GAD antibodies and C peptide test

AngieGribb said:

Hi - I have recently been diagnosed as type 2, although 2nd Hba1c was just in pre diabetic range. I am planning to get GAD and C peptide tests done as I am skinny and exercise regularly so wonder if I am 1.5 really. GP not interested so will do it privately and was wondering if I should get insulin level done as well? From reading around it looks like c peptide is effectively measuring insulin anyway - would like to keep it as cheap as possible!
Thanks for your help

Angie

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One does not need to be overweight to be a T2. Do you know what the diagnosis was based on?

I can appreciate wanting to confirm your diagnosis so do what you need to do.

However, as @urbanracer mentioned, there are plenty of people with type 2 diabetes who have a normal BMI. Please don't take this the wrong way, but if you were in your 20s-30s it would be a much different story and I'd say the GAD/C-peptide tests should be mandatory, but being in your early 50s lessens the chance (though certainly possible) that you have an autoimmune disease.

To answer your question, I'd say that the most important test at this point is the GAD antibody test. If you are in fact LADA, you may still have c-peptide/insulin levels within "Normal" ranges. Plus, showing any doctor a positive GAD-65 antibody test SHOULD qualify you to get the c-peptide test done afterwards anyways.

As @TorqPenderloin stated, the GAD test is probably a good idea but it's not always conclusive.

With insulin resistance, symptoms often include weight gain, lethargy, hunger, difficulty concentrating and elevated blood pressure. You can read more about IR here........

http://www.diabetes.co.uk/insulin-resistance.html

I can understand that you want a definitive diagnosis but it's not always straightforward for us. I guess it depends how desperately you need to know. It seems like your BG levels are back in the pre-diabetic levels so maybe just monitor your situation closely?

Hi. I've been thru the diagnosis of T2 at age 50 when I was stick thin, having a sensible diet and going to the gym 3 x a week. My private c-peptide showed low insulin but the GAD was negative. My blood sugar was very high and continued until I had to go onto insulin. So, the fact that your blood sugar is still in a fairly good range tells me your insulin output is probably still quite good even though you are thin. I would be inclined to avoid the cost of the two tests at this stage but it's your choice. Yes, I would just do the GAD as I suspect the c-peptide will show good insulin levels. If the GAD is positive then you know where you are heading. If negative then do nothing apart from monitoring you bs every so often and keeping in contact with the GP. Although there are some T2s who are not overweight they would be expected to have insulin resistance from internal deposited fat. I still believe a good proportion of slim T2s are mis-diagnosed T1s and NICE is beginning to recognise this. A lot depends on how you define T2.

Hi. I was diagnosed with diabetes this year and due to my age , mid forties, it was assumed that I had T2. I changed my diet to a low carb diet and my HBa1c went from diabetic to pre diabetic range, I was feeling good but I still had a nagging feeling that I should get tested to make sure it was T 2 so I asked my doctor if I could be tested. I had a GAD test and two weeks later i got a call from a diabetic nurse confirming that I actually had type 1 diabetes and I had to go on insulin immediately, so yes I would say It is definitely worth getting tested.

Do bear in mind that you could also be MODY -- but again GAD and c-peptide aren't definitive. Is there diabetes T1 or 1.5 in your family? (often a useful indicator)

desidiabulum said:

Do bear in mind that you could also be MODY -- but again GAD and c-peptide aren't definitive. Is there diabetes T1 or 1.5 in your family? (often a useful indicator)

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While a c-peptide test is not definitive for MODY and a GAD test is essentially irrelevant if you are looking for MODY (although if it were positive you would be type 1), there is a definitive test for MODY because MODY occurs where there are specific mutations on specific genes - either you have the mutation (and you are MODY) or you don't (so you are not MODY). If you think MODY might be a possibility then you may want to consider asking for genetic testing.

Edit to add apologies to @desidiabulum - sorry, you obviously know this (& I confess I replied without reading your signature because when I read your post without being logged in it did read like there was no definitive test for MODY - I guess I was just concerned that OP reading might not even have heard of MODY or to ask for genetic tests if there is a concern this might be a possibility). Sorry.

catapillar said:

While a c-peptide test is not definitive for MODY and a GAD test is essentially irrelevant if you are looking for MODY (although if it were positive you would be type 1), there is a definitive test for MODY because MODY occurs where there are specific mutations on specific genes - either you have the mutation (and you are MODY) or you don't (so you are not MODY). If you think MODY might be a possibility then you may want to consider asking for genetic testing.

Edit to add apologies to @desidiabulum - sorry, you obviously know this (& I confess I replied without reading your signature because when I read your post without being logged in it did read like there was no definitive test for MODY - I guess I was just concerned that OP reading might not even have heard of MODY or to ask for genetic tests if there is a concern this might be a possibility). Sorry.

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Hi -- no need to apologise, and I quite take your points. I wouldn't want to suggest that there isn't a test that can definitively identify MODY - it's more that there isn't necessarily a test that can definitely discount it. MODY occurs where there are specific mutations on specific genes, as you rightly say, but they are discovering new gene mutation variants all the time, and people like me have simply been told that they are MODY but with unidentified gene. I'm sure there are a number of us who have basically given up on ever getting a 100% certain diagnosis of why our pancreas isn't working properly -- the key is just finding out through trial and error what can keep our BGs stable

Did you find out any more?