At what level of hemoglobin (Hb) and hematocrit (Hct) is a blood transfusion recommended?

Blood Transfusion Thresholds Based on Hemoglobin and Hematocrit

For most hospitalized adult patients who are hemodynamically stable, transfuse red blood cells when hemoglobin falls below 7 g/dL (hematocrit approximately 21%), and for patients with preexisting cardiovascular disease or undergoing cardiac/orthopedic surgery, use a threshold of 8 g/dL (hematocrit approximately 24%). 1, 2

Standard Transfusion Thresholds by Clinical Context

Hemodynamically Stable Patients Without Cardiovascular Disease

• Transfuse at hemoglobin <7 g/dL for hospitalized adults, critically ill patients, and stable medical/surgical patients 1, 2, 3
• This restrictive strategy reduces blood product exposure by approximately 40% without increasing mortality, myocardial infarction, stroke, pneumonia, or thromboembolism 2, 3
• The evidence supporting this threshold comes from 31 randomized controlled trials with 12,587 participants showing no adverse outcomes with restrictive transfusion 2

Patients With Cardiovascular Disease or High-Risk Surgery

• Transfuse at hemoglobin <8 g/dL for patients with preexisting cardiovascular disease, coronary artery disease, or those undergoing orthopedic or cardiac surgery 1, 2, 3
• For patients with active angina, heart failure, or those on beta-blockers, some guidelines recommend a higher threshold of hemoglobin <10 g/dL 3
• The FOCUS trial demonstrated that an 8 g/dL threshold was safe in postoperative patients with cardiovascular disease without increasing mortality or functional impairment 3, 4

Intraoperative Transfusion Thresholds

• Transfuse at hemoglobin 6-7.5 g/dL in patients without increased risk of end-organ ischemia during surgery 3
• For patients on cardiopulmonary bypass with moderate hypothermia: transfuse at hemoglobin <6 g/dL 3
• For patients at risk of critical end-organ ischemia during surgery: transfuse at hemoglobin <7 g/dL 3
• Hematocrit <30% may be used as a trigger in the context of ongoing surgical bleeding 3

Sepsis and Critical Illness

• Transfuse at hemoglobin <7 g/dL once tissue hypoperfusion has resolved, targeting hemoglobin 7-9 g/dL 3
• This recommendation does not apply during the initial 6 hours of septic shock resuscitation when higher targets may be appropriate 3

Symptom-Based Overrides (Transfuse Regardless of Hemoglobin Level)

Always transfuse when patients exhibit signs of inadequate oxygen delivery, even if hemoglobin is above the numerical threshold: 3, 5, 4

• Chest pain believed to be cardiac in origin 3, 5, 4
• Orthostatic hypotension or tachycardia unresponsive to fluid resuscitation 3, 5, 4
• Congestive heart failure 3, 5
• Signs of end-organ ischemia (ST-segment changes on ECG, altered mental status, decreased urine output) 3
• Acute hemorrhage with blood loss >1500 mL 3

Critical Decision-Making Algorithm

The decision to transfuse must incorporate multiple clinical parameters beyond hemoglobin alone: 3

1. Assess hemoglobin/hematocrit as the initial screening parameter 3
2. Evaluate hemodynamic stability: blood pressure, heart rate, response to fluid resuscitation 3
3. Assess for ongoing bleeding: surgical field appearance, drain output, estimated blood loss 3
4. Monitor end-organ perfusion: ECG for ischemic changes, oxygen saturation, urine output, lactate, mixed venous oxygen saturation 3
5. Consider patient-specific factors: cardiovascular disease history, adequacy of cardiopulmonary reserve, intravascular volume status 3

Transfusion Administration Strategy

• Transfuse one unit at a time in the absence of acute hemorrhage, then reassess before giving additional units 5, 4, 6
• Recheck hemoglobin and clinical status after each unit 3
• For massive hemorrhage (>1500 mL blood loss), activate massive transfusion protocols rather than single-unit transfusion 5

Critical Pitfalls to Avoid

Never transfuse when hemoglobin is >10 g/dL as this increases risks of nosocomial infections, multiple organ failure, transfusion-related acute lung injury (TRALI), and transfusion-associated circulatory overload without clinical benefit 5, 4, 6

Never use hemoglobin as the sole trigger for transfusion—this represents a "clock problem" approach that ignores the complexity of anemia management 3, 5, 6

Do not assume all anemia requires transfusion—consider whether the anemia is acute versus chronic, as chronic anemia is better tolerated due to compensatory mechanisms 3, 7

Avoid transfusing prophylactically before procedures unless hemoglobin is below threshold and significant blood loss is anticipated 3

Special Populations

Pediatric Patients

• Transfuse at hemoglobin <7 g/dL for critically ill children who are hemodynamically stable without hemoglobinopathy or cyanotic cardiac conditions 1
• For children with biventricular repair: hemoglobin <7 g/dL 1
• For children with single-ventricle palliation: hemoglobin <9 g/dL 1

Hematologic/Oncologic Disorders

• Transfuse at hemoglobin <7 g/dL for hospitalized patients with hematologic and oncologic disorders, though evidence quality is lower in this population 1

Gastrointestinal Bleeding

• Transfuse at hemoglobin <7 g/dL for acute gastrointestinal bleeding, targeting hemoglobin 7-9 g/dL 5

Evidence Quality and Strength

The restrictive transfusion strategy at 7 g/dL is supported by strong recommendations with moderate-to-high quality evidence from multiple large randomized controlled trials including the landmark TRICC trial (5,000+ patients) and meta-analyses of 45 trials with over 20,000 participants 1, 2, 3. The 8 g/dL threshold for cardiovascular disease is supported by the FOCUS trial and carries strong recommendations with moderate quality evidence 1, 2, 3. These represent the highest quality evidence available in transfusion medicine and should guide clinical practice in the vast majority of patients.