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Glutamic Acid Decarboxylase 65 Antibodies (GAD65-Ab)

Published: July 27, 2026Updated: August 25, 2026

GAD65-Ab measures antibodies against the enzyme glutamic acid decarboxylase 65, which is crucial for the synthesis of the neurotransmitter GABA.

Quick summary

GAD65-Ab is a diagnostic biomarker for autoimmune diabetes and neurological disorders.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
IU/mL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Roche GAD Ab, Abbott GAD Ab, RSR GAD65 Ab
interpretation: {"text":"0–5 IU/mL: No significant GAD65 antibodies detected.","label":"Normal"}; {"text":">5 IU/mL: Presence of GAD65 antibodies, suggestive of an autoimmune response.","label":"Elevated"}

Glutamic acid decarboxylase 65 (GAD65) is an enzyme found in pancreatic beta cells and neurons, responsible for the synthesis of gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter in the central nervous system.

The presence of GAD65 antibodies (GAD65-Ab) in the blood indicates an autoimmune response, often associated with Type 1 diabetes and other autoimmune conditions such as stiff-person syndrome and cerebellar ataxia.

Measuring GAD65-Ab levels is essential for the early diagnosis and differentiation of these conditions, as well as for predicting the risk of developing autoimmune diabetes.

Frequently asked questions

What is the normal range for GAD65-Ab?
The normal range for GAD65-Ab is typically 0–5 IU/mL.
What conditions are associated with elevated GAD65-Ab levels?
Elevated GAD65-Ab levels are associated with Type 1 diabetes, stiff-person syndrome, and cerebellar ataxia.
  1. 1
    National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)Source
  2. 2
    American Diabetes Association (ADA)Source

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

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Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy