Reviewed September 30, 2026 by the editorial team. Educational content; follow your facility's protocols.
Complete blood count (CBC)
The CBC counts and sizes the cells in the blood. Nurses watch hemoglobin for bleeding and anemia, white cells for infection and neutropenia, and platelets for bleeding risk before procedures and injections.
SI values below are unit conversions of the same ranges.
| Test | Conventional units | SI units |
|---|---|---|
| Hemoglobin (female) | 12-16 g/dL | 120-160 g/L |
| Hemoglobin (male) | 14-18 g/dL | 140-180 g/L |
| Hematocrit (female) | 37%-47% | 0.37-0.47 |
| Hematocrit (male) | 42%-50% | 0.42-0.50 |
| White blood cells (WBC) | 4,000-11,000/µL | 4.0-11.0 × 10⁹/L |
| Red blood cells (RBC) | 4.2-5.9 million/µL | 4.2-5.9 × 10¹²/L |
| Platelets | 150,000-450,000/µL | 150-450 × 10⁹/L |
| Mean corpuscular volume (MCV) | 80-98 fL | 80-98 fL |
Hemoglobin and hematocrit ranges differ by sex, age, altitude and pregnancy. Use the range on the lab report.
Basic and comprehensive metabolic panel (BMP/CMP)
The BMP covers electrolytes, kidney function and glucose. The CMP adds calcium-related and liver tests. For sodium, potassium, chloride and bicarbonate, mEq/L and mmol/L are numerically the same.
| Test | Conventional units | SI units |
|---|---|---|
| Sodium (Na) | 136-145 mEq/L | 136-145 mmol/L |
| Potassium (K) | 3.5-5.0 mEq/L | 3.5-5.0 mmol/L |
| Chloride (Cl) | 98-106 mEq/L | 98-106 mmol/L |
| Bicarbonate (CO2) | 23-28 mEq/L | 23-28 mmol/L |
| Blood urea nitrogen (BUN) | 8-20 mg/dL | 2.9-7.1 mmol/L (urea) |
| Creatinine (female) | 0.50-1.10 mg/dL | 44-97 µmol/L |
| Creatinine (male) | 0.70-1.30 mg/dL | 62-115 µmol/L |
| Glucose, fasting | 70-99 mg/dL | 3.9-5.5 mmol/L |
| Calcium, total | 8.6-10.2 mg/dL | 2.15-2.55 mmol/L |
| Magnesium | 1.6-2.6 mg/dL | 0.66-1.07 mmol/L |
| Phosphorus | 3.0-4.5 mg/dL | 0.97-1.45 mmol/L |
Total calcium falls when albumin is low. Check the albumin before you report a low calcium, and follow your facility's approach to correction or ionized calcium.
Liver panel
Liver tests show cell injury (ALT, AST), bile flow (alkaline phosphatase, bilirubin) and synthetic function (albumin, total protein). Albumin also matters for nutrition, wound healing and fluid balance.
| Test | Conventional units | SI units |
|---|---|---|
| Albumin | 3.5-5.5 g/dL | 35-55 g/L |
| Total protein | 5.5-9.0 g/dL | 55-90 g/L |
| ALT (SGPT) | 10-40 U/L | 10-40 U/L |
| AST (SGOT) | 10-40 U/L | 10-40 U/L |
| Alkaline phosphatase (ALP) | 30-120 U/L | 30-120 U/L |
| Bilirubin, total | 0.3-1.0 mg/dL | 5.1-17.1 µmol/L |
| Bilirubin, direct | 0.1-0.3 mg/dL | 1.7-5.1 µmol/L |
Enzyme ranges (ALT, AST, ALP) depend heavily on the analyzer and method. Always compare with the lab's own range.
