C-Peptide

[gettingby]

Is it unusual that I have been a T1 for almost 25 years and have never had a C-Peptide done? Are there any other long timers out there who haven't? I see others posting their C-Peptide results and wonder if it is necessary for me at this point.

Thanks.:)

[strack350]

to tell the truth I don't think I've ever had one either, not within the past 10-15 years anyways. I also have had type 1 for 25 years. unless the doc does it with my yearly cholesterol/blood tests. I get an a1c every 3 months though.

[Subby]

Never had one. I guess a reason for getting a c-pep at this stage down the track, might be if you get a lot of variation in overall insulin requirements, it seems on a weekly or semi weekly or monthly, kind of basis. That's what the 1.5s tend to report. In our circumstance, not sure the knowledge does a great deal except give a potential explanation for variability.

Otherwise, I'm thinking there's not much point for those of us obviously insulin bound, except for curiosity as to whether there is anything there at all or not. Which I am idly considering, myself...

[poodlebone]

I didn't have one until 4 years ago, after 18 years with T1. I started seeing a new (my current) CDE and she ordered both c-peptide and GAD antibodies tests. At the time (4+ years ago) I still had no clue what the results really meant. She told me at the time it means that I made absolutely no insulin and have million of antibodies.

I saw her for a regular appointment today and finally looked at my results from 4 years ago. They were:
c-peptide: <.5
GAD: 2987 (or 2897, I may have mixed up two digits)

Don't know what the lab reference ranges were.

[sarahspins]

I had a few done early on, when it wasn't clear just what my diagnosis was (I was diagnosed @ 20). Initially my c-peptide levels were in the "normal" range.. but on the lower end (1.7, 1.2, non-fasting). Eventually, I dropped out of normal (interestingly enough this coincided with when I finally got antibody testing done, which cleared up the "confusion"), and the last one I had done back in early 2003 (again, non-fasting) was 0.3.

It's useful only in determining how much insulin you are making on your own.. which after nearly 25 years with T1 is likely to be almost non-existant. If you were still honeymooning however, it could be useful to see how much insulin is being made.

There are other occations such as securing pump coverage with medicaid/medicare where they require a c-peptide level of 0.5 to confirm a T1 diagnosis.. even if you've already lived a lifetime of T1.

[UpNorth]

I had it done a couple of times within the first 2 years with diabetes. Last time it was done, about 3 years ago, my doctor got pretty shocked to see i had no insulin production whatsoever in my body, so relatively soon after being diagnosed:confused: Antibodies were sky high too :T
Since then they haven't bothered to test it again :D

[WhyNotSmile?]

My C-peptide was normal at the time of diagnosis. And insulin level was decreased to half of normal range :confused:

[Subby]

Whynot, I'm just thinking that pretty much any idea of "normal" in that sentence - normal c-peptide, normal range of injected insulin, have a huge range between different people.

[GretchO]

i've never had one either, don't know if it would be useful for me at this point. i'm pretty certain i'm making very little or no insulin.

[WhyNotSmile?]

it is questionable would level of c-peptide be accurate because you are under insulin therapy, so if there is enough "external" insulin there is no need for c-peptide production. It will be low, I guess

[WhyNotSmile?]

Whynot, I'm just thinking that pretty much any idea of "normal" in that sentence - normal c-peptide, normal range of injected insulin, have a huge range between different people.

well if you assume that normal range of insulin is average range in huge, huge number of people and your result is decreased comparing to that normal range, you can conclude that level of c-peptide should fit in that. C-peptide determine how much insulin you produce, but there are unanswered questions still, obviously

[acstokes]

My understanding is that normal is in the 3-4 range. Mine was 3 one year ago, but was at 1.3 one month ago. That's when my doc said I had gone from a Type 2 to a Type 1.5.

[NoraWI]

Reduced insulin production does not make you go from Type 2 to Type 1.5. It is the cause of your diabetes that determines your type. If your cause is autoimmunity, then you are a T1. If the cause is autoimmunity with slow onset later in life, then you are Type 1.5. If the cause is Insulin Resistance (IR), then you are a Type 2 no matter how much or how little insulin you produce. Some doctors don't seem to understand that.