Plasma Lactate (Lactic Acid) Test

This test is most often indicated for the diagnosis of lactic acidosis, i.e., abnormally high levels of lactic acid. It is performed in individuals experiencing the symptoms of hypoxia (inadequate oxygen) such as:

• Difficulty in breathing or rapid breathing
• Pain in the abdomen
• Muscle weakness
• Sweating
• Paleness
• Nausea
• Coma

Additionally, lactic test is recommended in individuals who exhibit symptoms associated with sepsis, heart attack, shock, kidney failure, uncontrolled diabetes or congestive heart failure.

This test is also performed intermittently to monitor the levels of lactate after the initial diagnosis of elevated lactate levels. Both cerebrospinal fluid and blood lactate levels may be ordered in individuals with symptoms of meningitis such as fever, severe headache, loss of consciousness and delirium.

No special preparation is needed prior to this test. However, the doctor may recommend avoiding activities that lead to physical exertion and further increase in lactic acid levels.

Inform the doctor about any medication that you are taking before the test. Certain medicines such as metformin or drugs for HIV (human immunodeficiency virus) can cause a rise in lactate levels, interfering with the interpretation of test results.

Plasma lactate test is performed on a blood sample collected from a vein in the hand or arm. Sometimes, blood may be collected from an artery. This test may also be performed on cerebrospinal fluid collected from the spinal column. The procedure for cerebrospinal fluid collection is called a spinal tap.

The typical values and interpretations of plasma lactate test results are as follows; however, the results may vary between laboratories as the laboratories may use different measurements and specimens for the test.

Normal results:

Normal value of plasma lactate ranges between 0.5-2.2 mmol/L or 4.5-19.8 mg/dL. 

Normal lactate levels indicate the absence of lactic acidosis, suggesting sufficient supply of oxygen to various parts of the body and the absence of metabolic problems associated with increased demands.

Abnormal results:

Abnormally high levels of plasma lactate suggest some underlying disease that causes accumulation of lactate in the body. The severity of the condition increases with an increased level of lactate. However, detecting increased lactate levels cannot help in diagnosing the disease. Medical history, physical examination and some additional tests are used for the diagnosis of the underlying conditions. The conditions that cause lactic acidosis are divided into two groups based on the mechanism of rise in lactate levels.

• Type A lactic acidosis occurs due to conditions that interfere with breathing.The individual is unable to breathe even in sufficient oxygen, leading to decreased oxygen supply to body tissues. The following conditions cause type A lactic acidosis:

  • Sepsis
  • Congestive heart failure
  • Heart attack
  • Respiratory failure
  • Shock
• Type B lactic acidosis occurs due to excess oxygen demand by the body. The following conditions cause type B lactic acidosis:
  • AIDS (acquired immunodeficiency syndrome)
  • Liver disease
  • Kidney disease
  • Uncontrolled diabetes
  • Leukaemia
  • Strenuous exercise
  • Toxin exposure such as to methanol or cyanide
  • Glycogen storage disease

Very high levels of lactic acid in the cerebrospinal fluid in individuals with symptoms of meningitis suggest bacterial meningitis while a mild increase in lactic acid in the cerebrospinal fluid indicates viral meningitis.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.