C-Peptide results ?

[gogobroom]

Having been diagnosed Type 2 last Oct the NHS GP has been fantastic with lots of different tests and assistance, however the diagnosis has now sort of slowed due to not enough red flags for further investigations - so I decided to pay to get a C-Peptide test done privately, just received the results it was a fasted 10 hour test:

Normal range 0.73 - 4.37 ng/ml my result 0.62 ng/ml


Reading between the lines could this mean I am more likely heading down the route of Type 1.5 than Type 2 ? My understanding is that low C-peptide levels indicate decreased insulin production.

I'm athletic, normal body weight, extremely fit and do endurance sport - since diagnosis reduced my carbs to around 50gsm a day HBA1c is only just diabetic range.

Any thoughts on this ? I know you cant diagnose but based on your personal experience / knowledge

 

[Antje77]

C-peptide measures the amount of insulin produced.
In non diabetics, it produces the exact amount needed to keep normal BG levels.

This is why a C-peptide test is usually taken in tandem with a BG test:
High BG + normal or low C-peptide = not producing enough insulin.
Normal or high BG + high C-peptide = overproducing insulin.
Normal BG + normal C-peptide = not enough information if diabetic.

Now normal BG + lowish C-peptide shows the amount of insulin produced was exactly the amount needed at the time. You didn't need more insulin because of low carbing.
It shows you're not overproducing insulin, at least not on a low carb diet.
But it doesn't show if you cannot produce more insulin if needed.

Low C-peptide does usually indicate decreased insulin production, yes. But if the low amount of insulin you produced was enough, I'm not sure how significant this is.
I've read somewhere that C-peptide is best tested with BG over 8 mmol/l (no idea where), but I only read it after I had my C-peptide test.

Early on in T1, it can be very hard to differentiate between T1 and T2 because early T1's often keep producing insulin for quite some time.

 

[Bcgirl]

With that result I would go for a fasting insulin test also. If that number is below range then a 1.5 (LADA) might be something for your health providers to look at. Good luck

 

[Antje77]

With that result I would go for a fasting insulin test also. If that number is below range then a 1.5 (LADA) might be something for your health providers to look at. Good luck

What information does a fasted insulin test give you that a fasted C-peptide doesn't give you?
Not being critical, I just haven't looked into insulin tests because I thought C-peptide was more useful from what I read but don't remember exactly some years ago.

 

[Bcgirl]

They are similar but I would absolutely have the test for fasting insulin if my c peptide numbers were being questioned.
this test can indicate if you are insulin resistant (HOMA IR calculation) and a very low number would indicate type one.

 

[searley]

My ex recently had discussions about this.. the diabetes team at the hospital would only accept results from an non fasting test, and took a bg at the time which had to be in excess of 6 or they would reject the c peptide test

 

[oldgreymare]

My ex recently had discussions about this.. the diabetes team at the hospital would only accept results from an non fasting test, and took a bg at the time which had to be in excess of 6 or they would reject the c peptide test

Similar to @searley's comment, I've been told that c-peptide and BG levels should be tested at the same time and should be non fasting and from a diet of at least moderate carbs for several days before testing. Fasted or low carb/keto eating before the test may not provide enough information to assess your 'native' insulin response.

 

[searley]

Similar to @searley's comment, I've been told that c-peptide and BG levels should be tested at the same time and should be non fasting and from a diet of at least moderate carbs for several days before testing. Fasted or low carb/keto eating before the test may not provide enough information to assess your 'native' insulin response.

Or another way to put it…. You body only produces the insulin needed, so if you starve yourself before going the body may not produce insulin and will give an artificially low result

Having food within a couple of hours before will give an accurate count as the bad had had to produce insulin

 

[gogobroom]

Thanks - I will speak to my doc at next appointment - just tyring to research prior to that. The general test for C-Peptide is fasted so there must be a specific reason for this, will find out from Doc.

 

[jonathan183]

There are different ways of doing a C-peptide test see here.
The combination of C-peptide and blood glucose concentration are required, not just the C-peptide concentration.
I suggest you get back in touch with the organisation who performed the test for you for the full information and also to provide guidance on what the results mean.
Normal/low blood glucose and high C-peptide could indicate insulin resistance - but may not be the only cause.
High blood glucose and low C-peptide would suggest low insulin production - would indicate type 2 is unlikely.

The purpose of the testing is to establish the most appropriate treatment - if the test results don't impact the treatment they are of limited use.

 

[Breadvan]

They are similar but I would absolutely have the test for fasting insulin if my c peptide numbers were being questioned.
this test can indicate if you are insulin resistant (HOMA IR calculation) and a very low number would indicate type one.

Where can you get a homa-IR test done?