Immunoglobulin G (IgG)
Test Overview
The Immunoglobulin G (IgG) test measures the level of IgG antibodies in the blood. IgG is the most abundant antibody in the bloodstream and plays a critical role in protecting the body against long-term or chronic infections by neutralizing toxins and pathogens such as bacteria, viruses, and fungi. This test is typically used to assess immune system function, diagnose chronic infections, evaluate autoimmune diseases, and determine past exposure to certain pathogens or vaccines.
Test Uses
- Assess immune status: The IgG test is often used to assess the body’s immunity to certain infections or vaccines, indicating whether the body has been exposed to a pathogen in the past or if immunity has developed.
- Diagnose chronic or past infections: Elevated IgG levels can indicate a chronic infection or a past infection that the immune system has controlled over time.
- Evaluate immune disorders: Low or abnormal IgG levels can suggest immune deficiencies or autoimmune diseases.
- Monitor vaccine response: IgG levels are measured to evaluate the immune response following vaccination for certain diseases (e.g., hepatitis, measles, tetanus).
Immunoglobulin G (IgG) Test Results & Ranges
| Test Component: | Normal Range: | Abnormal (Possible Conditions): |
|---|---|---|
| Immunoglobulin G (IgG) | Adult: 700–1600 mg/dL Children: 400–1500 mg/dL | Low IgG: < 700 mg/dL May indicate immune deficiency or protein loss conditions (e.g., hypogammaglobulinemia, selective IgG deficiency, nephrotic syndrome). High IgG: > 1600 mg/dL Can suggest chronic infections, autoimmune diseases (e.g., rheumatoid arthritis, SLE), or lymphoproliferative disorders (e.g., multiple myeloma). |
Expected Turnaround Time
- Results Available: Typically within 1–3 business days.
Specimen Requirements
- Sample Type: Blood sample (venipuncture).
- Container: Serum separator tube (SST) or plain red-top tube for serum collection.
Collection Instructions
- Fasting: Fasting is not required for this test.
- Medications: Inform your healthcare provider about any medications or supplements you are taking, as certain treatments can affect IgG levels.
- Proper sample collection: Blood should be collected following standard venipuncture procedures.
Test Details
Clinical Use: Immunoglobulin G (IgG) is the most prevalent antibody in the bloodstream and is crucial for the body’s immune response to infections. It helps neutralize toxins, pathogens, and viruses and provides long-term protection against recurrent infections. Low IgG levels can indicate immune deficiencies, making individuals more vulnerable to infections. It may be seen in conditions such as common variable immunodeficiency (CVID) or selective IgG deficiency. High IgG levels can suggest chronic infections that the body has been exposed to over time (e.g., hepatitis, HIV, syphilis), as well as autoimmune diseases where the immune system mistakenly attacks the body’s own tissues (e.g., systemic lupus erythematosus (SLE), rheumatoid arthritis). IgG testing is also used to monitor vaccine responses, especially for vaccines such as measles, tetanus, and hepatitis B. Elevated levels after vaccination indicate a positive immune response and immunity to the disease.
Limitations: IgG levels can be affected by acute infections, autoimmune diseases, and certain medications, which should be taken into consideration during interpretation. This test alone may not be diagnostic of a specific condition. Further testing may be needed to evaluate specific infections, immune deficiencies, or autoimmune diseases. Chronic or persistent infections may cause sustained elevations in IgG, but testing for other immunoglobulins (IgA, IgM) and related markers may help clarify the diagnosis.
The Immunoglobulin G (IgG) test is essential for evaluating the body’s immune response to infections, assessing immune function, and detecting conditions related to immune deficiencies and autoimmune diseases. It is also an important tool for monitoring chronic infections and evaluating vaccination immunity.