Blood Test for Lactic Acid
The blood test for lactic acid is a direct measurement of lactate concentration in blood, which can be obtained from arterial, venous, or mixed venous blood samples, with arterial blood being the gold standard. 1, 2
Blood Sample Types for Lactate Measurement
Arterial blood sampling is the preferred method for lactate measurement:
- Arterial lactate is considered the gold standard for assessing tissue perfusion and metabolic acidosis 2
- Direct blood sampling through arterial puncture allows measurement of lactate concentration in blood 1
- The rise in lactate in blood is most easily detectable compared to intracellular or interstitial levels 1
Venous blood can also be used:
- Peripheral venous blood sampling is acceptable and commonly used in clinical practice 1
- Mixed venous blood provides information about overall tissue oxygen extraction and metabolism 2
- Both arterial and peripheral venous blood can be used to obtain base deficit values, which correlate with lactate 1
Clinical Testing Methods
Laboratory measurement:
- Blood lactate is measured directly from blood samples as part of standard laboratory testing 1
- The test is routinely available and has been used as a diagnostic marker since the 1960s 1
- Serial measurements (repeated testing over time) are recommended for monitoring shock and tissue hypoperfusion 1
Point-of-care testing:
- Multiple point-of-care analyzers are available for rapid lactate measurement at the bedside 3
- These devices provide results within 3-180 seconds and can measure lactate concentrations ranging from 10 to 2000 µM 4
Alternative When Lactate Cannot Be Measured
Base deficit from arterial blood gas analysis serves as an acceptable alternative:
- Standard bicarbonate, routinely reported with arterial blood gases, can be used when lactate cannot be measured 1
- Bicarbonate decreases almost reciprocally with lactate increase 1
- Base deficit values provide an indirect estimation of global tissue acidosis due to impaired perfusion 1
Important Clinical Caveats
Reliability considerations:
- Lactate determination may be less reliable when traumatic injury is associated with alcohol consumption, as alcohol can increase blood lactate levels independently of tissue perfusion 1, 2
- Multiple blood samples may be required in exercise testing contexts to determine the point of lactate rise accurately 1
- Normal lactate clearance rate in healthy subjects is approximately 320 mmol/L/hr, primarily through liver metabolism 4