Immunoglobulin G

recognising and neutralising bacteria, viruses and toxins.

IgG antibodies are produced after infection or vaccination and provide lasting immune memory. They are also capable of crossing the placenta, offering newborns passive immune protection during early life.

This test is commonly used to evaluate immune competence, investigate recurrent infections, and monitor chronic inflammatory or immune-mediated conditions.

Why do I need an Immunoglobulin G test?

Abnormal IgG levels can indicate immune deficiency, chronic infection, autoimmune disease or immune overactivity. Testing helps determine whether the immune system is functioning effectively.

You may need an IgG test if you:

• Have recurrent or severe infections
• Have frequent respiratory infections
• Are being assessed for immune deficiency
• Have chronic inflammatory or autoimmune conditions
• Have unexplained fatigue or poor infection recovery
• Are undergoing broader immunoglobulin testing
• Need assessment of immune response to infection or vaccination

Conditions associated with abnormal IgG levels include:

• Primary or secondary immunodeficiency
• Chronic infections
• Autoimmune disease
• Chronic inflammation
• Certain blood disorders

Benefits of the Immunoglobulin G test

• Assesses long-term immune protection
  Reflects past infection and immune memory.
• Identifies immune deficiencies
  Detects low IgG levels affecting infection resistance.
• Supports investigation of recurrent infections
  Explains poor immune response.
• Clinically established immune marker
  Used in NHS and specialist care.
• Useful in autoimmune disease assessment
  Elevated levels may reflect immune activation.
• Supports comprehensive immune profiling
  Often combined with IgA and IgM testing.
• Monitors immune-related conditions
  Useful for long-term follow-up.
• Simple blood test
  Requires only one blood sample.

Step by step – how the test works

You can access Immunoglobulin G testing UK-wide through two options:

1. Clinic appointment
   Attend your nearest UK clinic, where a healthcare professional will take your blood sample.
2. At-home or hotel visit (£60 extra)
   A qualified phlebotomist comes to your home or hotel, so you don’t need to travel.

Your sample is analysed in an accredited UK laboratory, and results are delivered securely.

Your results explained

Low IgG levels

May indicate immune deficiency, increasing susceptibility to infections.

Typical UK reference range:

• < 7.0 g/L

Normal IgG levels

Suggest adequate immune protection and antibody production.

Typical UK reference range:

• 7.0–16.0 g/L

High IgG levels

May reflect chronic infection, inflammation or autoimmune disease.

Typical UK interpretation:

• > 16.0 g/L

Reference ranges may vary slightly between laboratories.