C-Peptide results ?

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.

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

Bcgirl said:

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

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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.

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.

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

searley said:

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

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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.

oldgreymare said:

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.

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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

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.

Bcgirl said:

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.

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Where can you get a homa-IR test done?