Coagulation: PT, INR and aPTT
Coagulation tests tell you how long blood takes to clot. The PT and INR track the extrinsic pathway and warfarin therapy. The aPTT tracks the intrinsic pathway and unfractionated heparin therapy.
| Test | Reference range | Note |
|---|---|---|
| Prothrombin time (PT) | 11-13 seconds | StatPearls cites 10-13 seconds; varies with the reagent |
| INR | 1.1 or below | Healthy person not on anticoagulants |
| INR on warfarin | 2-3 for most patients | Target is set by the prescriber for each patient |
| Activated partial thromboplastin time (aPTT) | 25-35 seconds | Heparin targets follow facility protocol |
| Fibrinogen | 200-400 mg/dL | 2.0-4.0 g/L |
A therapeutic INR or aPTT on anticoagulation is expected to sit above the normal range. Compare the result with the patient's ordered target, not with the healthy range.
Arterial blood gases (ABGs)
ABGs show acid-base balance and oxygenation. ABIM lists narrow ranges; most nursing courses teach the wider ranges from StatPearls. Both are shown so you can match your textbook or exam.
| Value | ABIM range | Range commonly taught (StatPearls) |
|---|---|---|
| pH | 7.38-7.44 | 7.35-7.45 |
| PaCO2 | 38-42 mm Hg | 35-45 mm Hg |
| PaO2 | 75-100 mm Hg | 75-100 mm Hg |
| HCO3 | 23-26 mEq/L | 22-26 mEq/L |
| SaO2 | 95% or higher | 95%-100% |
| Base excess | Not listed | -4 to +2 |
PaO2 normally falls with age and depends on the oxygen the patient is breathing. Interpret it with the FiO2 at the time of the draw.
Glucose, A1C and lipid panel
Glucose and A1C screen for and monitor diabetes. The CDC uses the thresholds below. Lipid categories come from the ABIM table; treatment goals are set by the provider based on overall cardiovascular risk.
| Test | Normal or desirable | Abnormal categories |
|---|---|---|
| Fasting plasma glucose | 99 mg/dL or below | Prediabetes 100-125 mg/dL; diabetes 126 mg/dL or above |
| Hemoglobin A1C | Below 5.7% | Prediabetes 5.7%-6.4%; diabetes 6.5% or above |
| 2-hour glucose tolerance test | Below 140 mg/dL | Prediabetes 140-199 mg/dL; diabetes 200 mg/dL or above |
| Total cholesterol | Below 200 mg/dL | Borderline-high 200-239; high 240 or above |
| LDL cholesterol | Below 100 mg/dL (optimal) | Near-optimal 100-129; borderline-high 130-159; high 160-189; very high 190 or above |
| HDL cholesterol | 40 mg/dL or above (men); 50 or above (women) | Low below 40 (men) or below 50 (women) |
| Triglycerides (fasting) | Below 150 mg/dL (below 100 optimal) | Borderline-high 150-199; high 200-499; very high 500 or above |
A diabetes diagnosis needs a confirmed result, usually a repeat test. A single value on a lab sheet is not a diagnosis.
Cardiac markers and lactate
Troponin rises when heart muscle is injured. There is no single normal troponin value: each assay has its own 99th percentile upper reference limit, and high-sensitivity assays report in ng/L instead of ng/mL. Read the cut-off printed by your lab, and watch the trend between serial draws.
BNP helps assess heart failure. Lactate rises with poor tissue perfusion and is part of sepsis screening.
| Test | Reference range | Note |
|---|---|---|
| Troponin I (conventional assay) | 0.04 ng/mL or below (ABIM example) | Assay-specific; use the lab's 99th percentile cut-off |
| Troponin T (conventional assay) | 0.01 ng/mL or below (ABIM example) | High-sensitivity assays report in ng/L with their own cut-offs |
| B-type natriuretic peptide (BNP) | Below 100 pg/mL | NT-proBNP uses different cut-offs |
| Lactate | 0.7-2.1 mmol/L | Rises in shock and sepsis |
Urinalysis basics
A urinalysis has three parts: a visual check (color and clarity), a dipstick (chemical tests) and a microscopic exam. Collect a clean-catch midstream sample and send it promptly, because standing urine changes its pH and cell counts.
