What the test measures
GAD65 stands for glutamic acid decarboxylase, an enzyme found in the insulin-producing beta cells of the pancreas. In autoimmune diabetes, the immune system mistakenly produces antibodies against GAD65. The test measures how many of these antibodies are in your blood.
It’s a single blood draw, no fasting required, and results typically come back within a few days to two weeks depending on the lab.
Reading your result
Labs report GAD65 antibody levels as a number (in units per milliliter), compared against a threshold set by that specific lab. Anything below the threshold is reported as negative; anything at or above it is positive. The exact cutoff varies by lab, so compare your number against the reference range printed on your own report rather than a number you saw elsewhere.
A higher antibody level doesn’t necessarily mean faster disease progression. It confirms that the autoimmune process is present, not how far along it is.
What a positive result means
A positive GAD65 result means your immune system is actively producing antibodies against your pancreas’s insulin-producing cells. In the context of an adult diabetes diagnosis, this is the primary lab marker used to identify LADA rather than Type 2.
On its own, a positive result doesn’t tell you how much insulin-producing capacity you have left, that’s what a C-peptide test is for. The two tests are usually read together: GAD65 confirms the autoimmune cause, C-peptide tracks how much function remains.
Related tests
- C-peptide measures how much insulin your pancreas is still producing.
- ICA (islet cell antibodies) and IA-2 antibodies are additional autoimmune markers sometimes tested alongside GAD65, particularly if the GAD65 result is borderline.
Where to go from here
If you don’t already have a diabetes diagnosis and are reading this out of general concern, this test is ordered by a doctor and isn’t something to interpret alone. If you have a result in hand, LADA vs. Type 2 Diabetes walks through what the fuller picture looks like.
This page is educational, not medical advice. Your own doctor can interpret your result in the context of your full history.