Lab Values Nursing Cheat Sheet — Normal Ranges
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Your patient's potassium just came back at 2.8.
Do you know if that's dangerous? Do you know what to watch for? Do you know what to do next?
Lab values are one of those things nursing school throws at you expecting you to just absorb them. No system. No logic. Just memorize 300 numbers and hope for the best.
This post gives you a system. The values that actually show up on NCLEX and in clinical — organized, explained, and paired with what each abnormal result means for your patient.
How to Read a Lab Value
Every lab result has three zones:
- Normal range — where healthy patients fall
- Abnormal — outside normal, needs monitoring
- Critical value — requires immediate intervention
On NCLEX, critical values always require you to act first — before documenting, before notifying the charge nurse, before anything else.
Complete Blood Count (CBC)
| Lab Value | Normal Range | Low Means | High Means |
|---|---|---|---|
| WBC | 4,500–11,000/µL | Infection risk, immunosuppression | Infection, leukemia |
| RBC (male) | 4.5–5.5 million/µL | Anemia | Polycythemia |
| RBC (female) | 4.0–5.0 million/µL | Anemia | Polycythemia |
| Hemoglobin (male) | 13.5–17.5 g/dL | Anemia, bleeding | Dehydration, COPD |
| Hemoglobin (female) | 12.0–15.5 g/dL | Anemia, bleeding | Dehydration, COPD |
| Hematocrit (male) | 41–53% | Anemia, overhydration | Dehydration, burns |
| Hematocrit (female) | 36–46% | Anemia, overhydration | Dehydration, burns |
| Platelets | 150,000–400,000/µL | Bleeding risk | Clotting risk |
Critical values to know: WBC below 2,000 (neutropenia — reverse isolation). Platelets below 50,000 (bleeding precautions). Hemoglobin below 7 (transfusion likely).
Basic Metabolic Panel (BMP)
| Lab Value | Normal Range | Low Means | High Means |
|---|---|---|---|
| Sodium (Na+) | 136–145 mEq/L | Hyponatremia — confusion, seizures | Hypernatremia — thirst, dry mucous membranes |
| Potassium (K+) | 3.5–5.0 mEq/L | Hypokalemia — muscle weakness, dysrhythmias | Hyperkalemia — peaked T waves, cardiac arrest |
| Chloride (Cl-) | 98–106 mEq/L | Metabolic alkalosis, vomiting | Metabolic acidosis, dehydration |
| CO2/Bicarb (HCO3-) | 22–29 mEq/L | Metabolic acidosis | Metabolic alkalosis |
| BUN | 10–20 mg/dL | Malnutrition, liver failure | Dehydration, kidney disease |
| Creatinine | 0.6–1.2 mg/dL | Low muscle mass | Kidney dysfunction — most specific renal marker |
| Glucose (fasting) | 70–100 mg/dL | Hypoglycemia — shaky, diaphoretic | Hyperglycemia — polyuria, polydipsia |
| Calcium (Ca2+) | 8.5–10.5 mg/dL | Hypocalcemia — Trousseau's, Chvostek's signs | Hypercalcemia — bones, groans, stones, moans |
The two you MUST know cold: Potassium and Glucose. These appear on almost every NCLEX pharmacology and med-surg question.
Cardiac Markers
| Lab Value | Normal | Elevated Means |
|---|---|---|
| Troponin I | <0.04 ng/mL | Myocardial damage — most specific for MI |
| Troponin T | <0.01 ng/mL | Myocardial damage — rises 3–4 hrs after MI |
| CK-MB | <5% of total CK | Heart muscle damage |
| BNP | <100 pg/mL | Heart failure — the higher, the worse |
NCLEX tip: Troponin is the gold standard for diagnosing MI. If a question asks which lab confirms a heart attack — always Troponin.
Coagulation Studies
| Lab Value | Normal Range | Used For |
|---|---|---|
| PT (Prothrombin Time) | 11–13.5 seconds | Monitors Warfarin therapy |
| INR | 0.8–1.1 (therapeutic 2–3) | Monitors Warfarin — target 2–3 for most patients |
| aPTT | 25–35 seconds | Monitors Heparin therapy |
| Therapeutic aPTT | 46–70 seconds | Heparin is working when 1.5–2× normal |
Memory trick: Warfarin → PT/INR (W comes before H, P comes before A). Heparin → aPTT.
Liver Function Tests (LFTs)
| Lab Value | Normal Range | Elevated Means |
|---|---|---|
| ALT | 7–56 units/L | Liver cell damage — most specific for liver |
| AST | 10–40 units/L | Liver or muscle damage |
| Total Bilirubin | 0.1–1.2 mg/dL | Jaundice, liver disease, hemolysis |
| Albumin | 3.5–5.0 g/dL | Low = malnutrition, chronic liver disease |
The One Rule That Saves You on NCLEX
When a lab value is critical — the answer is always notify the provider first, then intervene.
When a lab value is abnormal but not critical — assess the patient first, then notify.
This single rule answers more NCLEX questions than any other concept in lab values.
Want All Lab Values in One Place?
Our Lab Values Nursing Study Guide puts every reference value you need into 16 clean, printable pages:
- Complete CBC, BMP, LFT, and coagulation reference tables
- Critical values with immediate nursing actions
- Arterial Blood Gas interpretation step-by-step
- Urinalysis, thyroid, and specialty lab values
- Quick reference cheat sheet + 10 NCLEX practice questions with rationales
16 pages. Instant PDF download. $5.99.