What is the normal range for lactate (lactic acid) levels?

Normal Range for Lactate Levels

The normal range for serum lactate (lactic acid) is ≤2 mmol/L, with values above this threshold considered elevated and potentially indicative of tissue hypoperfusion or other pathological processes. 1

Understanding Lactate Values and Clinical Significance

Normal Range and Interpretation

• Normal serum lactate levels are ≤2 mmol/L in healthy individuals 1, 2
• Values between 2-4 mmol/L represent mild to moderate elevation 3
• Values >4 mmol/L indicate significant hyperlactatemia and are associated with higher mortality 1, 3

Clinical Significance of Different Lactate Levels

• Lactate ≤1.4 mmol/L: Associated with better outcomes in septic shock patients 4
• 1.4-2.3 mmol/L: Though within "normal range," may still indicate increased mortality risk compared to lower values 4
• 2.5-4.0 mmol/L: Associated with 9% mortality in ED patients with infection 3
• ≥4.0 mmol/L: Associated with 28.4% mortality in ED patients with infection 3

Lactate as a Prognostic Indicator

Mortality Prediction

• Even lactate levels within the upper normal range (1.4-2.3 mmol/L) can predict increased mortality compared to lower values (≤1.4 mmol/L) 4
• Lactate clearance (return to normal range) within 24 hours is associated with 100% survival in trauma patients 1
• Delayed normalization (>24 hours) correlates with development of post-traumatic organ failure 1
• Persistent elevation >48 hours is associated with only 13.6% survival 1

Shock and Tissue Hypoperfusion

• Serum lactate serves as an indirect marker of oxygen debt and tissue hypoperfusion 1
• Serial lactate measurements provide early and objective evaluation of a patient's response to therapy 1
• Lactate elevation with simultaneous elevation of lactate/pyruvate ratio (>18) is more strongly associated with mortality (37.5% vs 12.5%) and suggests inadequate tissue perfusion 2

Important Considerations in Lactate Measurement

Sampling Techniques

• Arterial and peripheral venous lactate levels are not interchangeable, especially in hyperlactatemia 5
• Peripheral venous lactate tends to be higher than arterial lactate (mean differences 0.18-1.06 mmol/L) 5
• Peripheral venous lactate can rule out arterial hyperlactatemia with high sensitivity (97-100%) at a cut-off of 2 mmol/L 5

Technical Considerations

• Proper sample handling is critical for accurate results 1:
  • Use prechilled fluoride-oxalate tubes
  • Transport immediately on ice to the laboratory
  • Process within 4 hours after collection
  • Collect blood without using a tourniquet and without fist-clenching 1

Confounding Factors

• Alcohol consumption can increase blood lactate levels, potentially confounding interpretation in trauma patients 1
• In alcohol-associated trauma, base deficit may be a better prognostic marker than lactate 1
• Other factors that can elevate lactate include cerebral hypoxia/ischemia, anaerobic glycolysis, vascular compromise, and metabolism of CSF leukocytes 1

Clinical Applications in Different Settings

Sepsis and Septic Shock

• Lactate normalization is a target for resuscitation in septic shock 1
• Lactate clearance (decrease by at least 10%) is non-inferior to ScvO2 normalization as a resuscitation target 1
• Patients with lactate ≤1.4 mmol/L may benefit from vasopressin infusion in septic shock 4

Trauma and Hemorrhagic Shock

• Serum lactate and base deficit are recommended as sensitive tests to estimate and monitor the extent of bleeding and shock (Grade 1B recommendation) 1
• Both parameters should be assessed independently as they don't strictly correlate with each other in severely injured patients 1