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Glutamic Acid Decarboxylase Antibodies (Anti-GAD65) in Serum

Published: August 9, 2026Updated: August 16, 2026

This test measures the presence of antibodies against glutamic acid decarboxylase 65 (GAD65), a protein involved in insulin production. It is often used to help diagnose type 1 diabetes or other autoimmune conditions affecting the pancreas.

Quick summary

["Helps identify autoimmune conditions affecting insulin production."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
94711-9
Short code
GAD65 Ab CSF IA-sCnc
Synonyms
GAD65 Ab CSF IA-sCnc
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ia
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

What Is This Test Measuring?

GAD65 is an enzyme critical for producing the neurotransmitter gamma-aminobutyric acid (GABA) and the hormone insulin. In autoimmune diseases like type 1 diabetes, the immune system mistakenly attacks GAD65, which can disrupt insulin function. This test detects antibodies that target this protein, indicating an immune response against it.

Why Might This Test Be Ordered?

Your healthcare provider may order this test if you have symptoms of type 1 diabetes (such as frequent urination, extreme thirst, unexplained weight loss, or fatigue) or if you have other autoimmune conditions linked to GAD65 antibodies, like stiff-person syndrome or autoimmune pancreatitis.

How Is the Sample Collected?

A blood sample is drawn from a vein in your arm by a healthcare professional. You may feel a small pinch when the needle is inserted, but the procedure is quick and usually not painful afterward.

What Are Common Results?

Results are qualitative (positive or negative) rather than numeric. A positive result suggests the presence of GAD65 antibodies, which may support a diagnosis of an autoimmune condition affecting insulin production.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Autoimmune Disorders and Diabetes Risk

Short name

Anti-GAD65 Antibody

Frequently asked questions

What Does a Positive Result Mean?
A positive result indicates that your immune system is attacking GAD65, which is strongly linked to type 1 diabetes and other autoimmune disorders. This test can help confirm a diagnosis or guide treatment decisions, especially in cases where symptoms are unclear.
What If My Results Are Negative?
A negative result means no detectable GAD65 antibodies were found in your sample. However, this does not rule out type 1 diabetes or other autoimmune conditions. Other tests or further evaluation may still be needed to assess your health.
How Often Should I Get This Test?
The frequency depends on your symptoms and healthcare provider’s recommendations. If you have an autoimmune condition, your provider may monitor this test periodically to track changes in your condition.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy