Glutamic Acid Decarboxylase

Metabolic Health

A healthy result should fall into the range 0 - 0.5 nmol/L.

Glutamic acid decarboxylase is an enzyme found in brain and pancreas that converts glutamic acid (glutamate) into GABA, an inhibitory neurotransmitter. The glutamic acid decarboxylase test is a test that looks for antibodies directed against the glutamic acid decarboxylase enzyme. While glutamic acid decarboxylase is a critical enzyme in brain, it is also found in beta cells in the pancreas. Some individuals develop autoantibodies against glutamic acid decarboxylase. When these antibodies are detectable in the blood, they may represent an autoimmune disease. The test is performed using radioimmunoassay. The absence or very low levels of glutamic acid decarboxylase autoantibodies are considered normal. Less than 10% of healthy individuals will have low levels of glutamic acid decarboxylase antibodies, suggesting that they may be present in people without disease.

Normal Ranges for Glutamic Acid Decarboxylase:

Less than or equal to 0.02 nmol/L



Glutamic Acid Decarboxylase result calculator

insert the value from you Glutamic Acid Decarboxylase test result.

What does it mean if your Glutamic Acid Decarboxylase result is too low?

It is not possible to have glutamic acid decarboxylase antibody levels that are too low.

What does it mean if your Glutamic Acid Decarboxylase result is too high?

The two main types of diseases in which glutamic acid decarboxylase autoantibodies are present are diabetes and neurological disease. Approximately 4 out of 5 people with type I diabetes will have low levels of these autoantibodies. On the other hand, less than 5% of people with type II diabetes will have detectable amounts of these autoantibodies in their serum. The presence of these autoantibodies does not necessarily diagnose particular neurological diseases; however, a portion of people with various autoimmune neurological disorders will have low titers of glutamic acid decarboxylase antibodies. These antibodies may also predict a predisposition to certain autoimmune diseases such as autoimmune thyroid disease, pernicious anemia, Addison disease, and vitiligo. 

Some specific causes of glutamic acid decarboxylase antibodies are:

  • Type 1 diabetes
  • Type 2 diabetes
  • Myasthenia gravis
  • Lambert Eaton syndrome 
  • Stiff person syndrome
  • Autoimmune encephalitis
  • Brainstem encephalitis

Upload Full Test and Learn More

To learn more, visualize and track your test results, create a personal account.

Sign Up, Upload Tests, Get Insights and Improve with

Sign up now.

Are you concerned about your blood test results?
Then get your personal health dashboard.


Personal Plan +

Unlimited Tests Upload Subscription
Cancel anytime

Sign Up


Personal Plan Basic

Single test upload.
Pay for each test result upload.

Upload Now

Your Privacy And Security

At HealthMatters, we're committed to maintaining the security and confidentiality of your personal information. We've put security measures in place to help protect against the loss, misuse or alteration of information under our control. We use procedural, physical and electronic security methods designed to prevent people who aren't authorized from getting access to this information. Our internal code of conduct adds additional privacy protection. See our Privacy Policy for more information.