C-Peptide Error?

[MissyLA33]

Afternoon,

I’m hoping someone with a little more knowledge may be able to assist.

A bit of background - Gestational diabetes with 3 pregnancies between ages 17-21. Diagnosed type 2 at 28, 8 years ago. Managed diet alone for a few years then Metformin for a few more until a very sudden large decline last year (HBa1c from 40-110). Placed on Novorapid and Semglee 6 weeks ago. My Mum was type 2 but re-diagnosed as 1.5 LADA.

I had a C-Peptide test 8 weeks ago when initially referred to diabetic clinic from GP. They felt I could also be a type 1.5 due to symptoms. I’ve just got the results back today which has firmly put me in the Type 2 category - 2,200pmol (2.2nmol) Whoever administrated the test has marked it as a fasting test so as far as the clinic are concerned I’m a type 2 and that’s that. However I was never asked to fast for the test as I didn’t know I was having it before arriving for my appointment. The test was done after a particularly unusual carby breakfast, I usually eat very low carb. This is backed up by the blood sugar test drawn at the same time that came back at 25.8 (astronomical, even for me!). A quick google suggests that post meal C-Peptide normal ranges are significantly higher and actually my result could be on the low side. Can anyone confirm?

Would you request a repeat test in my situation? I’m due a second appointment at the clinic shortly, although no letter as yet. I’m worried that they will refuse and can’t afford a private test currently. I’m just a bit disappointed after asking for one for so long for it to not actually be informative.

Thanks!

 

[ert]

Afternoon,

I’m hoping someone with a little more knowledge may be able to assist.

A bit of background - Gestational diabetes with 3 pregnancies between ages 17-21. Diagnosed type 2 at 28, 8 years ago. Managed diet alone for a few years then Metformin for a few more until a very sudden large decline last year (HBa1c from 40-110). Placed on Novorapid and Semglee 6 weeks ago. My Mum was type 2 but re-diagnosed as 1.5 LADA.

I had a C-Peptide test 8 weeks ago when initially referred to diabetic clinic from GP. They felt I could also be a type 1.5 due to symptoms. I’ve just got the results back today which has firmly put me in the Type 2 category - 2,200pmol (2.2nmol) Whoever administrated the test has marked it as a fasting test so as far as the clinic are concerned I’m a type 2 and that’s that. However I was never asked to fast for the test as I didn’t know I was having it before arriving for my appointment. The test was done after a particularly unusual carby breakfast, I usually eat very low carb. This is backed up by the blood sugar test drawn at the same time that came back at 25.8 (astronomical, even for me!). A quick google suggests that post meal C-Peptide normal ranges are significantly higher and actually my result could be on the low side. Can anyone confirm?

Would you request a repeat test in my situation? I’m due a second appointment at the clinic shortly, although no letter as yet. I’m worried that they will refuse and can’t afford a private test currently. I’m just a bit disappointed after asking for one for so long for it to not actually be informative.

Thanks!

You need to speak to your Diabetes clinic. Your insulin is still high for a non-fasting c-peptide. It should be less the 200 pmol/l for a type 1 clear diagnosis and less than 600 pmol/l for someone who is struggling with their insulin interpreted with your blood glucose. (2,200 pmol/l is your result with high blood sugar you need to ask if it would support insulin resistance and type 2.) Of course, we can't diagnose you on this forum and these are questions to ask your clinic.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5226330/

 

[MissyLA33]

Thank you for your reply Ert.

I will be talking this through with the clinic when I hopefully get an appointment in a few weeks. I would like to go in armed with as much information as possible. At the moment I feel that having such high blood sugar at the time of the test makes it unreliable and I’d rather have a ‘clean’ test even if the end result is the same.

Insulin resistance is very likely. I started on 12 units of Semglee, a 1-15 carb ratio and the standard 2.8 correction value 6 weeks ago. I’m already up to 30 units, 1-5 carb ratio and 1.4 correction and I’m still not getting results in the target range, mainly staying between 11-14. Very frustrating, I naively thought I’d be down to normal range within a couple of weeks.

 

[Daibell]

Hi. I suspect doing the test again with fasting might reduce the number a bit. Do you have excess weight i.e. do you think you have some insulin resistance and hence more likely to be T2.

 

[MissyLA33]

Hi. I suspect doing the test again with fasting might reduce the number a bit. Do you have excess weight i.e. do you think you have some insulin resistance and hence more likely to be T2.

Honestly, yes. I think it’s becoming obvious that there’s insulin resistance. I’m increasing my basal by 2 every couple of days at the moment and it’s making very little difference to my numbers. I do also have weight issues, I’ve been overweight since a child and weight issues run on both sides of my family so those definitely point towards type 2.

Until August last year I was fully in control with perfect numbers, only taking 1 Metformin per day and doing a very low carb diet, consistently had Hba1c’s of 35ish. For some reason in August everything changed and almost overnight. Within a few weeks my numbers were consistently 16-20 no matter what I did. I thought maybe I had become lax on my diet so I tightened everything back up. Over the next few months I went keto, then carnivore in a desperate attempt to gain control but absolutely nothing worked, my hba1c’s consistently came back at 100 or more. Myself and my diabetic nurse were stumped, I increased my metformin every month, no response. So insulin was the only thing I could do. I’ve definitely noticed that even the smalles slip up in diet causes massive swings (from 10-20) My Mum experienced exactly the same thing, I’m pretty much a carbon copy and she was a LADA 1.5

I’m just frustrated at the moment, it doesn’t make a huge amount of difference what type I am but I know I would benefit from CGM because my numbers are so erratic and I have very pronounced dawn phenomenon. I know it’s going to be a fight to get that as a type 2 vs a type 1

 

[Sammy2011]

Didn’t they do a antibody test?

 

[searley]

i would discuss it with your clinic... as far as im aware if you eat then yes you will output more insulin.. so if they have assumed its a fasting test it may look as though you are producing enough insulin

certainly the charts i looked at in the past when i was going through cpep tests indicated different criteria for fasting and non fasting