What Are Normal IgG Levels by Age? (Reference Ranges, Meaning, and Treatment Options)

As we age, changes in the immune system can affect how the body responds to infections and disease. One important way to evaluate immune health is by measuring immunoglobulin G (IgG) levels.

IgG is the most abundant antibody in the blood and plays a critical role in fighting bacterial and viral infections [4]. Testing IgG levels can help clinicians diagnose immune deficiencies, monitor chronic conditions, and guide treatment decisions.

What Are Immunoglobulin Levels?

There are five main types of immunoglobulins: IgG, IgA, IgM, IgE, and IgD. This article focuses on IgG, which is produced by plasma cells and is essential for long-term immune protection [4].

IgG levels naturally vary with age and can provide valuable insight into immune system function. Clinicians often use IgG testing both for diagnosis and for monitoring response to treatment.

Significance of Normal Levels of IgG

Measuring IgG levels can help identify immune deficiencies, chronic infections, and certain autoimmune conditions [1,4]. It is also commonly used to evaluate how well the body responds to infections or vaccines.

While IgG testing can support diagnosis, it is not used in isolation. Results must always be interpreted alongside clinical symptoms, medical history, and other laboratory and diagnostic findings.

Normal IgG Levels by Age

A great deal of research has been done regarding what normal levels of IgG should be. Several notable diagnostic labs pay close attention to such studies and base their services upon them. The normal level (or reference value) is used as a reference point by doctors to help diagnose a particular disease.

An adult should have an IgG level of 600–1600 mg/dl [2,6]. Whenever IgG testing is done for diagnosis, medical professionals must keep the patient’s age in mind before drawing any conclusions. The patient should also be tested for normal IgG subclass levels by age. Levels are determined by conventional serum protein electrophoresis.

Below are the reference values for different age groups, according to Exeter Clinical Laboratory [6]. Reference ranges may vary slightly between laboratories, but the following values are commonly cited in clinical practice:

How Does Age Affect the Levels of IgG?

IgG levels are highest at birth due to maternal antibody transfer, then decline during early infancy before gradually increasing as the body matures [4]. Levels typically stabilize and reach adult ranges during adolescence.

What To Do If Levels Are Not Normal

Abnormal IgG levels may indicate an underlying medical condition.

High IgG levels are often associated with chronic inflammation, autoimmune disorders, or persistent infections [1,4].

Low IgG levels (hypogammaglobulinemia) can increase susceptibility to recurrent infections and may result from genetic conditions, certain medications, or chronic illnesses [1,3].

A healthcare provider should evaluate abnormal results to determine the underlying cause.

Suggested Treatment

Treatment depends on the underlying cause of abnormal IgG levels.

For low IgG levels, management may include:

• Treating the underlying condition
• Preventive or therapeutic antibiotics for infections
• Immunoglobulin replacement therapy (IVIG or SCIG) in moderate to severe cases [3,5,7]

For high IgG levels, treatment focuses on managing the associated condition, such as autoimmune disease or chronic infection.

If you’d like to learn more about IVIG, check out our IVIG Patient Resource Hub.

IVIG Dosing

IVIG dosing varies depending on the condition being treated, body weight, and severity of deficiency. Treatment plans are individualized and determined by a healthcare provider [7].

Cost of Treatment

Manufacturing immunoglobulins is a costly process; therefore, IVIG is quite expensive [8]. One way to reduce costs is by getting IVIG infusions at home or at any other location you prefer as an outpatient. Receiving IVIG at home will reduce the overall cost to a good extent compared to receiving infusions in a hospital. Home infusion reduces overhead costs incurred in a hospital, and fewer personnel are involved with the administration.

Diseases Treated With IgG Infusions

IVIG therapy is commonly used in:

• Primary immunodeficiency disorders [1,3]
• Certain autoimmune diseases (e.g., Guillain-Barré syndrome, myasthenia gravis) [5,7]
• Some inflammatory and neurological conditions [5]

Its use in other conditions depends on clinical evidence and specialist recommendations.

Expected Side Effects

Common side effects of IVIG include [7]:

• Headache
• Fatigue
• Fever or chills
• Nausea

Patients may be treated with medications to decrease the incidence of side effects during infusion. Less common but serious side effects may include allergic reactions, kidney dysfunction, or thrombotic events [7]. Patients should be monitored during treatment.

Conclusion

Measuring IgG levels can provide important insight into immune system health [4]. If you experience recurrent infections or symptoms of immune dysfunction, consult a healthcare provider for proper evaluation and treatment.