Immunoglobulin G (IgG) Subclass Measurement (Serum/Plasma)

This test measures specific substances, markers, or cells in your body that help your healthcare provider evaluate how well certain organs and body systems are functioning. The results provide important information about your overall health and can help detect, diagnose, or monitor a wide range of medical conditions.

IgG is divided into four subclasses (IgG1, IgG2, IgG3, IgG4), each with distinct roles in immunity. This test evaluates the concentration of these subclasses in your blood. Variations can indicate immune system health, response to vaccines, or underlying conditions like autoimmune diseases.

Your healthcare provider may recommend this test if you are experiencing symptoms that need an explanation, if you have an ongoing condition that requires regular monitoring, or as part of a routine checkup. It can also be used to see how well a treatment is working or to screen for potential health concerns before symptoms appear.

Your healthcare provider may order this test if you have symptoms like frequent infections, unusual fatigue, or if you’re being treated for conditions like lupus, rheumatoid arthritis, or immune deficiencies. It can also help assess vaccine responses or monitor immune-related treatments.

Depending on the type of test, a small sample of blood, urine, or other body fluid may be collected at a laboratory, clinic, or hospital. Some tests require simple preparation, such as fasting for a certain number of hours or avoiding certain foods and medications beforehand. Your provider will give you specific instructions, and following them carefully helps ensure accurate results.

A blood sample is taken from a vein, usually in your arm. The blood is processed to separate serum or plasma for testing. This test is typically done on a small blood sample sent to a lab for analysis.

Before the test, your healthcare provider will review your medical history, current medications, and any allergies you may have. You may be asked to drink plenty of water, avoid eating for a set period, or temporarily pause certain supplements. Wear comfortable clothing, allow extra time for check-in, and ask questions about anything that is unclear.

No special preparation is needed, but avoid eating or drinking for 2–4 hours before the blood draw if instructed. Wear loose clothing and inform your provider if you’re on blood-thinning medications or have a history of bleeding issues.