Skip to content
Blood Test Tracker

IA-2 Antibody (Islet Antigen-2)

Measures antibodies to IA-2, a protein in insulin-making cells, which is one of the islet antibodies used to look for autoimmune (type 1) diabetes.

AI-verified against cited sources. Awaiting expert reviewAlso called IA-2, IA-2A, IA2LOINC 56718-0

Check your result

Sex (optional)

Type your result to see where it falls.

Nothing you type here leaves your browser.

What it is

IA-2 (islet antigen-2) is a protein found in the insulin-making cells of the pancreas. In some people the immune system makes antibodies against it. This test measures how much of that antibody is in your blood. Many labs call a value of 7.5 units per milliliter or higher positive, but kits differ, so the cutoff printed on your own report is the one to use.

Why it matters

IA-2 antibody is one of four islet antibodies (GAD65, IA-2, insulin and ZnT8) used to find autoimmune, or type 1, diabetes. Having two or more of them, even with normal blood sugar, is called stage 1 type 1 diabetes. IA-2 antibodies are rarely the first one to appear, but when they are present, people tend to progress faster. Doctors use the results to support a diagnosis of autoimmune diabetes and to decide how closely to follow someone. ARUP notes the test is most useful once type 1 diabetes has been diagnosed and advises against using it alone to tell type 1 from type 2 diabetes.

If it’s high

A positive result means IA-2 antibodies were found. In someone with diabetes, this can be a sign of an autoimmune cause (type 1 diabetes), but one test does not settle the type of diabetes. In someone without diabetes, a single positive antibody is not a diagnosis, and a first positive is usually confirmed with a second test. IA-2 antibodies are linked to a faster move toward symptoms, so your clinician may suggest closer follow-up if you also have other islet antibodies.

Common causes

  • A single low-level positive that later goes away (up to half of children with one antibody become negative later)
  • Type 1 diabetes, including slow-onset forms in adults (LADA)
  • Stage 1 or stage 2 type 1 diabetes found by screening, for example in relatives of people with the condition

What can help

  • Ask whether a second test, or the other islet antibodies (GAD65, ZnT8 and insulin), should be checked to confirm the result
  • If you have diabetes, ask whether this result changes how your diabetes is classified or followed
  • Ask for information on the signs of high blood sugar, such as strong thirst, frequent urination and weight loss, so you know when to call

Usual ranges

What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.

For adults: 0–7.4 U/mL. Source: ARUP Laboratories, Mayo Clinic Laboratories (Extended Catalog mirror, testcatalog.org), Diabetes, Obesity and Metabolism 2026;28:4409-4412.

What can affect your result

  • Kit and cutoff: ELISA kits use different thresholds, and radiobinding assays use a different scale
  • Age: islet antibodies usually first appear in early childhood
  • Family history of type 1 diabetes
  • Time since diagnosis: the antibodies can fade after type 1 diabetes starts
  • Methods differ. ELISA results (U/mL) and radiobinding assays (reported in other units, such as NIDDK units) are on different scales and cannot be compared directly.
  • Different ELISA kits use different cutoffs (7.5 U/mL at ARUP and Esoterix, 5.4 U/mL for the Quest assay), so a value between the two can be positive at one lab and negative at the other.
  • ARUP rejects plasma, frozen serum separator tubes and grossly hemolyzed, icteric or lipemic samples.

Levels change slowly. After type 1 diabetes is diagnosed, the antibodies fade in some people: in one UK study followed for a median of about 7 years, about 77% of those positive at diagnosis were still IA-2-positive.

When to talk to a clinician

Seek emergency care if you have very high blood sugar together with vomiting, belly pain, fast or deep breathing, fruity-smelling breath or confusion. These can be signs of diabetic ketoacidosis. Contact a clinician soon for new constant thirst, frequent urination or weight loss.

Questions you could ask

  • Why was this test ordered, and what will we do with the result?
  • Does my lab's cutoff differ from other labs, and how should I compare future results?
  • Should we repeat this test or check the other islet antibodies?
  • Does this result change how my diabetes is classified or followed?
  • How often should my blood sugar or A1c be checked from now on?

