The lactate test is primarily ordered to help determine if someone has lactic acidosis, a level of lactate that is high enough to disrupt a person's acid-base (ph) balance.
Lactic acid is a product of cell metabolism that can accumulate when cells lack sufficient oxygen (hypoxia) and must turn to a less efficient means of energy production, or when a condition causes excess production or impaired clearance of lactate. (See the "What is being tested?" section for more on this.)
Depending on pH, it is sometimes present in the form of lactic acid. However, with the neutral pH maintained by the body, most lactic acid will be present in the blood as lactate.
Lactic acidosis is most commonly caused by an inadequate amount of oxygen in cells and tissues (hypoxia). If someone has a condition that may lead to a decreased amount of oxygen delivered to cells and tissues, such as shock or congestive heart failure, this test can be used to help detect and evaluate the severity of hypoxia and lactic acidosis. It may be ordered along with blood gases to evaluate a person's acid/base balance and oxygenation.
The lactate test may also be used as part of an initial evaluation of someone who is suspected of having sepsis. Typically, if the person's lactate level is above normal limits, treatment will be initiated without delay. If a person with sepsis can be diagnosed and treated promptly, their chances of recovery are significantly improved.
Lactate levels may be ordered at intervals to help monitor hypoxia and response to treatment in a person being treated for an acute condition, such as sepsis, shock or heart attack, or a chronic condition, such as severe congestive heart failure.
A high lactate level in the blood means that the disease or condition a person has is causing lactate to accumulate. In general, a greater increase in lactate means a greater severity of the condition. When associated with lack of oxygen, an increase in lactate can indicate that organs are not functioning properly.
However, the presence of excess lactate is not diagnostic. A health practitioner must consider a person's medical history, physical examination, and the results of other diagnostic tests in order to determine the cause and to diagnose the underlying condition or disease.
A number of conditions can cause elevated lactate levels. They are separated into two groups according to the mechanism by which they cause lactic acidosis.
Type A lactic acidosis, the most common type, may be due to conditions that cause a person to be unable to breathe in enough oxygen (inadequate oxygen uptake in the lungs) and/or cause reduced blood flow, resulting in decreased transport of oxygen to the tissues (decreased tissue perfusion). Examples of type A conditions include:
Shock from trauma or extreme blood loss (hypovolemia)
Rare glycogen storage diseases (such as glucose-6-phosphatase deficiency)
Use of certain drugs such as salicylates and metformin
Exposure to toxins such as cyanide and methanol
A variety of rare inherited metabolic and mitochondrial diseases that are forms of muscular dystrophy and affect normal ATP production (see the Related Pages tab for links to more information on these)
Strenuous exercise, as with marathon runners
When someone is being treated for lactic acidosis or hypoxia, decreasing concentrations of lactate over time reflect a response to treatment.
When someone has signs and symptoms of meningitis, significantly increased cerebrospinal fluid lactate levels suggest bacterial meningitis while normal or slightly elevated levels are more likely to be due to viral meningitis.
The lactate test measures the level of lactate in the blood at a given point in time. A normal lactate level indicates that a person does not have lactic acidosis, that there is sufficient oxygen at the cellular level, and/or that their signs and symptoms are not caused by lactic acidosis.
This article was last reviewed on November 24, 2014. | This article was last modified on February 24, 2015.
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