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Glutamic Acid Decarboxylase (GAD65) Antibody, Serum

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

This test measures the presence of antibodies against the GAD65 protein, which is linked to certain autoimmune conditions affecting the nervous system.

Quick summary

["This test helps diagnose or monitor type 1 diabetes and other autoimmune disorders like stiff-person syndrome or cerebellar ataxia."]

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

Key facts at a glance

LOINC
101233-5
Short code
GAD65 Ab Ser Ql IB
Synonyms
GAD65 Ab Ser Ql IB
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
ib
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order this test if you have symptoms of type 1 diabetes, such as frequent urination, extreme thirst, unexplained weight loss, or fatigue. It may also be used in people with other autoimmune neurological conditions or unexplained muscle stiffness.

What to Expect Before the Test

No special preparation is needed. You may have a small needle inserted into your arm to draw blood. If you’re on blood thinners, let your doctor know before the test.

What the Test Results Mean

Positive results suggest an autoimmune response targeting GAD65, which can indicate conditions like type 1 diabetes or other related disorders. Results are not always definitive on their own and may be combined with other tests.

Common Conditions Linked to This Test

Elevated levels are often seen in type 1 diabetes, but they can also appear in other autoimmune conditions affecting the nervous system, such as stiff-person syndrome or cerebellar ataxia. Your doctor will interpret results in the context of your symptoms and other tests.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

GAD65 Antibody (Serum)

Frequently asked questions

What does a high level of GAD65 antibodies mean?
High levels may indicate an autoimmune attack on the pancreas or nervous system, supporting a diagnosis of type 1 diabetes or related disorders. However, not everyone with these antibodies will develop symptoms, so results should be reviewed by a healthcare provider.
Can this test be used to diagnose type 1 diabetes alone?
No, this test is often used alongside other markers like C-peptide or glucose levels to help diagnose type 1 diabetes. It helps confirm an autoimmune process but isn’t a standalone test.
How often should I get this test if I have diabetes?
Your doctor may recommend monitoring GAD65 antibodies periodically if you have type 1 diabetes or related conditions, especially if symptoms change or if you’re being treated for an autoimmune disorder.
  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