GAD antibodies or Glutamic Acid Decarboxylase (GAD65) Test: Purpose, Normal Range and Findings

Glutamic Acid Decarboxylase Antibodies test is used to determine whether the patient has Type 1 diabetes, Type 2 diabetes or Latent Autoimmune diabetes of adulthood.

Updated: June 16, 2022


Glutamic Acid Decarboxylase Antibodies test is used to determine whether the patient has Type 1 diabetes, Type 2 diabetes or Latent Autoimmune diabetes of adulthood. Glutamic acid decarboxylase (GAD) is an enzyme required for the pancreas to function normally. Antibodies that target this enzyme are called GAD antibodies. An antibody is a protein that your immune system uses to attack foreign objects, which are often potentially harmful, such as viruses or bacteria.
Sometimes, the immune system makes antibodies that mistakenly attack normal cells that aren't  harmful causing autoimmune disorder. GAD antibodies are found in the blood of most of the people with type 1 diabetes.This test is particularly done for the patients above the age of 30 who suffer from diabetes.

Purpose of GAD65 Test:

GAD antibody testing is primarily used to differentiate between type 1 diabetes from diabetes due to some causes. The test is done when a person is newly diagnosed with diabetes to know the type of diabetes in the body. Type 1 diabetes is due to lack of insulin where as type 2 diabetes develops due to insulin resistance. When a person is diagnosed as Type 2 but have a great difficulty in controlling his/her glucose levels with standard treatments, this test will be helpful.
Instead of a specific GAD test, you can also have an antibody panel test which include GAD and other antibodies. Other antibodies associated with type 1 diabetes include:

  • islet cell cytoplasmic autoantibodies (ICAs)
  • insulinoma-associated-2 autoantibodies (IA-2As)
  • insulin autoantibodies (IAAs), which are more common in children than adults

This test also determines whether gestational diabetes is type 1 diabetes or not. Along with type 1 diabetes mellitus detection, this test is also helpful in finding related endocrine disorders such as thyroiditis and pernicious anemia.
All of these tests are done by a simple blood test. You won't need to fast or do anything else to prepare. A healthcare professional will take blood from a vein in your arm and send it to a laboratory for analysis. The results usually arrive after 2-3 days. After taking the sample the area from where blood was taken out is bandaged by the health professional.You most likely have type 1 diabetes if GAD or any of these other antibodies are found. If no GAD antibodies are found, you probably have type 2.

Normal Range and Findings:

The normal value for GAD antibodies testing is less then or equal to 0.02 nmol/L. Greater then 0.02 nmol/L are found in classic stiff-man syndrome and in related autoimmune neurologic disorders such as acquired cerebellar ataxia, some acquired nonparaneoplastic encephalomyelopathies.
Diabetic patients with polyendocrine disorders also generally have glutamic acid decarboxylase (GAD65) antibody values greater then 0.02 nmol/L. patients who have type 1 diabetes without a polyendocrine or autoimmune neurologic syndrome will have usually less then 0.02 nmol/L.
Low titers which is between 0.03 to 19.9 nmol/L are detectable in the serum of most of type 1 diabetic patients. Patients with myasthenia gravis, Lambert-Eaton syndrome, and rarer autoimmune neurological disorders will also have low titers.

Causes of high GAD antibody levels:

Type 1 diabetes is not the only reason someone might have high GAD antibodies. They are also linked to other conditions, which include:

  • stiff person syndrome, which is a neurological condition that causes stiff muscles and muscle spasms
  • cerebellar ataxia, which is a brain disorder that causes sudden, uncoordinated muscle movement
  • other autoimmune diseases, including rheumatoid arthritis and thyroid disease

If you are diagnosed with diabetes and GAD antibodies are found in the serum, it is likely that you have type 1 diabetes.


Related Articles

Absolute Lymphocyte Count Test: Purpose, Preparation, Procedure and Result

Absolute Lymphocyte Count Test: Purpose, Preparation, Procedure and Result

The absolute Lymphocyte Count test is performed to measure the level of Absolute Lymphocyte Count in the blood.

Osteoporosis and Its Causes

Osteoporosis and Its Causes

Osteoporosis means porous bone. It is a disease characterized by low bone mass and loss of bone tissue that may lead to weak and fragile bones.

Psoriasis: Symptoms, Types, Causes, Triggers, Risk Factors, Diagnosis and Complications

Psoriasis: Symptoms, Types, Causes, Triggers, Risk Factors, Diagnosis and Complications

Psoriasis is a chronic, inflammatory skin disease which is related to inherited genes. It causes cells to build up rapidly on the surface of the skin.

Asthma Diagnosis, Classification and Its Complications

Asthma Diagnosis, Classification and Its Complications

Diagnosis of asthma can be done by taking a thorough medical history and performing breathing tests to measure how well your lungs work.

Why does a child have epilepsy and What is a childhood epilepsy syndrome?

Why does a child have epilepsy and What is a childhood epilepsy syndrome?

Children develop epilepsy as a result of brain injury which could be due to severe head injury, difficulties at birth, or an infection which affects the brain such as meningitis. Epilepsy with a known cause like this is called symptomatic e

Asthma: Causes, Symptoms and Risk Factors

Asthma: Causes, Symptoms and Risk Factors

Asthma is a long-term inflammatory disease of the airways of the lungs. The problem in the bronchial tubes that carry air into your lungs can make it hard for you to breathe. These airways get so narrow that air can not move freely causing

8 Home Remedies for Sunburn

8 Home Remedies for Sunburn

Sunburn is the most evident sign that you've been sitting outside for a really long time. Yet, sun harm isn't generally obvious. Under the surface, bright light can change your DNA, rashly maturing your skin.

T3 Test: Purpose, Preparation, Procedure and Results

T3 Test: Purpose, Preparation, Procedure and Results

Most of the T3 in your body binds to protein. Free T3 are the T3 that are not bind to protein and circulates in your blood. T3 total test is done to measures both kinds of T3 in your blood.

Suppliers Across World


Browse suppliers across the globe including Norfolk Island, Portugal, South Korea, Cuba, Martinique, Montserrat, Kiribati, Bouvet Island, Cambodia, Bulgaria, Togo, Germany, Bolivia, Brazil, San Marino, Belgium, Benin, Syria, French Southern territories, Colombia, Cocos (Keeling) Islands, Chad, Barbados, Romania, Croatia, Turks and Caicos Islands, Spain, Austria, Guam, Tunisia, Norway, Philippines, Australia, Burkina Faso, Paraguay, Sierra Leone, Mexico, Uruguay, Palestine, Sudan, Namibia, Comoros, Honduras, Sao Tome and Principe, Saint Lucia, Marshall Islands, Scotland, Swaziland, Mauritania, Myanmar and other localities of World as well..