Does anyone here know how to read the results of a cpeptide test.

Thanks Shannon for responding.Here’s the story:- After fasting for 12 hours I had the lab take my blood for a cpeptide test. Then I went to Dennys and downed a Large breakfast of the most awful stuff, sugar flour, potatoes, eggs, sausages etc. Two hours later I went back to the lab and had my blood drawn again.

Fasting result was 0.6
Post prandial was 1.3

Could this be interperated as normal ? or for the post prandial what would be a non diabetics result.

A C-peptide test measures the level of this peptide in the body.

Normal values vary from lab to lab. The level of C-peptide in the blood must be read with the results of a blood glucose test. Both these tests will be done at the same time.

0.78–1.89 nanograms per milliliter (ng/mL) or 0.26–0.62 nanomoles per liter (nmol/L)

High values
High levels of both C-peptide and blood glucose are found in people with type 2 diabetes or insulin resistance (such as from Cushing’s syndrome).
A high level of C-peptide with a low blood glucose level may mean an insulin-producing tumor of the pancreas (insulinoma) is present or that the use of certain medicines such as sulfonylureas or meglitinides is causing the high level.
If C-peptide levels are high after an insulinoma is taken out, it may mean that the tumor has returned or that the tumor has spread to other parts of the body (metastasized).
Low values
Low levels of both C-peptide and blood glucose are found in liver disease, a severe infection, Addison’s disease, or insulin therapy.
A low level of C-peptide with a high blood glucose level is found in people with type 1 diabetes.
Removal of the pancreas (pancreatectomy) causes a C-peptide level so low it cannot be measured. The blood glucose level will be high.


If that normal range which Shannon provided is for fasting–which I believe it is, your C-peptide looks like you might be low on insulin. Your post-meal value would be normal for fasting, but not for post-meal.

My doctor told me that the C-peptide was not a reliable guage to how much insulin we are making, though, and that its primary use is to see IF we are making insulin.

Does anyone know if taking Lantus or a long lasting insulin before a c-peptide test would affect the results?

I think the idea here is that if you are injecting insulin you might shut down your natural insulin production.

But whether that natural production would bounce back just because you missed a shot is a huge question. It might well take a while for it to upregulate if it had been suppressed. That’s how most other hormones work. If you supplement them, your natural production decreases and you have to be weaned off the supplemental hormone (cortisone, for example) very slowly and very carefully because the natural production does NOT come back on right away and in the case of cortisone, you can end up seriously ill as a result.

hmmm… well, I am honestly trying to learn all I can about how things work. I am not Type 1, I have Type “other” and the major causes (there are many), on a cellular level of why I have diabetes is unknown. Eventually when my pancreas has self-destructed enough, I will have a reduced c-peptide. But right now it is in the normal range (causing an insurance denial for an insulin pump). I had my Lantus that day, but was not sure if I should have taken it or not.

As a side note, my doc says it takes at least three days for Lantus to start working like usual (lack of better word) in the body after skipping just one dose. I have accidentally had the chance to test it out recently and it took me about 4 days. But that’s just me! :slight_smile:

This is rather curios…when your cpeptides were in the normal range (and what were they, by-the-way) what was your blood sugar reading. “Unknown” !!! I am over 60yrs old and “They” have been working on this before I was born. Not too much is new. smaller needles, synthesised insulin and some fancy momentary blood sugar meters. Have you read about the doctor doing duodenum by-passes for people to loose weight who discovered that this proceedure cured their diabetes.
About ten years ago when I was 250+mg/dL every day, one good enema would straighten out my BS for at least 8 to 12 hours. A lot of this is all about money,

Nope…no effect according to info from the internet, only when your pancreas produces insulin cpeptides are generated and used as markers.

I had some saliva and blood hormone tests done before I started taking insulin last september.
All four cortisol readings were high.
Morning 12.9 3.7 -9.5
noon 3.6 1.2 - 3.0
evening 6.2 0.6 - 1.9
night 2.4 0.4 - 1.0

I am thinking that to dig into the hormone problem is a step in the right direction…I just don’t have the money it takes to keep having all those tests done.

You can goodle this one. It’s not supposed to affect the result altho you will find one explanation trying to reason out a way that it might.

Sorry for hijacking your thread Carl. :slight_smile:

I have cystic fibrosis related diabetes (CFRD). Cystic Fibrosis causes super thick and sticky mucus all over the body mainly affecting the lungs and pancreas. As better treatments have come out we cystics are living much much longer and are having other complications, such as CF related diabetes. There aren’t any cases of CFRD published before 1993 I believe, so it is relatively new compared to Type 1 and Type 2.

Researchers do know that this is caused partially from some insulin resistance (due to stress from very frequent infections) and also since the pancreas becomes further and further damaged due to thick secretions (auto-digesting) there may be a lack of islet cells. I also found a study that claims the the islet cells in a cystic may function differently than normal (I had a hard time understanding the paper).

It is quite complicated and quite fascinating. It’s a new complication. There are relatively few of us (about 4,000 in the US) who has CFRD, so studies are hard to come by. Plus, lack of funding… I could go on and on.

Thanks for asking.

BTW, I do not know my c-peptide test result. I didn’t ask my nurse because I have been so focused on fighting my insurance. I do know my blood glucose was 117 at the time, but the lab didn’t test it.

Yummy and I used the excuse to the fullest.I have been three times to perhaps the most prestigeous diabetic clinic in Mass. and they have not once even suggested that they should do a test to see if I make any insulin at all. To my way of thinking, they are not very interested in the mechanics or the medicin except to get you on as much stuff as they can.


Funny…different docs different ideas. Wish I could finf one who really thought outside the box.

Last year I gave in and quit on 12 years of going it alone with blood sugars so high I wont even mention them on here/

Salty…Thanks for your response. You said:-

“I also found a study that claims the the islet cells in a cystic may
function differently than normal (I had a hard time understanding the

could you point to or send me a copy of this study…
You also said:- “Cystic Fibrosis causes super thick and sticky mucus all over the body
mainly affecting the lungs and pancreas.”

I also have this thick
mucus problem amongst other strange body pains. itchyness and skin erruptions on top of my head that come and go.

What do you know about this thick mucus…it sort of started with stringy spit.

carl Lyon