ICU Topics > Lab Values

Lab Values

Patients in the ICU are critically ill and will have many labs drawn throughout their stay. It is important to know normal values and what to look for in the chart — but understand that every situation is case-specific. You may be able to work with a patient outside the standardized range. A patient's lab values can directly affect their ability to tolerate and participate in therapy; use this page to guide your clinical reasoning.

Hematology & Coagulation

  • Purpose: Measures the blood’s ability to carry oxygen

    Normal Range:Males: 13-18 g/dl; Females: 12-16 g/dl

    Abnormal Value: <7 g/dl which can indicate the extent of anemia or polycythemia.

    • Causes can include: renal failure, cirrhosis, burns, hyperthyroidism, or certain systemic diseases

    Clinical Consideration: low hemoglobin indicates that the heart is working harder to oxygenate the body. Consider therapy in bed only. Look at the trend and norms for the particular patient and/or diagnosis. Are there plans for a blood transfusion? Engage in a clinical discussion with the nurse and/or MD as needed.

  • Purpose: measures the percent of red blood cells in the total blood volume. Helpful in diagnosing abnormal hydration levels, anemia, and polycythemia.

    Normal Range: Males: 37-49%; Females: 36-46%

    Abnormal Value: < 24%

    Clinical Consideration: Patients may exhibit weakness, increased fatigue, tachycardia, decreased exercise/activity tolerance, dyspnea on exertion, and heart palpitations. Consider therapy in bed only. Look at the trend and norms for the particular patient and/or diagnosis. Engage in a clinical discussion with the nurse and/or MD as needed.

  • Purpose: the standardized number of when the blood is sufficiently anticoagulated for the patient’s specific condition and considered to be at a therapeutic level

    Normal Range: 0.9-1.1

    • Therapeutic INR will vary based on the diagnosis. You may see a range of 2-3 for patients anticoagulated for a-fib, coronary artery disease, cerebrovascular disease, DVT, or patients following MI

    Abnormal Value: 3.5-5 or >5

    Clinical Consideration:

    • 3.5-5: Look at trends and norms for the particular patient and/or diagnosis. Is the patient anticoagulated? Do they have a mechanical heart valve?

    • >5: There is an increased risk for bleeding. Consider therapy in bed only. Look at trends and norms for the particular patient and/or diagnosis. Is the patient anticoagulated? Do they have a mechanical heart valve? Engage in a clinical discussion with the nurse and/or MD as needed.

  • Purpose: Platelets (thrombocytes) are cell fragments essential for blood clotting. Platelet count is used to assess bleeding risk and guide activity decisions.

    Normal Range: 150,000–400,000/µL

    Abnormal Value: <150,000/µL (thrombocytopenia); critical <20,000/µL

    Clinical Consideration: Low platelet count increases bleeding risk. At <50,000/µL, consider therapy in bed only and avoid high-resistance or high-exertion activity. At <20,000/µL, consult with the team before initiating any therapy. Consider whether the patient is also on anticoagulation, as this compounds bleeding risk. Look at trends and norms for the particular patient and/or diagnosis. Engage in a clinical discussion with the nurse and/or MD as needed.

Infection, Cardiac, & Perfusion

  • Purpose: WBCs are the body's primary immune defense. Abnormal values can indicate active infection, inflammation, or immune compromise, all of which affect the patient's overall medical stability.

    Normal Range: 5,000–10,000/mm³

    Abnormal Value: >10,000/mm³ (leukocytosis) or <5,000/mm³ (leukopenia); critical <2,000/mm³ or >40,000/mm³

    Clinical Consideration: Elevated WBCs may reflect active infection or systemic inflammation — note this alongside fever, vital sign instability, and the patient's clinical presentation. Critically high or low values may indicate severe sepsis or immunocompromise. Therapy may still be appropriate, but context matters. Look at trends and norms for the particular patient and/or diagnosis. Engage in a clinical discussion with the nurse and/or MD as needed.

  • Purpose: Troponins (I and T) are proteins released into the bloodstream when cardiac muscle is damaged. Elevated values indicate myocardial injury and are a key marker for cardiac events in the ICU.

