Adult reference ranges with a plain-language line on what a high or a low commonly signals. Sourced, printable, and your facility's ranges win.
Reference ranges: Open RN, Health Alterations, Appendix A — CC BY 4.0. Retrieved 2026-08-14.
| Test | Typical adult range | High commonly signals | Low commonly signals |
|---|---|---|---|
| RBC (red blood cell count) | M 4.50 – 5.90 million/mm3F 4.00 – 5.20 million/mm3 | dehydration, chronic low oxygen, polycythemia | blood loss, anemia, bone marrow suppression |
| RDW (red cell distribution width) | 11.5% – 14.5% | red cells of mixed sizes, often an early or combined nutritional anemia | rarely meaningful on its own |
| MCV (mean corpuscular volume) | 80 – 100 fL | B12 or folate deficiency, alcohol use, some marrow disorders | iron deficiency, thalassemia trait, chronic disease |
| MCH (mean corpuscular hemoglobin) | 0.4 – 0.5 fmol/cell | tracks with large-cell (macrocytic) anemia | tracks with iron deficiency and small-cell anemia |
| MCHC (mean corpuscular hemoglobin concentration) | 30 – 35 g/dL | hereditary spherocytosis, or a sample handling artifact | iron deficiency, chronic blood loss |
| Hemoglobin | M 13 – 17 g/dLF 12 – 15 g/dL | dehydration, chronic low oxygen, smoking | bleeding, anemia, fluid overload diluting the sample |
| Hematocrit | M 40% – 52%F 36% – 47% | dehydration, polycythemia | bleeding, anemia, overhydration |
| WBC (white blood cells) | 4,000 – 10,000 mm3 | infection, inflammation, stress response, steroid effect | marrow suppression, overwhelming infection, some viral illness |
| Neutrophils | 46 – 78% | bacterial infection, acute inflammation, tissue injury | neutropenia, and with it a higher infection risk |
| Lymphocytes | 18 – 52% | viral infection, some chronic infections and leukemias | acute stress, steroid effect, HIV, immunosuppression |
| Monocytes | 3 – 10% | chronic infection, the recovery phase of inflammation | marrow suppression |
| Eosinophils | 0 – 6% | allergy, asthma, parasitic infection, drug reaction | acute stress response, steroid effect |
| Basophils | 0 – 3% | allergic reaction, some myeloproliferative disorders | rarely meaningful on its own |
| Platelet count | 150,000 – 400,000 mm3 | inflammation, iron deficiency, absent spleen; clot risk when very high | bleeding and bruising risk, marrow suppression, platelet consumption |
| Test | Typical adult range | High commonly signals | Low commonly signals |
|---|---|---|---|
| Sodium | 135 – 145 mmol/L | water deficit, dehydration, high salt load; confusion at extremes | fluid overload, SIADH, diuretic effect; confusion and seizure risk when very low |
| Potassium | 3.5 – 5 mmol/L | kidney impairment, acidosis, cell breakdown; heart rhythm risk | GI losses, diuretic effect, alkalosis; weakness and heart rhythm risk |
| Chloride | 95 – 105 mmol/L | dehydration, metabolic acidosis, excess saline | vomiting, gastric suction, metabolic alkalosis |
| Calcium | 8.5 – 10.2 mg/dL | overactive parathyroid, malignancy, prolonged immobility | kidney disease, low albumin, thyroid or parathyroid surgery; muscle spasm and tingling |
| Magnesium | 1.5 – 2 mEq/L | kidney impairment, excess supplementation; slowed reflexes | alcohol use, GI losses, diuretic effect; tremor and heart rhythm risk |
| Phosphate | 0.8 – 1.5 mmol/L | kidney impairment, cell breakdown | malnutrition, refeeding after starvation, heavy antacid use |
| Glucose | 65 – 110 mg/dL | diabetes, stress response, infection, steroid effect | fasting, too much insulin effect, liver failure, alcohol use |
| BUN (blood urea nitrogen) | 8 – 21 mg/dL | dehydration, kidney impairment, GI bleeding, high protein load | overhydration, liver disease, low protein intake |
| Creatinine | 0.8 – 1.3 mg/dL | kidney impairment, dehydration, large muscle mass | low muscle mass, pregnancy |
| Test | Typical adult range | High commonly signals | Low commonly signals |
|---|---|---|---|
| ALP (alkaline phosphatase) | 50 – 100 U/L | bile duct obstruction, bone turnover, pregnancy | malnutrition, low zinc; uncommon |
| ALT (alanine aminotransferase) | 5 – 30 U/L | liver cell injury; the more liver-specific of the two transaminases | rarely meaningful on its own |
