Celiac Disease IgG Test: Results, Ranges & Online Interpretation

Celiac disease IgG testing detects immune response to gluten triggering intestinal inflammation and malabsorption. IgG tissue transglutaminase antibodies indicate gluten sensitivity and potential celiac disease. Understanding celiac test results guides dietary management and health optimization for those with gluten sensitivity.

How to interpret your IgG celiac test results

An IgG celiac antibody test screens for an immune response to gluten when standard IgA-based tests are not appropriate. The two most commonly ordered IgG-class assays are tissue transglutaminase IgG (tTG-IgG) and deamidated gliadin peptide IgG (DGP-IgG). Results fall into three reporting categories: negative, positive, and uncertain or indeterminate.

A negative result suggests celiac disease is unlikely but does not fully rule it out: about 2% to 3% of celiac patients are seronegative. A positive result suggests celiac disease may be present and should trigger a confirmatory workup before any dietary changes are made. An uncertain result usually prompts additional testing.

How IgG performance differs from IgA

The two isotypes do not perform the same. Across guideline reviews, tTG-IgA reaches roughly 98% sensitivity and 98% specificity, while tTG-IgG sits closer to 70% sensitivity and 95% specificity. DGP-IgG performs slightly better than tTG-IgG — about 80% sensitivity and 98% specificity. The IgG variants are therefore lower-yield as a first-line screen but useful in specific situations.

Performance ranges adapted from Leffler and Schuppan as cited in the underlying guideline review.

A key interpretation rule comes from NIDDK: if a tTG-IgG result is positive in isolation and the patient does not have IgA deficiency, the test is considered rather inaccurate. Some laboratories build this into a cascade — total IgA is measured first, and tTG-IgG plus DGP-IgG are used only when total IgA is deficient, specifically to avoid stand-alone tTG-IgG false positives.

Why IgG testing is ordered: the IgA-deficiency context

The reason an IgG-class celiac test exists is selective IgA deficiency. People with this condition do not produce enough IgA to make an IgA-based celiac panel reliable, so the assay can return a falsely negative result even when celiac disease is present.

The numbers explain why this matters for celiac screening:

• Selective IgA deficiency is found in roughly 1 in 400 to 1 in 800 people in the general population.
• Among people with celiac disease, IgA deficiency is far more common — about 2% to 3%.
• Patients with celiac disease are estimated to be 5 to 10 times more likely to have selective IgA deficiency than the general population.

Because of this overlap, total IgA is usually measured alongside any celiac panel, and some labs add total IgA automatically when tTG antibody testing is ordered. When total serum IgA falls below 0.2 g/L, an IgG-based screening test is performed instead — most often DGP-IgG, with tTG-IgG as an alternative.

Other situations that favor an IgG-based assay

Beyond confirmed IgA deficiency, IgG-class assays come into play when serology in young children is unreliable. The sensitivity of IgA-based tests drops in children younger than 2, so combining DGP (IgA and IgG) with tTG-IgA is recommended in that age group. NIDDK echoes the same point. This page covers IgG-specific testing; for the standard first-line IgA workflow, see the IgA celiac test page.

The IgG celiac antibody panel: tTG-IgG, DGP-IgG, EMA-IgG, AGA-IgG

A lab requisition may list more than one IgG-class antibody. Knowing which one was ordered — and why — matters for interpretation.

tTG-IgG (tissue transglutaminase IgG)

Tissue transglutaminase is an intestinal enzyme that modifies gluten-derived peptides. The IgG variant of the anti-tTG antibody is most often ordered to help diagnose celiac disease in patients who have IgA deficiency. Outside that setting, NIDDK states the tTG-IgG test is not useful.

DGP-IgG (deamidated gliadin peptide IgG)

DGP-IgG targets a chemically modified fragment of gliadin. The IgG-based DGP antibody is slightly more sensitive than the IgG-based tTG antibody and is the test of choice in patients with selective IgA deficiency. NIDDK gives the same recommendation. DGP is also frequently combined with IgA-based tests in children younger than 2.

EMA-IgG (endomysial antibody IgG)

EMA testing is an immunofluorescence assay rather than an ELISA — more expensive and time-consuming to run, with a qualitative readout that introduces some interobserver variability. An IgG version exists, but in routine practice the IgA-based EMA is the one used after a positive tTG to make a celiac diagnosis more certain.

AGA-IgG (anti-gliadin IgG)

Anti-gliadin antibody was the first celiac serologic test developed in the 1980s. Because of its relatively low sensitivity and specificity, it should not be used to screen for celiac disease. A positive AGA-IgG in isolation, without supportive tTG or DGP findings, is not diagnostic.

How to prepare for the test (the gluten challenge)

The single most important preparation rule is also the easiest to overlook: you must be eating gluten regularly when the blood is drawn. If the test is being used to diagnose celiac disease, MedlinePlus advises continuing to eat foods containing gluten for a few weeks before testing, following the ordering provider’s instructions. NIDDK is equally direct: for accurate diagnostic results, the patient must be on a gluten-containing diet.

What happens if you’ve already started a gluten-free diet

Antibody levels drop on a gluten-free diet, and how quickly they fall varies from weeks to months. If a patient has been gluten-free for only about a month, it is reasonable to obtain a tTG antibody measurement immediately — a positive result still strongly suggests celiac disease. If the patient agrees to a small intestinal biopsy, gluten should be resumed for several weeks beforehand and a gastroenterology referral made. A gluten-free diet should not be started before diagnosis is confirmed, because the intestinal mucosa will begin to heal and complicate biopsy interpretation.

The blood draw itself

The blood draw is straightforward. A healthcare professional collects a small sample of blood from a vein in your arm with a small needle, typically in less than five minutes. There is no fasting requirement and very little risk — at most slight pain or bruising at the puncture site, which usually resolves quickly.

