Ordering Recommendation

Most useful to establish autoimmune etiology in previously diagnosed type 1 diabetes mellitus (DM). Do not use to differentiate type 1 DM from type 2 DM, for most cases.
If pursuing antibody testing to determine autoimmune DM, perform at least two antibody tests. In most cases, use glutamic acid decarboxylase antibody in combination with another antibody test. Other antibody tests include Islet Antigen-2 (IA-2) Autoantibody (3001499), Insulin Antibody (0099228), Islet Cell Cytoplasmic Antibody, IgG (0050138), and Zinc Transporter 8 Antibody (2006196). For analysis in CSF, refer to Glutamic Acid Decarboxylase Antibody, CSF (3002788).

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation

Serum separator tube.

Specimen Preparation

Transfer 1 mL serum to an ARUP Standard Transport Tube. (Min: 0.5 mL)

Storage/Transport Temperature


Unacceptable Conditions

Plasma. Grossly hemolyzed specimens.


Ambient: 24 hours; Refrigerated: 1 week; Frozen: 3 months


Semi-quantitative Enzyme-Linked Immunosorbent Assay




1-3 days

Reference Interval

0.0-5.0 IU/mL

Interpretive Data

A value greater than 5.0 IU/mL is considered positive for glutamic acid decarboxylase antibody (GAD Ab).

This assay is intended for the semi-quantitative determination of the GAD Ab in human serum. Results should be interpreted within the context of clinical symptoms.

Compliance Category



Hotline History


CPT Codes



Component Test Code* Component Chart Name LOINC
2001772 Glutamic Acid Decarboxylase Antibody 56540-8
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


  • 64K Antibody
  • Anti-GAD Antibodies
  • Anti-Glutamic Acid Decarboxylase Ab
  • Beta Cell Antibody
  • Beta-Cell Autoantibody to GAD 65
  • GAD Antibody
  • GAD-65
  • GAD65
  • GAD65 Antibody Assay
  • Glutamate Decarboxylase Antibodies
  • Pancreatic Islet Cell Ab
Glutamic Acid Decarboxylase Antibody