IgG
Also known as: Immunoglobulin G
What Does IgG Measure?
IgG (Immunoglobulin G) is a blood test that measures the concentration of Immunoglobulin G antibodies in your bloodstream. These are the most abundant type of antibody in human blood, making up approximately 70-80% of all circulating antibodies. IgG is produced by plasma cells (a type of white blood cell) and plays a central role in the 'memory' component of your immune system — it is the antibody type that remains in your blood long after you've been exposed to an infection or received a vaccine.
Why Does IgG Matter?
IgG levels are a critical indicator of your immune system's health and its ability to fight off bacterial, viral, and other infections. Abnormally low IgG levels (hypogammaglobulinemia) can leave you vulnerable to recurrent or severe infections, while abnormally high levels may signal chronic infections, autoimmune disorders, or certain blood cancers such as multiple myeloma. Clinicians use IgG measurements to diagnose primary immunodeficiency disorders, monitor immune function in patients on immunosuppressive therapy, evaluate suspected autoimmune diseases, and assess the effectiveness of immunoglobulin replacement therapy.
Normal Ranges
Males
700–1,600 mg/dL (7.0–16.0 g/L)
Females
700–1,600 mg/dL (7.0–16.0 g/L)
Children
Varies by age: newborns 636–1,606 mg/dL (maternal IgG); 1–3 months 218–610 mg/dL; 4–6 months 228–636 mg/dL; 7–12 months 353–1,043 mg/dL; 1–3 years 422–1,292 mg/dL; 4–6 years 460–1,255 mg/dL; 7–12 years 570–1,470 mg/dL; 13–18 years 680–1,620 mg/dL
Causes of High Levels
- Chronic or recurrent bacterial and viral infections (e.g., HIV, hepatitis B or C, tuberculosis)
- Autoimmune diseases such as lupus (SLE), rheumatoid arthritis, or Sjögren's syndrome
- Multiple myeloma or other plasma cell disorders (monoclonal IgG spike)
- Liver disease including chronic hepatitis or cirrhosis
- Inflammatory bowel disease (Crohn's disease or ulcerative colitis)
- Sarcoidosis or other chronic granulomatous diseases
Causes of Low Levels
- Primary immunodeficiency disorders such as Common Variable Immunodeficiency (CVID) or X-linked agammaglobulinemia
- Protein-losing conditions such as nephrotic syndrome or protein-losing enteropathy
- Certain blood cancers including chronic lymphocytic leukemia (CLL) or lymphoma
How to Improve Your IgG
Diet
- Consume adequate high-quality protein (1.0–1.2 g/kg body weight daily) from sources like lean meats, fish, eggs, legumes, and dairy to support antibody synthesis
- Eat foods rich in zinc such as oysters, beef, pumpkin seeds, and lentils, as zinc is essential for B-cell and plasma cell function
- Include vitamin C-rich foods (citrus fruits, bell peppers, broccoli) to support lymphocyte production and antibody response
- Incorporate fermented foods like yogurt, kefir, and sauerkraut to promote gut microbiome health, which is closely linked to immune function
- Reduce ultra-processed foods, refined sugars, and trans fats, which can promote systemic inflammation and impair immune regulation
Supplements
- Zinc: 8–11 mg/day (RDA) or up to 25–40 mg/day short-term under medical supervision to support B-cell and antibody production
- Vitamin D3: 1,000–2,000 IU/day (or as directed by a physician based on blood levels) to modulate immune function and support IgG production
- Vitamin C: 500–1,000 mg/day to enhance lymphocyte activity and antibody synthesis
- Immunoglobulin replacement therapy (IVIG or SCIG): prescribed by a physician for clinically diagnosed IgG deficiency, typically dosed to maintain trough IgG levels above 500 mg/dL
Related Biomarkers
Frequently Asked Questions
What does it mean if my IgG levels are low?
Low IgG levels (below 700 mg/dL in adults) indicate that your immune system may not be producing enough protective antibodies. This condition is called hypogammaglobulinemia and can result in frequent, severe, or unusual infections — particularly bacterial infections of the respiratory tract. Causes range from inherited immune deficiencies (like CVID) to acquired conditions like blood cancers, protein-loss disorders, or side effects of certain medications. If you have low IgG and recurring infections, your doctor may recommend immunoglobulin replacement therapy.
Can high IgG levels indicate cancer?
Yes, significantly elevated IgG can sometimes indicate a plasma cell malignancy such as multiple myeloma or Waldenström's macroglobulinemia. In these conditions, a single abnormal clone of plasma cells produces massive amounts of a single type of IgG antibody, which appears as a sharp 'M-spike' on a serum protein electrophoresis (SPEP) test. However, high IgG more commonly results from benign causes such as chronic infection or autoimmune disease. A doctor will use additional tests — including SPEP, immunofixation, and free light chains — to rule out malignancy.
How is IgG different from IgA, IgM, and IgE?
Each immunoglobulin class has a distinct role. IgG is the most abundant and provides long-term 'memory' immunity after infections or vaccinations. IgM is the first antibody produced in response to a new infection and is a marker of acute or recent exposure. IgA is found mainly in mucosal areas (saliva, tears, gut lining) and is the body's first line of defense at entry points. IgE is present in very small amounts and is primarily associated with allergic reactions and responses to parasites. Testing all four together gives a comprehensive picture of immune function.