    Normal Range: Troponin I: <0.03 ng/mL; Troponin T: <0.1 ng/mL

    Abnormal Value: Troponin I: >1.5 ng/mL; Troponin T: >0.1 ng/mL and rising

    Clinical Consideration: Elevated and rising troponins suggest active myocardial injury. A rising trend is more concerning than a single elevated value. Defer therapy and consult with the medical team before proceeding. Consider therapy in bed only until the patient is cleared. Look at trends and norms for the particular patient and/or diagnosis. Engage in a clinical discussion with the nurse and/or MD as needed.

  • Purpose: Lactate is a byproduct of anaerobic metabolism. Elevated levels indicate that tissues are not receiving adequate oxygen and are a key marker for sepsis and shock in the ICU.

    Normal Range: 0.5–2.0 mmol/L

    Abnormal Value: 2.0–4.0 mmol/L (elevated); >4.0 mmol/L (critical — severe tissue hypoperfusion)

    Clinical Consideration: Elevated lactate signals systemic stress and compromised perfusion. At >4.0 mmol/L, defer therapy and notify the team. A rising lactate is a red flag even if the number appears borderline. Look at trends and norms for the particular patient and/or diagnosis. Engage in a clinical discussion with the nurse and/or MD as needed.

Electrolytes & Metabolic

  • Purpose: important for neuromuscular function, action potentials, and cardiac muscle contraction and conductivity. Potassium value provides information on renal and adrenal systems as well as acid-base imbalances.

    Normal Range: 3.5-5.0 mEq/l

    Abnormal Value: <3.2 (hypokalemia) or > 5.2 mEq/l (hyperkalemia)

    Clinical Consideration: Look at trends and norms for the particular patient and/or diagnosis. Look at changes in the EKG.

    • Symptoms of hyperkalemia can include: abdominal cramping, nausea, diarrhea, muscle weakness, flaccid paralysis, paresthesias, fatigue, irritability, EKG changes, or cardiac arrest

    • Symptoms of hypokalemia can include: paralytic ileum, decreased peristalsis, abdominal dissension, constipation, muscle weakness, fatigue, leg cramps, paresthesias, disorientation, hypotension, dysrhythmias, or cardiac or respiratory arrest.

  • Purpose: is a determinant of fluid volume in the body. Helps to facilitate nerve conduction, neuromuscular function, and glandular secretion.

    Normal Range: 135-145 mEq/l

    Abnormal Value: <130 (hyponatremia) or > 150 mEq/l (hypernatremia)

    Clinical Consideration: Note any fluid restrictions. Look for any trends and changes in EKG. Also assess for any mental status changes.

    • Symptoms of hypernatremia can include: change in mental status, confusion, ataxia, convulsions, hypertension, tachycardia, pulmonary edema, dyspnea, and respiratory arrest.

    • Symptoms of hyponatremia can include: nausea, vomiting, abdominal cramps, muscle twitching, weakness, lethargy, confusion, hypotension, tachycardia, and seizures.

  • Purpose: Blood glucose reflects the body's ability to regulate blood sugar. Critically ill patients are at high risk for both hypoglycemia and hyperglycemia, both of which can directly affect cognition, function, and safety during therapy.

    Normal Range: 70–100 mg/dL (fasting)

    Abnormal Value: <70 mg/dL (hypoglycemia); >200 mg/dL (hyperglycemia); critical <40 mg/dL or >450 mg/dL

    Clinical Consideration: Hypoglycemia can present as altered mental status, confusion, or weakness — which may mimic neurological changes. Do not begin or continue therapy if the patient is hypoglycemic; notify nursing immediately. Hyperglycemia is common in critically ill patients and may affect fatigue and activity tolerance. Consider whether the patient is on an insulin drip and look at trends. Engage in a clinical discussion with the nurse and/or MD as needed.

  • Purpose: BUN measures urea nitrogen in the blood and reflects kidney function and hydration status. Often reviewed alongside creatinine to assess renal function.

    Normal Range: 6–25 mg/dL

    Abnormal Value: >100 mg/dL (critical)

    Clinical Consideration: Elevated BUN can indicate renal dysfunction, dehydration, or increased protein catabolism (common in critical illness). Review BUN alongside creatinine to get a fuller picture of renal status. Look at trends and norms for the particular patient and/or diagnosis. Engage in a clinical discussion with the nurse and/or MD as needed.