| AST (aspartate aminotransferase) | 5 – 30 U/L | liver injury, and also muscle or heart injury | rarely meaningful on its own |
| Albumin | 35 – 50 g/L | dehydration concentrating the sample | malnutrition, liver disease, protein loss, chronic inflammation; swelling |
| Total protein | 60 – 80 g/L | dehydration, chronic inflammation, some blood cancers | malnutrition, liver disease, protein-losing kidney or gut conditions |
| Total bilirubin | 2 – 20 µmol/L | red cell breakdown, liver disease, bile obstruction; jaundice | rarely meaningful on its own |
| Amylase | 30 – 125 U/L | pancreatitis, salivary gland disorders, bowel obstruction | advanced chronic pancreatitis, severe liver disease |
| Test | Typical adult range | High commonly signals | Low commonly signals |
|---|---|---|---|
| Prothrombin time (PT) | 11 – 14 sec | anticoagulant effect, liver disease, vitamin K deficiency; bleeding risk | rarely meaningful; often a sample handling artifact |
| INR (international normalized ratio) | 0.9 – 1.2 | anticoagulant effect, liver disease; bleeding risk | in someone being anticoagulated, under-treatment and clot risk |
| aPTT (activated partial thromboplastin time) | 20 – 40 sec | anticoagulant effect, clotting factor deficiency; bleeding risk | acute-phase reaction, early consumptive clotting |
| Test | Typical adult range | High commonly signals | Low commonly signals |
|---|---|---|---|
| pH | 7.35 – 7.45 | alkalosis, respiratory or metabolic in origin | acidosis, respiratory or metabolic in origin |
| PaCO2 | 35 – 45 mmHg | under-breathing and CO2 retention; respiratory acidosis | over-breathing from anxiety, pain, or fever; respiratory alkalosis |
| HCO3− | 18 – 22 mmol/L | metabolic alkalosis from vomiting or gastric loss, or compensation for chronic CO2 retention | metabolic acidosis from ketoacidosis, diarrhea, or kidney impairment |
| PaO2 | 80 – 100 mmHg | supplemental oxygen, over-breathing | low blood oxygen from poor gas exchange or mismatched ventilation and perfusion |
Transcribed exactly as printed in the source. Bicarbonate is one of the ranges that differs most between labs, and many report 22 to 26 mmol/L instead. Use the range on your own report.
| Test | Typical adult range | High commonly signals | Low commonly signals |
|---|---|---|---|
| CK (creatine kinase) | 25 – 200 U/L | muscle injury, hard exercise, muscle inflammation, crush injury | low muscle mass; not usually followed |
| CK-MB | 0 – 4 ng/mL | heart muscle injury, and it rises and falls faster than troponin | the expected result |
| Troponin | 0 – 0.4 ng/mL | heart muscle injury; also kidney failure, sepsis, and pulmonary embolism | the expected result |
| Test | Typical adult range | High commonly signals | Low commonly signals |
|---|---|---|---|
| Total cholesterol | 3 – 5.5 mmol/L or < 200 mg/dL | raised cardiovascular risk over time | malnutrition, overactive thyroid, liver disease |
| HDL | 40 – 80 mg/dL | generally a favorable cardiovascular profile | raised cardiovascular risk; often tracks with inactivity and metabolic syndrome |
| LDL | 85 – 125 mg/dL | raised cardiovascular risk and arterial plaque deposition | generally favorable; very low values track with malnutrition or liver disease |
| Triglycerides | 50 – 150 mg/dL | metabolic syndrome, poorly controlled diabetes, alcohol use; pancreatitis risk when very high | malnutrition, overactive thyroid |
| Test | Typical adult range | High commonly signals | Low commonly signals |
|---|---|---|---|
| TSH (thyroid stimulating hormone) | 0.5 – 5 mIU/L | an underactive thyroid, because the body is pushing the gland harder | an overactive thyroid, or a pituitary problem |
| Total thyroxine (T4) | 4.9 – 11.7 mg/dL | overactive thyroid; heat intolerance, weight loss, fast heart rate | underactive thyroid; cold intolerance, fatigue, weight gain |
| Total triiodothyronine (T3) | 0.7 – 1.5 ng/dL | overactive thyroid | underactive thyroid, or severe illness unrelated to the thyroid |
Total T4 is printed as mg/dL in the source and transcribed here unchanged. Most US labs report total T4 in µg/dL over the same numeric span.
