From the Guidelines

Increasing Immunoglobulin G (IgG) levels can be achieved through IgG replacement therapy.

IgG replacement therapy is generally indicated for patients with antibody deficiency diseases, including those with low IgG levels [ 1 ].
The dose of IgG replacement therapy can vary, but doses of up to 800 mg/kg/mo have been used in some studies [ 1 ].
In cases of agammaglobulinemia, IgG replacement therapy is often used in conjunction with antimicrobials and careful attention to pulmonary status [ 1 ].
The goal of IgG replacement therapy is to maintain IgG trough levels above a certain threshold, such as 1000 mg/dL [ 1 ].
IgG replacement therapy can be administered intravenously (IVIG) or subcutaneously (SCIG), and the choice of route depends on individual patient needs and preferences [ 1 ].
Regular monitoring of IgG levels and adjustment of the dose as needed is crucial to ensure optimal therapy [ 1 ].

IgG replacement therapy should only be initiated under the guidance of a healthcare professional with expertise in immunodeficiency diseases.
Patients with low IgG levels should be evaluated for underlying causes of immunodeficiency, such as genetic defects or acquired conditions.
IgG replacement therapy is not a cure for immunodeficiency diseases, but rather a treatment to help manage symptoms and prevent infections.

From the Research

To increase IgG levels, several factors should be considered:

IgG therapy is the mainstay for treatment in the majority of primary immune deficiencies 2
The dosage of IgG therapy may need to be adjusted based on individual patient needs, such as growing children, weight loss or gain, pregnancy, and febrile patients or those with gastrointestinal or lung disease 2
Monitoring patients over time includes physical examination, blood counts and chemistry screening tests, and IgG trough levels at 6-12 month intervals 2
A median trough IgG level of 354 mg/dl was found to be protective with 64% sensitivity and 75% specificity in patients with X-linked agammaglobulinemia on replacement therapy with intravenous immunoglobulin 3
An escalation in IVIG dose of 100 mg/kg produced an increase in serum IgG levels by 53.6 mg/dl 3

Several factors can affect IgG levels, including:

Autoimmune diseases, chronic infection, HIV, and excessive alcohol consumption, which are associated with high levels of IgG 4
Steroid therapy, which can lower serum IgG levels 2
Infections, which can be predicted by IgG trough levels in children on replacement immunoglobulin therapy 3

Quantitative serum immunoglobulin tests are used to detect abnormal levels of IgG, IgA, and IgM 5

These tests can help diagnose various conditions and diseases that affect the levels of one or more of these immunoglobulin classes 5
IgG levels can be measured through blood tests, and the results can be used to adjust IgG therapy dosages and monitor patient response to treatment 2, 3