H. pylori IgG Antibody Test: Normal Levels & Interpretation

When a patient comes to me with gnawing upper abdominal pain, bloating after meals, or a family history of stomach ulcers, my mind often turns to a tiny spiral-shaped bacterium: Helicobacter pylori. One of the most common tools we use to uncover a past or present infection is the H. pylori IgG antibody test. Let me walk you through what this blood test really tells us – and what it doesn’t.

What is H. pylori IgG Antibody?

Immunoglobulin G (IgG) against H. pylori is a type of antibody your immune system produces weeks to months after initial infection. Unlike IgM (which signals acute infection), IgG persists in the blood for years after the bacteria are cleared – and often for a lifetime if the infection remains active.

In my clinic, I use this test mainly for screening or to support a diagnosis when symptoms like dyspepsia or unexplained iron deficiency anaemia are present. However, it cannot distinguish between an active infection and a resolved one.

Why Would Your Doctor Order This Test?

• Persistent stomach pain or burning sensation (dyspepsia)
• Nausea, bloating, or frequent burping
• Diagnosed peptic ulcer disease – to check for H. pylori as the cause
• Unexplained iron deficiency anaemia (the bacterium can cause silent bleeding)
• Family history of gastric cancer (chronic infection increases risk)

How is the Test Performed?

A simple blood draw from your arm – no fasting required. The sample is sent to a lab where it’s tested using enzyme-linked immunosorbent assay (ELISA) or similar techniques. Results usually come back within a day or two.

Reference Ranges for H. pylori IgG Antibody

Reference ranges may vary slightly between laboratories. Always refer to the specific range provided with your results.

What Does a Positive H. pylori IgG Mean?

A positive IgG result tells me that at some point in your life your immune system encountered H. pylori. For many patients – especially those without symptoms – it could be a sign of an old, cleared infection that left behind antibodies. But in the presence of current gastric pain or an ulcer, it strongly suggests active infection. My next step is usually a stool antigen test or a urea breath test to confirm.

Can H. pylori IgG Test Tell If Infection Is Active?

No – and this is the key limitation. IgG remains elevated for years even after successful treatment. If you’ve been treated for H. pylori before and the result is still positive, it doesn’t mean treatment failed. That’s why I use the IgG test only for initial screening, not for monitoring after therapy.

H. pylori IgG During Pregnancy

Pregnancy does not significantly affect the accuracy of the IgG antibody test. However, if you're pregnant and have severe nausea or vomiting (hyperemesis gravidarum), I still recommend discussing symptoms with your obstetrician. H. pylori infection is not a contraindication for pregnancy, but active infection can worsen anaemia. The test is safe – it’s just a blood draw.

Differences Between IgG, IgA, and IgM for H. pylori

IgG is the most commonly measured antibody because it appears a few weeks after infection and stays high. IgA antibodies can also be detected but are less specific and sometimes used in research settings. IgM indicates a very recent infection (first few weeks). In practice, the IgG test covers most clinical scenarios, especially when symptoms have been present for a while.

What Happens After a Positive Result?

If your IgG is positive and you have symptoms, I typically confirm with a non-invasive stool antigen test or a carbon-13 urea breath test. These tests detect current bacterial activity. If that’s positive, we start a course of triple therapy (two antibiotics plus a proton pump inhibitor). After treatment, the follow-up test of choice is the stool antigen test or breath test – not IgG.

When Might You Get a False Positive or Negative?

False positives can occur in people who were infected years ago and successfully treated – the IgG lingers. False negatives are rare but possible very early in infection (before antibodies form) or in immunocompromised patients whose bodies can’t mount a normal antibody response. That's why clinical context matters.

Frequently Asked Questions

• How long does H. pylori IgG stay positive after treatment? It can stay positive for 12–18 months, sometimes longer. This is why we don’t use it to confirm cure.
• Do I need to fast for the H. pylori IgG blood test? No special preparation is needed. You can eat and drink normally.
• Can the test tell if I have stomach cancer? No, it only detects antibodies to H. pylori. Long-term infection is a risk factor, but a positive test alone does not mean cancer is present.