Questions people ask

Why does my lab show a different cutoff than another lab?

Labs use different ELISA kits. ARUP and the Esoterix lab call 7.5 U/mL or more positive, while the Quest assay listed by Mayo uses 5.4 U/mL. A result between those two numbers can be positive at one lab and negative at the other. Compare your result with the range on your own report.

If only my IA-2 antibody is positive, do I have type 1 diabetes?

Not by itself. Type 1 diabetes in the early stages is defined by two or more islet antibodies. Studies show that most people with one antibody do not develop diabetes within 10 years, although IA-2 as the only antibody carries somewhat more risk. Your clinician may repeat the test and check the others.

Show the science and sources

For clinicians and researchers

IA-2 (ICA512, a protein tyrosine phosphatase-like protein) autoantibodies are one of four islet autoantibodies used to classify and stage type 1 diabetes. The ADA defines stage 1 as two or more islet antibodies with normal glucose and stage 2 as the same antibodies with dysglycemia, with 5-year risks of symptomatic disease of about 44% and 75%. IA-2 autoantibodies are rarely the first to appear in at-risk children. Higher titers of IA-2 and insulin autoantibodies are associated with earlier onset. IA-2 or ZnT8 positivity is associated with faster progression than when both are absent. In first-degree relatives, IA-2 or ZnT8 seroconversion carries a 5-year progression rate of about 45%, and one of them is found in 78% of progressors (Insel 2015). Among people with a single antibody, progression is more common in children under 5, with IA-2 as the single antibody, or with high-affinity antibodies. The ADA recommends confirming a first positive within 3 months, preferably in a lab that meets Islet Autoantibody Standardization Program standards. The Quest-listed ELISA is standardized against WHO Reference Reagent 97/550, and the RSR IA-2 ELISA version 2 has a manufacturer positivity threshold of 7.5 U/mL and a measuring range of 0.95 to 4000 U/mL on undiluted serum. Radiobinding assays report in NIDDK units, which differ from ELISA U/mL.

LOINC 56718-0 (primary), 31209-0, 70253-0. Specimen: serum.

Sources

  1. Islet Antigen-2 (IA-2) Autoantibody, Serum (ARUP test 3001499), ARUP Laboratories (2026)
  2. IA2 Autoantibodies (Mayo Clinic Laboratories test FIAAB), Mayo Clinic Laboratories (Extended Catalog mirror, testcatalog.org) (2026)
  3. IA-2 Antibody (Mayo Clinic Laboratories test FIA2A), Mayo Clinic Laboratories (Extended Catalog mirror, testcatalog.org) (2026)
  4. Diabetes Autoimmune Profile (Mayo Clinic Laboratories test FDAIP), Mayo Clinic Laboratories (Extended Catalog mirror, testcatalog.org) (2026)
  5. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes-2025, American Diabetes Association, Diabetes Care 2025;48(Suppl 1):S27-S49 (2025)
  6. Staging presymptomatic type 1 diabetes: a scientific statement of JDRF, the Endocrine Society, and the American Diabetes Association, Diabetes Care 2015;38:1964-1974 (2015)
  7. ISPAD Clinical Practice Consensus Guidelines 2024: Screening, Staging, and Strategies to Preserve Beta-Cell Function in Children and Adolescents with Type 1 Diabetes, Hormone Research in Paediatrics 2024;97:529-545 (2024)
  8. Comparison of IA-2 Bridge ELISA and Radiobinding Assays for Progression Risk Assessment in Early-Stage Type 1 Diabetes, Diabetes, Obesity and Metabolism 2026;28:4409-4412 (2026)
  9. The longitudinal loss of islet autoantibody responses from diagnosis of type 1 diabetes occurs progressively over follow-up and is determined by low autoantibody titres, early-onset, and genetic variants, Clinical & Experimental Immunology 2022;210:151-162 (2022)
  10. LOINC codes verified with the NLM Clinical Tables LOINC search (e.g. 56718-0), U.S. National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

Related markers