| Test | Typical adult range | High commonly signals | Low commonly signals |
|---|---|---|---|
| Total serum iron | M 65 – 180 µg/dLF 30 – 170 µg/dL | iron overload, red cell breakdown, heavy supplementation | iron deficiency, chronic blood loss, poor absorption |
| Ferritin | M 12 – 300 ng/mLF 12 – 150 ng/mL | iron overload, but it also rises with any inflammation, so a normal value can hide a deficiency | iron deficiency; the most specific single marker for it |
| Transferrin | 200 – 350 mg/dL | iron deficiency, as the body makes more carriers to hunt for iron | chronic disease, malnutrition, liver disease |
| Total iron-binding capacity (TIBC) | 45 – 85 µmol/L | iron deficiency | chronic disease, iron overload, malnutrition |
| Test | Typical adult range | High commonly signals | Low commonly signals |
|---|---|---|---|
| A1C | 3.9 – 6.2% | average blood glucose has run high for roughly the past three months | repeated low glucose, or a shortened red cell lifespan that makes the result read low |
| Test | Typical adult range | High commonly signals | Low commonly signals |
|---|---|---|---|
| BNP (brain natriuretic peptide) | < 100 pg/mL | heart failure and fluid overload stretching the ventricle | heart failure is a less likely cause of the breathlessness |
| CRP (C-reactive protein) | < 5 mg/L | inflammation or infection somewhere; it does not say where | no measurable inflammation at the moment |
| D-dimer | < 500 ng/mL | clot formation and breakdown somewhere; also rises with surgery, pregnancy, age, and infection | clot is much less likely; the test earns its keep by ruling out, not ruling in |
| LDH (lactate dehydrogenase) | 50 – 150 U/L | cell or tissue breakdown anywhere in the body; nonspecific | rarely meaningful on its own |
Most of this panel is qualitative, so there is no high and low. The third column is what an abnormal finding commonly signals.
| Test | Typical adult finding | An abnormal result commonly signals |
|---|---|---|
| Appearance | clear | cloudy urine commonly signals infection, crystals, or mucus |
| Color | amber yellow | dark commonly signals concentration or dehydration; red or brown, blood or muscle breakdown |
| Odor | aromatic | strong or foul commonly signals infection; sweet or fruity, ketones |
| pH | 5 – 8 | high commonly signals infection with urea-splitting bacteria; low, metabolic acidosis or a high protein diet |
| Protein | negative | positive commonly signals kidney disease, and can be transient with fever or hard exercise |
| Specific gravity | 1.002 – 1.030 | high commonly signals dehydration; low, overhydration or reduced concentrating ability |
| Leukocyte esterase | negative | positive commonly signals white cells in the urine, usually infection |
| Nitrites | negative | positive commonly signals certain bacteria, and supports a urinary tract infection |
| Ketones | negative | positive commonly signals fasting, a very low carbohydrate intake, or uncontrolled diabetes |
| Bilirubin | negative | positive commonly signals liver or bile duct disease |
| Crystals | negative | present commonly signals a stone-forming tendency, or a sample that sat too long before testing |
| Casts | 0 – 4 hyaline casts/lpf | cellular or increased casts commonly signal kidney involvement rather than a bladder problem |
| Glucose | negative | positive commonly signals blood glucose above the level the kidney can reabsorb |
| WBCs | 0 – 5/hpf | increased commonly signals infection or inflammation in the urinary tract |
| RBCs | 0 – 5/hpf | increased commonly signals infection, stones, trauma, or kidney disease |
This is a study sheet. It is aimed at nursing school, NCLEX prep, and the first year on the floor, when the hard part is not finding the range but remembering what a number is trying to tell you. On the floor the EMR already flags the range inline, which is why the two right-hand columns exist at all.
Learn the panel, not the row. Values move in patterns. A high BUN next to a high creatinine reads differently than a high BUN with a normal creatinine. Reading across a panel is the skill the exam is testing.
Ranges are a population, not a verdict. A reference range is set so that roughly 95% of a healthy reference group falls inside it, which means healthy people land outside it all the time, and a sick person can sit squarely inside it. The trend across several draws usually says more than any single value.
Critical values belong to your facility. What counts as critical, who gets called, and how fast are set by local policy, and escalation follows your facility's protocol. No page on the internet, including this one, can tell you those thresholds.
Print it. The print button strips the dark background and lays the panels out compactly for a clipboard or a binder. The source line prints with it.
Every reference range on this page is transcribed from Appendix A of an openly licensed nursing textbook: Open Resources for Nursing (Open RN); Ernstmeyer K, Christman E, editors. Health Alterations [Internet]. Eau Claire (WI): Chippewa Valley Technical College; 2024. Appendix A, Normal Reference Ranges. Available from https://www.ncbi.nlm.nih.gov/books/NBK613071/. Retrieved 2026-08-14.
That work is licensed under a Creative Commons Attribution 4.0 International License. The ranges are reproduced here under that license, unmodified except for formatting and the addition of the two "commonly signals" columns, which are not part of the source. The source in turn cites Medscape, Lab values, normal adult (2024), as its own reference.
Panels transcribed: acid base, cardiac, cholesterol panel, coagulation profile, complete blood count and differential, HbA1C, iron, metabolic panel, liver function tests, thyroid hormones, urinalysis, and the miscellaneous group (BNP, CRP, D-dimer, LDH). No other source was used, and no range was written from memory.
The two right-hand columns are ours. They are short, general associations of the kind found in any nursing fundamentals text, written to be memorable rather than exhaustive. They name no drugs, give no doses, and are not directed at any individual result.