls gives 1.46 to 2.68 |
| Chloride | 96 to 106 mEq/L | Another MedlinePlus page gives 98 to 107 |
| Bicarbonate (CO2) | 23 to 29 mEq/L | |
| BUN | 6 to 20 mg/dL | |
| Creatinine | 0.6 to 1.3 mg/dL | MedlinePlus's basic panel page gives 0.8 to 1.2 |
| Glucose | 70 to 100 mg/dL | MedlinePlus's basic panel page gives 64 to 100 |
Blood counts and clotting
| Test | Range | Source |
|---|---|---|
| Hemoglobin | Male 13.8 to 17.2 g/dL; female 12.1 to 15.1 g/dL | MedlinePlus hemoglobin page |
| Hematocrit | Male 37 to 48%; female 34 to 43% | MedlinePlus hematocrit page |
| White blood cells | 4,500 to 11,000 per microliter | MedlinePlus |
| Platelets | 150,000 to 400,000 per microliter | MedlinePlus |
| INR, not on warfarin | 0.8 to 1.1 | MedlinePlus |
| INR, on warfarin | Usually kept at 2.0 to 3.0 | MedlinePlus |
MedlinePlus's complete blood count page gives wider hemoglobin and hematocrit ranges than its single-test pages do, which is another reason to learn roughly where normal sits instead of memorizing one source's figures. The INR target on warfarin is the one most likely to appear as a judgment question, because a result above it raises the bleeding risk.
Arterial blood gases
MedlinePlus lists pH 7.38 to 7.42, PaCO2 38 to 42 mm Hg, HCO3 22 to 28 and PaO2 75 to 100 mm Hg. Nursing programs usually teach a wider pH range of 7.35 to 7.45 and PaCO2 of 35 to 45, and those are the figures most candidates use to interpret a blood gas. Interpretation turns on direction more than exact limits: whether the pH is acidic or alkaline, and whether the carbon dioxide or the bicarbonate explains it.
Glucose and A1C thresholds
The Centers for Disease Control and Prevention sets the diagnostic cutoffs. A fasting glucose of 99 mg/dL or below is normal, 100 to 125 indicates prediabetes, and 126 or above indicates diabetes. An A1C below 5.7% is normal, 5.7 to 6.4% indicates prediabetes, and 6.5% or above indicates diabetes.
What to do with a range
Most lab questions ask what the value means for the client in front of you. A potassium of 5.8 mEq/L matters more for a client with kidney failure starting a potassium-sparing drug than as a number on its own. The electrolytes are covered in more depth, including their signs, in fluids and electrolytes on the NCLEX.
Our NCLEX practice questions give lab values inside client records the way case studies do, so you practice reading them in context. NCLEX case studies explained shows how the record is used across a case.
Related
- Fluids and electrolytes on the NCLEX: potassium, sodium, calcium and magnesium, and the signs that matter
- NCLEX case studies explained: one client, six questions, six steps of clinical judgment
Our NCLEX-RN practice is built on the April 2026 test plan, with unfolding case studies and every Next Gen question type. Sit a full adaptive exam free, with no email or card.
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