Definition

A lactic acid test measures the concentration of lactic acid in the blood. Lactic acid is produced by muscle tissue and red blood cells when oxygen is delivered from the lungs throughout the body. It is generated during the conversion of carbohydrates into energy, a process essential during periods of low oxygen availability. Under normal circumstances, lactic acid levels in the blood remain low.

Elevated lactic acid levels may indicate oxygen deficiency (hypoxia) or other conditions that lead to increased production or impaired clearance of lactic acid. Such oxygen insufficiency can arise during strenuous physical activity or as a result of illness or infection. Additionally, conditions that heighten lactic acid production or inhibit its removal can further contribute to elevated levels.

Indications

A lactic acid test is primarily used to diagnose lactic acidosis, a condition characterized by abnormally high levels of lactic acid in the blood. It also helps assess oxygen delivery to tissues and assists in diagnosing sepsis, a life-threatening condition caused by bacterial infections. Symptoms of lactic acidosis include:

• Muscle weakness
• Rapid breathing
• Vomiting
• Sweating
• Coma

Contraindications

There are no specific contraindications for a lactic acid test. It can be performed on anyone if needed.

Preparation Before the Test

Preparing for this test requires fasting and avoiding strenuous activities. Generally, you will be instructed not to exercise or engage in certain activities for several hours before the test, as this could elevate lactic acid levels and affect the results. Fasting for approximately 8–10 hours prior to the test is also typically required.

Inform your doctor if you are undergoing treatments that involve regular use of certain medications, especially if you are a patient with HIV or type 2 diabetes. For example, the diabetes medication metformin may increase lactic acid levels due to its association with the risk of lactic acidosis, potentially influencing test results.  

Test Procedure

The lactic acid test typically requires a blood serum sample of 0.25–0.5 ml, collected from a vein. The blood sample is drawn into a specialized tube for analysis. Laboratory personnel use gloves and other personal protective equipment (PPE) during the procedure to ensure safety.

Before drawing blood, the technician applies an elastic band to the arm and cleans the needle insertion site with antiseptic gauze. Blood is usually taken from a vein in the elbow crease. Once the blood is collected into the tube, the elastic band is removed, and the puncture site is pressed and cleaned with antiseptic gauze. This procedure takes only a few minutes. The collected blood sample is then analyzed in a laboratory using specialized equipment, with results typically available within a few hours.

Normal and Abnormal Values

The typical range of normal lactic acid levels in the blood is approximately 4.5 to 19.8 mg/dL. Levels exceeding this range are considered elevated, while levels below this threshold are classified as reduced. However, slight variations in reference ranges may occur between laboratories due to differences in equipment and testing methods.

Results and Recommendations (Further Testing)

Normal

A lactic acid test result within the normal range signifies that the body is maintaining proper balance and function, with adequate oxygen delivery to cells. This indicates the absence of lactic acidosis. To maintain good health, consider adopting a balanced diet, engaging in regular physical activity, and scheduling periodic health evaluations.

High

Elevated lactic acid levels may indicate lactic acidosis, which is categorized into two types, namely Type A and Type B, based on the underlying cause.

Type A lactic acidosis is associated with conditions that impair oxygen delivery to the body, such as breathing difficulty. While type B lactic acidosis is linked to metabolic issues that increase the body's oxygen demand, often due to specific medical conditions.

In meningitis cases, high lactic acid levels may indicate a bacterial infection, while normal or slightly elevated levels suggest a viral infection. Additionally, vitamin B1 deficiency may also contribute to elevated lactic acid levels.

Consult the Right Doctor

If your lactic acid test results are abnormal, consult a general practitioner to obtain an accurate diagnosis and appropriate therapy. An internist may be recommended for further evaluation if necessary. For pediatric patients, consulting a pediatrician will provide more tailored advice and treatment.

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