OVERVIEW
What is lactate level (blood) lab test?
Lactate is substance made by muscle tissues and is produced when body turns food into energy (cell metabolism). Depending upon pH, it can present in lactic acid form as well, but mostly because of neutral body pH, the lactate form is present in blood. Lactate levels are normally very low in blood & CSF (cerebrospinal fluid). However, if there are inadequate cellular oxygen levels, or primary ways of energy production in body are disrupted, then it leads to excess lactate production by muscle cells/RBCs/brain or other tissues. This laboratory test is used to measure concentration of lactate found in blood.
Why is lactate level (blood) lab test done?
Primarily this test is done to determine lactic acidosis (condition caused by excess lactate levels disrupting body’s acid-base balance). However, it is ordered:
- If someone has condition in which oxygen delivered to cells is decreased i.e. in shock or congestive heart failure.
- In conditions where lactate levels are increased & has signs and symptoms of acidosis
- Having liver or kidney disease
- As initial evaluation in person suspected of sepsis
- To monitor treatment response in sepsis, shock/heart attack, severe congestive heart failure
- To monitor hypoxia (body deprived of oxygen)
- What can happen if there is high lactate?
Having higher than normal lactic acid levels cause condition called lactic acidosis. If severe enough, then it will upset body’s pH balance.
- What is considered normal lactate level?
Levels less than 1.0 mmol/L in both venous & arterial blood is normal lactate.
- What are critical lactate levels?
Normal lactate concentration in blood of unstressed patient is 0.5 to 1 mmol/L, while, in critical illness patient normal lactate levels are less than 2 mmol/L.
- What do blood lactate levels denote?
Having high lactate levels in blood indicates that a disease is causing lactate to accumulate. Also, greater increase in lactate means greater severity in disease condition.
- What are the signs of lactic acidosis?
Signs like abdominal or stomach discomfort, diarrhea, decreased appetite, shallow or fast breathing, unusual sleepiness and tiredness.
INTERPRETATION OF THE RESULTS:
- “Normal” lactate blood level: 0.5 to 1 mmol/L.
- “Mild to moderate” lactate levels: 2 to 4 mmol/L; this is defined as hyperlactatemia where lactate levels are persistently elevated without metabolic acidosis
- “Lactic acidosis” level: > 4 mmol/L; this is defined as high enough levels to cause acid-base imbalance that results in serum pH < 7.35 in association with metabolic acidosis.
- Hyperlactatemia and lactic acidosis occur with increase in lactate production, a decrease in lactate clearance, or due to combination of both.
Elevated lactate levels found are separated into two groups according to mechanism by which they cause lactic acidosis:
- Type A lactic acidosis: common type, includes conditions which cause person to be unable to breathe enough oxygen or cause reduced blood flow, that eventually results in decreased oxygen transport to tissues
- Type B lactic acidosis: includes conditions that reflect excess demand for oxygen or metabolic problems.
The test is performed to detect high lactate levels in blood which can be sign of hypoxia (lack of oxygen) or presence of other conditions leading to excess production or inadequate clearing of lactate from blood.