| Finding | Typical normal result |
|---|---|
| Color and clarity | Pale yellow to amber; clear |
| Specific gravity | 1.002-1.030 (ABIM); usually 1.016-1.022 |
| pH | 4.5-8.0; usually 5.5-6.5 |
| Protein, glucose, ketones | Negative |
| Blood | Negative |
| Nitrite and leukocyte esterase | Negative |
| Bilirubin | Negative |
| Urobilinogen | 0.1-1 mg/dL |
| Red blood cells | 0-5 per high-power field |
| White blood cells | 0-5 per high-power field |
| Casts | Occasional hyaline casts only |
Nursing priorities and critical values
A critical (panic) value is a result that may mean immediate danger and must be reported to the responsible provider without delay. Each laboratory sets its own list, so the thresholds differ between facilities. The examples below come from two published US lab lists and show how much they vary. They are not universal cut-offs.
When you receive a critical result: verify the patient identifiers, read the value back to the caller, assess the patient, notify the provider within your facility's time frame and document who you told, when, and what was ordered.
| Test | Example: Labcorp (2024) | Example: Brown University Health |
|---|---|---|
| Potassium | Below 2.5 or above 6.5 mmol/L | Below 3.0 or above 6.0 mEq/L |
| Sodium | Below 120 or above 160 mmol/L | Below 125 or above 150 mEq/L |
| Glucose | Below 40 or above 500 mg/dL | Below 55 or above 400 mg/dL |
| Calcium, total | Below 7.0 or above 13.0 mg/dL | Below 7 or above 11.5 mg/dL |
| Hemoglobin | Below 6.1 or above 21.4 g/dL | Below 7.0 g/dL |
| Platelets | Below 21 × 10³/µL | Below 20,000 or above 1,000,000/µL |
| INR | Above 4.9 | Above 5 |
| aPTT | Above 89 seconds | Above 135 seconds |
These are examples only and vary by facility. Always use your own laboratory's critical value list and escalation policy.
Frequently asked questions
What are the most important normal lab values for nurses to know?
Start with sodium (136-145 mEq/L), potassium (3.5-5.0 mEq/L), fasting glucose (70-99 mg/dL), hemoglobin (12-16 g/dL in women, 14-18 g/dL in men), WBC (4,000-11,000/µL), platelets (150,000-450,000/µL), creatinine, INR and the ABG values. These drive most bedside decisions.
Why do normal lab values differ between books and labs?
Each laboratory sets its reference range from its own analyzers, reagents and population. Textbooks round or widen ranges for teaching. The range printed on the patient's report is the one that applies.
What is a normal INR?
About 1.1 or below in a person who is not taking an anticoagulant. For most patients on warfarin the therapeutic target is 2 to 3, but the prescriber sets the target for each patient.
What are normal ABG values?
Most nursing references use pH 7.35-7.45, PaCO2 35-45 mm Hg, HCO3 22-26 mEq/L, PaO2 75-100 mm Hg and SaO2 95%-100%. ABIM lists narrower ranges, for example pH 7.38-7.44.
What is a normal troponin level?
There is no single number. Each troponin assay has its own upper reference limit, set at the 99th percentile of a healthy population, and high-sensitivity assays report in ng/L. Use the cut-off printed by your lab and compare serial results.
What is the difference between an abnormal and a critical lab value?
An abnormal value falls outside the reference range. A critical value is far enough outside it to suggest immediate risk, and your facility requires you to report it to the provider right away. Each lab publishes its own critical list.
More guides and tools
All scales:
Sources: ABIM Laboratory Test Reference Ranges, January 2026 · Normal Laboratory Values - Merck Manual Professional Version · Prothrombin Time - StatPearls, NCBI Bookshelf · Arterial Blood Gas - StatPearls, NCBI Bookshelf · Diabetes Testing - CDC. Text written by our editorial team. Reviewed September 30, 2026.