  • Partial Pressure of Oxygen (PaO2)

    Purpose: Pressure of O2 dissolved in arterial blood. Used to monitor pulmonary status and determine how well O2 can move from the lungs into the blood. Measuring PaO2 is the most accurate test for blood oxygen level.

    Normal Range: 80-95 mm Hg

    • For reference an oxygen saturation of 90% is equal to PaO2 of 60 mm Hg

    Abnormal Value: <80 mm Hg (hypoxemia)

    Clinical Consideration:

    • Signs of hypoxemia can include: mental status changes, tachycardia, and lightheadedness. Be sure to monitor vitals, treat activity intolerance, and instruct in breathing exercises as needed.

  • Purpose: Creatinine is a waste product of muscle metabolism filtered by the kidneys. Elevated levels are a key marker for acute kidney injury (AKI) and reduced renal function.

    Normal Range: Males: 0.7–1.3 mg/dL; Females: 0.6–1.1 mg/dL

    Abnormal Value: >1.3 mg/dL; critical >4.0 mg/dL

    Clinical Consideration: Elevated creatinine indicates impaired renal function. Patients with AKI may have electrolyte imbalances — particularly potassium — that affect activity tolerance and cardiac rhythm. Consider whether the patient is on dialysis (CRRT/CVVH), which may further limit mobility. Look at trends and norms for the particular patient and/or diagnosis. Engage in a clinical discussion with the nurse and/or MD as needed.

Blood Gas & Renal

Quick Reference

Hematology & Coagulation

Lab Normal Range Abnormal Value
Hemoglobin M: 13–18 g/dL  |  F: 12–16 g/dL <7 g/dL
Hematocrit M: 37–49%  |  F: 36–46% <24%
INR 0.9–1.1 3.5–5 (caution)  |  >5 (hold)
Platelets 150,000–400,000/µL <150,000/µL  |  critical <20,000/µL

Infection, Cardiac & Perfusion

Lab Normal Range Abnormal Value
WBCs 5,000–10,000/mm³ <5,000 or >10,000/mm³  |  critical <2,000 or >40,000/mm³
Troponin I <0.03 ng/mL >1.5 ng/mL
Troponin T <0.1 ng/mL >0.1 ng/mL and rising
Lactate 0.5–2.0 mmol/L 2.0–4.0 mmol/L (elevated)  |  >4.0 mmol/L (critical)

Electrolytes & Metabolic

Lab Normal Range Abnormal Value
Potassium 3.5–5.0 mEq/L <3.2 or >5.2 mEq/L
Sodium 135–145 mEq/L <130 or >150 mEq/L
Glucose 70–100 mg/dL (fasting) <70 mg/dL (hypoglycemia)  |  >200 mg/dL (hyperglycemia)  |  critical <40 or >450 mg/dL
BUN 6–25 mg/dL critical >100 mg/dL

Blood Gas & Renal

Lab Normal Range Abnormal Value
PaO2 80–95 mmHg <80 mmHg (hypoxemia)
Creatinine M: 0.7–1.3 mg/dL  |  F: 0.6–1.1 mg/dL >1.3 mg/dL  |  critical >4.0 mg/dL

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References

Evangelist, M., & Gartenberg, A. (2016, February 8). Toolkit for developing an occupational therapy program in the ICU. SIS Quarterly Practice Connections, 1(1), 20–22.

Evangelist, M., & Gartenberg, A. (2017). Vitals: A systemic approach to ICU chart review. In H. Smith-Gabai & S. E. Holm (Eds.), Occupational Therapy in Acute Care (2nd ed., pp. 130–131). AOTA Press.

Matthies, M. J., & Smith-Gabai, H. (2017). Laboratory Values. In H. Smith-Gabai & S. E. Holm (Eds.), Occupational Therapy in Acute Care (2nd ed., pp. 149–174). AOTA Press.

Smith-Gabai, H. (2011). Laboratory Values. In H. Smith-Gabai (Ed.), Occupational Therapy in Acute Care (1st ed., pp. 713–738). AOTA Press.