I’m not sure if I’m experiencing a “second honeymoon” after nearly 60 years and I’m wondering about something.
Many years ago I was told that the C-Peptide test was used to determine which type of diabetes you had (and maybe even if you have it - I’m not sure): the physician said that the amount of insulin you produce is matched by an equivalent amount of C-Peptide, which could be measured. So I’m wondering especially for those of us who have been at this for a while - has anyone had a C-Peptide test done to confirm? Or any other test for that matter? I would like to think there was a way to know for sure (yeah, right😊!)
Hi Dorie. C-peptide, is a short 31-amino-acid polypeptide that connects insulin’s A-chain to its B-chain in the proinsulin molecule. It is identifiable and it is left over when your own insulin is produced. You can test for it. The presence of c-peptide only means you are making your own insulin. You may have very little c-peptide if for example you are on a strict carb-free diet. It doesn’t mean you are type-1. Doctors use it along with blood sugar for preliminary analysis: high blood sugar and high c-peptide is evidence of type 2. High blood sugar and low c-peptide is evidence of type 1 or some other endocrine problem preventing you from making insulin. Normal blood sugar and low c-peptide is inconclusive. There isn’t an absolute yes-or-no test for type 1 diabetes. So sometimes it’s a matter of when there is enough evidence to make a therapeutic call, such as starting a patient on insulin or starting them on metformin. 
medicine isn’t usually exact.
Also, @wadawabbit every couple years I start making insulin again and it lasts a few days to a few weeks and then it goes back to regular crazy. Good luck 
Thank you for both your posts - I appreciate it when people can put technical info into a new easily understandable form.
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You’re welcome Dorie. A final thought, if you are taking insulin, your body doesn’t need any and so your c-peptide (if already taking insulin and you can make a little insulin) should be very low. Last time I was making insulin I enjoyed some pasta and some other harder to eat foods. Careful for lows!
Yeah. I’m trying to figure out what’s going on and the thought of my pancreas reminding me “I’m here! I’m here!” crossed my mind. Then again I may need to adjust some pump settings. Oh sweet mystery of diabetes life!
Dorie @wadawabbit , I concur with what Joe wrote, and just add that c-Peptide is one of the tools used to accurately diagnose diabetes and is one of the keys that separates autoimmune diabetes T1D from other types.
You ask if any long-termer have recently had c-Peptide - YES, in the last ten years I’ve had two of those blood tests but not for diagnosis purposes. Medicare has required c-Peptide for each new pump prescribed for me. Both test results for me were <0.01% meaning that no c-Peptide could be found.
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Wow! that’s really intriguing. how do you know you are producing insulin again?
do you take any tests?
Hi @Matt1 finger sticks. The last time it happened I started having severe lows after meals, without warning, I realized I had to correct the same amount of carbs I bolused for. So if I gave myself 5 units for lunch I would go low at 1:30 and I would need to correct over 60 grams of carbs to get my blood sugar above 70. So for the next meal I didn’t bolus at all and had normal blood sugars. And by normal I mean 70-75. No spike. As a hype 1 if I can eat a meal and stay 70-75 without additional insulin, it can only mean 1 thing - I’m making my own insulin. I left my basal the same figuring I would need that for when it stopped. I asked my doctor brother if I might have a insulin tumor he said it was extremely rare and I’d be low all the time. Anyway. Lasted a week. Then I needed insulin again.
Matt @Matt1 , good to see you again - just recently I began wondering how your son was getting along with managing his diabetes.
My experience with my body resuming production produces symptoms much like @Joe and I process these events much like he said. For me, the “worst” part is trying to get my levels back into the 80s where I feel comfortable. Another thing is, when my body returns to “being normal T1D” is that I hesitate to increase my insulin right away to the level it should be and, as a result, often have BGL above my comfort zone for a while.
This is really super intriguing. there was some research about it, but i was not aware it was actually observable in that way. it would be really interesting to know the c-peptide levels you both had, so we could exclude shifts in insulin resistance (e.g. following strenuous exercises) as causes.
did you notice any particular circumstances in which such condition (lows) occurs?
Matt @Matt1 , I just do it “the old fashioned way”, by observance and verifying how my body is feeling by watching my CGM readings. Yes, I will double check with finger-stick to make sure that my continuous sensor is not just reading low. But mostly, my diagnosis is is being aware of how I feel. I never took the bother to request ordering a c-Peptide lab, having blood drawn and waiting another day for results.
As far as confusing a TEMPORARY reactivation of my β cells with lessening of insulin resistance, because reactivation of β cells is usually of short duration, I assume the former. If your son is loosing his resistance to insulin, he will continuously need less insulin to do the work it used to do and stay less for a longer while.
@Dennis I think you are confusing me with a different user - I dont have a son. different matt?