What Is IgG on a Blood Test? Guide to Food Sensitivity

IgG (Immunoglobulin G) on a blood test is a measure of antibodies that your immune system produces in response to specific foods. Unlike IgE, which triggers immediate allergic reactions, IgG reflects a delayed immune response that may be linked to food sensitivities. Today, IgG testing remains a popular tool for identifying potential dietary triggers, helping individuals optimize their health through personalized elimination diets.

What Is IgG?

IgG is the most abundant antibody in human blood, accounting for about 75% of serum antibodies. It plays a key role in long-term immunity by remembering past exposures to pathogens. In the context of food sensitivity testing, elevated IgG levels to certain foods indicate that the immune system has recognized those foods as foreign and is mounting a response. This does not mean you are allergic—it suggests a possible intolerance or sensitivity that may contribute to symptoms like bloating, fatigue, brain fog, or joint pain.

How Does IgG Testing Work?

IgG testing typically involves a blood sample, either from a finger prick or a venous draw. The sample is sent to a laboratory, where it is exposed to a panel of food antigens. The lab measures the amount of IgG antibodies bound to each food. Results are reported as numeric values, often categorized as normal, borderline, or elevated. Most panels include 100–200 common foods, including dairy, grains, meats, vegetables, fruits, and additives.

IgG vs IgE: Key Differences

What Does an IgG Positive Result Mean?

A positive IgG result does not diagnose a food allergy. It indicates that your immune system has encountered that food and produced antibodies. Elevated IgG may reflect frequent consumption of a food, a recent infection, or a true sensitivity. The key is to interpret results alongside symptoms and dietary history. Many practitioners use IgG results to design an elimination diet: remove the high-IgG foods for 2–4 weeks, then reintroduce one at a time while monitoring symptoms.

Interpreting IgG Test Results

Results are typically divided into three zones:

• Normal (low IgG): No significant immune response to that food.
• Borderline (moderate IgG): Possible sensitivity; may warrant elimination.
• Elevated (high IgG): Strong immune reaction; likely a trigger food.

It is important to work with a healthcare provider to avoid unnecessary restrictions. Today, updated guidelines emphasize that IgG testing should be used as a screening tool, not a standalone diagnosis.

Who Should Consider IgG Testing?

Ideal candidates include individuals with chronic, unexplained symptoms like irritable bowel syndrome (IBS), migraine, eczema, or fibromyalgia. Also, those who have tried elimination diets without success may benefit from guidance. The test is not recommended for people with severe IgE-mediated allergies, as it does not replace anaphylaxis management.

Limitations and Considerations

Some medical organizations caution against IgG testing due to lack of standardized evidence and potential false positives. However, many functional medicine practitioners and patients report positive outcomes when using IgG results to tailor diets. Today, newer research is exploring the role of IgG4 subclass, which may be more specific to food tolerance. Always choose a reputable lab that reports IgG4 or total IgG, and avoid tests that claim to diagnose “allergies” via IgG alone.

Take the Next Step

Ready to learn more about your own immune responses? Explore our Food Sensitivity IgG Panel to get a comprehensive, 2026-specific analysis of your potential triggers. Our panel includes 170 foods with clear, actionable results to help you start your elimination diet with confidence.