Next steps after a positive IgG celiac result

A positive serologic result is a screening signal, not a diagnosis. Serologic tests are intended for screening and do not confirm a celiac diagnosis on their own. The standard next step in adults is referral to a gastroenterologist for upper GI endoscopy with duodenal biopsies — NIDDK specifies that biopsies should sample both the duodenal bulb and the distal duodenum.

A no-biopsy pathway exists for selected pediatric cases. The European Society for Paediatric Gastroenterology, Hepatology and Nutrition proposed that a symptomatic child may avoid biopsy only if all three criteria are met. These are: tTG antibody greater than 10 times the upper limit of normal, a positive endomysial antibody, and positive HLA-DQ2 or HLA-DQ8 testing. NIDDK notes a similar pathway is sometimes used when adult endoscopy is not feasible, but adds that this practice has not been endorsed in adult gastroenterology.

The role of HLA-DQ2/DQ8 testing

Genetic testing is not used to make a positive celiac diagnosis, because roughly 30% of the general population carries HLA-DQ2 or HLA-DQ8 and only a small fraction develop celiac disease. The strength of HLA testing is its negative predictive value: a result negative for both HLA-DQ2 and HLA-DQ8 essentially excludes celiac disease. HLA testing is useful when biopsy results are equivocal, or when a patient has self-started a gluten-free diet without prior serology.

Other testing your doctor may add

MedlinePlus lists several follow-up tests after a positive serology: small-intestine or skin biopsy (if dermatitis herpetiformis is suspected), capsule endoscopy, genetic testing, and tests for downstream complications such as anemia, osteoporosis, or specific vitamin deficiencies. Long-term follow-up for confirmed celiac disease typically includes thyroid function testing and liver transaminase measurement every 1 to 2 years. Patients with celiac disease are at increased risk for autoimmune thyroid disease, autoimmune hepatitis, and type 1 diabetes. The same logic supports periodic checks on related markers such as ferritin, vitamin B12, and vitamin D, all of which can be affected by malabsorption.

When to talk to your doctor

A celiac IgG result — positive, negative, or uncertain — is meant to be interpreted by a clinician who knows your full picture. Specific situations that warrant a follow-up conversation include:

• Any positive or uncertain IgG celiac result, before making any dietary changes. A gluten-free diet should not be started before diagnosis is confirmed by biopsy, because it will obscure the histology.
• A negative IgG result with persistent symptoms or strong clinical suspicion. About 2% to 3% of celiac patients are seronegative, and additional workup — biopsy, HLA testing, or further serology — may still be appropriate.
• A positive tTG-IgG alone in someone who does not have IgA deficiency. NIDDK notes an isolated tTG-IgG positive in an IgA-sufficient patient is often a false positive, and clarification with total IgA and tTG-IgA is warranted.
• Dermatitis herpetiformis — a chronic, severely itchy, blistering rash that is the cutaneous form of celiac disease. A skin biopsy can confirm the diagnosis.
• Unexplained iron-deficiency anemia, bone loss, transaminase elevation, or peripheral neuropathy alongside any positive or uncertain celiac serology.
• A positive over-the-counter home or fingerstick celiac test. Caution is warranted in making a diagnosis from a home result alone; confirmation with standard lab testing and clinician-guided workup is essential.

Frequently asked questions

Why did my doctor order IgG instead of IgA?

The IgG variant is typically ordered when IgA-based testing is unreliable. The most common reason is selective IgA deficiency, which is 5 to 10 times more common in people with celiac disease than in the general population. In IgA-deficient patients, IgG-based tests can help with diagnosis where IgA tests cannot.

Is DGP-IgG more accurate than tTG-IgG?

For most patients, yes. The IgG-based DGP antibody is slightly more sensitive than the IgG-based tTG antibody and is the test of choice in patients with selective IgA deficiency. NIDDK gives the same recommendation.

What does an isolated positive tTG-IgG mean if my IgA is normal?

It is often a false positive. NIDDK states that if tTG-IgG alone is positive and the patient does not have IgA deficiency, the test is rather inaccurate. Most labs handle this by measuring total IgA first and only using tTG-IgG when IgA is deficient.

Can IgG testing diagnose non-celiac gluten sensitivity?

No. Non-celiac gluten sensitivity has no validated biomarker — the tTG antibody is absent and there is no villous atrophy. Diagnosis is reached by excluding celiac disease and observing symptom response to gluten withdrawal.

Do I need to be eating gluten before the test?

Yes. For accurate diagnostic results, you must be on a gluten-containing diet. MedlinePlus recommends continuing gluten-containing foods for a few weeks before testing, following your provider’s specific instructions.

How soon will my IgG levels drop after starting a gluten-free diet?

In most patients on a strict gluten-free diet, antibody titres normalize after 6 to 12 months, though speed varies with initial titre and disease severity. Persistently positive titres strongly suggest ongoing gluten exposure, often from dietary contamination.

What’s the difference between tTG-IgG, DGP-IgG, EMA-IgG, and AGA-IgG?

They target different antigens with different performance. tTG-IgG (~70% sensitivity) and DGP-IgG (~80%) are the IgG-class workhorses; EMA-IgG is qualitative and rarely used in routine practice; AGA-IgG is the legacy assay and is not recommended for screening.

Are home or fingerstick celiac tests reliable?

They can detect tTG antibody from a fingertip sample, but caution is warranted with a home result alone. There is concern that people may self-diagnose and start a gluten-free diet without proper confirmation or dietary counseling.

References

• MedlinePlus (U.S. National Library of Medicine, NIH)
• Peer-reviewed reference
• PubMed (U.S. National Library of Medicine, NIH)

Last reviewed: 2026-05-13