I just got my blood tests from the blood draw my endocrinologist did last week.
Last May, my c-peptide was 3.0 (BG 87). That August, it was 7.3 (BG 120). This October it was 9.6 (BG 117.1). In February it was 4.6 (BG 63.9). This time it was 2.7 (BG 97.3). There's no reference range for this lab, but my endo says that when they aren't fasting, c-peptides should be between 2 and 4, depending on the corresponding blood sugar.
Before last August, I'd never had a c-peptide above 3. It's interesting to note that that was around the same time I began blood sugar hell, and that the c-peptide of 4.6 was at a time when I was having more trouble with my BG. I assumed it was coming down on its own.
After the appt in February, I began metformin. Does anyone here know if metformin lowers c-peptide? I would assume it does, since the body uses insulin better. I'd be interested to hear if someone has seen a decrease in their c-peptide with metformin.
Also, I'm still waiting on the results of the antibody tests. (Not that I'm expecting them to come back positive, but even my endocrinologist agrees that it would make far more sense for me to be slow-onset type 1.)
Can't help you on the Metformin question. But in general I don't think of c-peptide as a "should be" sort of thing so much as a diagnostic sort of thing.So I think that "2-4" is what is considered normal, defining things as above and below that. If it is low, you are not producing much insulin and this is indicative of Type 1. If it's normal or high it's indicative of Type 2 as Type 2's produce an excess of insulin as they have trouble utilizing it efficiently due to IR. I'm sure others can explain it better. But according to Walsh if insulin is being injected the c-peptide might read low rather than high and that the test is ideally done on blood drawn when the blood sugar is above 180 to drive insulin production as high as possible (Using Insulin page 45)He does say that "if the c-peptide s are in the low normal range the person may have Type 1.5 or Type 2". So that 2.7 leaves you in diagnostic limbo but the other numbers indicate Type 2. I think for clarification of diagnosis the standard is the combination of antibody tests and c-peptide. Why does your endo think it would make far more sense for you to be slow onset type 1?
There were three abnormal tests for c-peptide. Other than that, the 16 or so c-peptides I've had drawn over the last four years have been normal.
I don't have any evidence of metabolic syndrome, and I'm very young for T2. Children can get T2, but they're always, always obese, which I am not.
I got worse about a month after taking Januvia, which stimulates the pancreas to make more insulin. If I were slow-onset T1, this could be explained by my body attacking my beta cells more rapidly due to the increase in insulin production.
I react very badly to all carbs without metformin. At this point, I think if I went off of it, all carbs would put me over 200 for an extended period of time.
I brought up the high c-peptide and T1 issue. I said that if my body were attacking the insulin itself, my body would make more than it would otherwise need. That could raise c-peptide. He said that it's uncommon and it would be a bit more indirect than that, but that since I'm atypical anyway it isn't out of the realm of possibility.
Like I told him, the high c-peptide is the only thing keeping me from insisting I'm slow-onset T1.
