Can someone help me understand the c peptide test? I found out the result of mine was 4.5. What does that mean? I was diagnosed type 1 in December in DKA and a BG of 550. This is the first time I've had bloodwork done since diagnoses (test was done exactly 2 months after diagnosis). Right now I'm honeymooning, so I'm still making some of my own insulin but I'm using lantus as well. BG are good fasting and before meals 80s & 90s. 2 hour post meals are high 100's to 220ish. My endo thinks i'm definetly going to add some novolog to the mix as well.


But anyway, I'm really confused as to what the c peptide test measures. What are the ranges for guidelines and things like that? What do the results mean?


I had the test done fasting (8:00 am) if that helps anything


By the way in only 2 months after diagnosis I dropped my a1c from 14.8 to 7.6! So that is definetly some inspiring news!

Tags: 1, 2, a1c, blood, bloodwork, c, cpeptide, diabetes, fasting, glucose, More…insulin, meals, peptide, pump, test, type, work

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The c Peptide reference range for normal on my lab sheet says 1.0-5.0. You must be very early in your diagnosis.
Yes, this means that you are still honeymooning! Your natural insulin production will likely decrease over time (though it's hard to predict at what rate). Just don't be surprised if you start needing significantly more insulin than you do now. My amount of injected insulin doubled when my honeymoon was over. As I remember, my honeymoon ended quite suddenly and one day I woke up with a blood sugar over 400 and new it was time to increase the insulin doses.

Congrats on the A1c!! Does your doctor want you to add Novolog for high carb meals? It might not be a bad idea to prevent you from going high after meals. You should definitely not go above 180 after meals, though even better if you can avoid going over 140 (I won't tell you to do that because I am still not able to -- though that's my goal!!). A small dose of Novolog only with high carb meals might improve your blood sugars a lot!
There are two measurement units for c-peptide, ng/mL and nmol/L. Since you are in the US, you probably were given a c-peptide in the ng/mL units. Different labs will quote different normal ranges, Labcorp quotes me 1.1-4.4 ng/mL as the reference range. Interpreting the c-peptide really depends on your blood sugar at the time of a test. If you had even a mildly elevated sugar and without any other knowledge, you would probably be diagnosed as a type 2. In either case, the result of the test shows that you still have some significant insulin production. That is a good thing. If you tested with a low c-peptide with a markedly elevated blood sugar, then you would be considered insulin deficient.
Does having external insulin in the body effect the results? I mean, if I took my normal dose of lantus the night before, would that skew the findings of the test?
According to my pump trainer, no, it wouldn't skew it. I asked her last week as I wanted to get the test done again.

My labs range for C Peptide is 0.8-3.1, I was 0.5 05/23/2008. At the time I was still being treated as a type 2 on oral meds only, no insulin.
Carrie's pump trainer is correct. Exogenous insulin dosed does not correspond to any C-Peptide because it is made in a lab and there is no connecting peptide to proinsulin in vials of insulin purchased from a pharmacy because it is 100% synthetic, which means using insulin will have absolutely no impact on your C-Peptide results. The test measures endogenous insulin production only.
ummmmm, actually exogenous insulin can cause a suppression of natural insulin production and can have an effect on c-peptide.
Provided, of course, that there is endogenous insulin production to begin with, but at the trace amounts he reports, there is not much to suppress.
But Scott, he has reported that he is producing c-peptide at the upper end of the reference range. He is in that honeymoon stage. So in Tim's case, he actually might have even higher insulin production capability than shown in his test.
The reference ranges vary from one lab to the next, but if one uses Medicare's criteria for coverage of an insulin pump, the amount should be a fasting C-peptide level that is less than or equal to 110 percent of the lower limit of normal of the laboratory’s measurement method. He reported the lab result, but unless I'm mistaken, the lab's range was not provided.
Yes, but Tim indicated his c-peptide was 4.5 ng/mL far above that the lower limit of basically all the labs. I think we are confused about what we are talking about.
There seems to be contradictory information. Type 1 diabetics cannot produce insulin at all and therefore little or no C-peptide which is related to insulin production. C-peptide values for type 1 diabetics are generally very low, way under 5. C-peptide values around 5 and up are typical of type 2 diabetes. That's why I spoke of contradictory information.




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