2 Blood Counts and Coagulation
Learn how to interpret complete blood count and coagulation results alongside symptoms, trends, medications, and patient-specific reference ranges, and recognize findings that require prompt escalation.
Interpret results in context
CBC and coagulation results are clues, not diagnoses. Interpret them alongside symptoms, vital signs, trends, medications, and the laboratory’s own reference ranges. Reference ranges vary by laboratory and patient factors, and a mildly abnormal result in a stable patient differs from a rapidly changing result or one accompanied by concerning symptoms.
Complete blood count findings
A measures red blood cells (RBCs), hemoglobin (Hgb), hematocrit (Hct), white blood cells (WBCs), and platelets. It may also include red-cell indices, such as , which describes average RBC size.
For general orientation, adult Hgb is often about in males and in females. WBCs are often about per microliter, and platelets about per microliter. These are examples, not universal cutoffs; use the reference interval on the patient’s report. Anemia is defined using Hgb, Hct, or RBC count and varies by age and sex.
Red cells and anemia
Low Hgb or Hct may suggest anemia, which may result from blood loss, reduced RBC production, or increased RBC destruction. Assess for fatigue, pallor, dizziness, shortness of breath, chest pain, tachycardia, and bleeding, and compare results with prior values. Anemia is a finding that warrants evaluation, not a diagnosis by itself.
High Hgb or Hct may sometimes reflect dehydration or increased RBC production. Consider the clinical picture and hydration status; an isolated result does not establish the cause.
helps describe anemia patterns: a low means smaller-than-average RBCs, while a high means larger-than-average RBCs. These patterns can guide further assessment but do not identify a cause by themselves.
White cells and infection risk
A high WBC count, or leukocytosis, may be associated with infection, inflammation, physiologic stress, certain medicines, or other causes. Assess for infection and the patient’s overall condition; a high WBC alone does not prove infection.
A low WBC count, or leukopenia, may be associated with medicines, infection, reduced bone-marrow production, or other causes. Review the WBC differential and because low neutrophils can greatly increase infection risk. Severe neutropenia is commonly defined as below per microliter. Fever in a patient with known or suspected severe neutropenia requires immediate clinical escalation according to local protocol, even if other symptoms seem mild.
Platelets and bleeding or clot risk
Platelets help form the initial plug that limits bleeding. A low platelet count can cause easy bruising, petechiae, nose or gum bleeding, or prolonged bleeding; serious internal bleeding is also possible. Assess for petechiae, unusual bruising, gum or nose bleeding, blood in urine or stool, and persistent bleeding. Use bleeding precautions as directed and promptly report new or ongoing bleeding.
A high platelet count, or thrombocytosis, may be reactive to another condition or associated with increased clot risk. Assess for possible clot symptoms and report concerning findings; a high count alone does not diagnose a clot. Assess the patient, not just the number.
Coagulation tests and medications
and , also called PTT, assess different parts of the clotting process. is commonly used to monitor warfarin, while may be used to monitor unfractionated heparin. Interpret either result according to the reason for testing, the medication, the ordered therapeutic target, and the laboratory’s range.
An unexpectedly prolonged or means blood may take longer to clot. Consider bleeding risk, medications, liver disease, or other causes; assess for bleeding and report results outside the prescribed target.
An INR below the prescribed warfarin target may mean anticoagulation is inadequate, increasing clot risk. The target depends on the indication, so do not assume one target applies to every patient. An unexpectedly short clotting time should be interpreted in context and followed up as ordered; a test result alone cannot confirm abnormal clotting in the body.
Do not independently stop, start, or adjust anticoagulant medication based only on a result. Follow orders and facility protocol, and promptly escalate critical results or concerning symptoms.
Recognize findings needing prompt action
Escalate promptly for active or uncontrolled bleeding; blood in vomit, urine, or stool; sudden severe headache; new neurologic changes; fainting; or signs of shock. Also escalate fever with severe neutropenia, a rapid or substantial fall in Hgb or Hct—especially with shortness of breath, chest pain, dizziness, or instability—or an abnormal coagulation result accompanied by bleeding. Sudden chest pain, difficulty breathing, or one-sided leg pain and swelling may indicate a clot and require urgent assessment.
A patient with low Hgb who is stable and has no symptoms still needs follow-up and trend review. The same result with new chest pain, shortness of breath, a fast pulse, or visible bleeding needs prompt assessment and escalation. A low total WBC calls for checking the differential and ; fever with a very low is urgent.