[homeschoolmom]

I'm confused about c peptide levels. When my dr. checked mine, it was low normal at .8. Does this mean it is impossible for me to have insulin resistance? Do any type 2s have a c-peptide this low (but still normal)? If I have some high blood sugar readings after eating, does it mean my body is not producing enough insulin? My dr. said that type 1's are either diabetic or not (in other words, there is no gradual road there like with type 2). Why do I have high blood sugar readings if my c- peptide is so low, and I'm not type 1?

[lilituc]

That sounds like your body is not producing enough insulin. It doesn't mean you can't have insulin resistance - just that high numbers wouldn't be caused by insulin resistance alone (i.e. Type 2), but that you're not producing enough insulin.

Did you get tested for antibodies? The doctor is right about regular Type 1, but it sounds like he doesn't know about LADA.

[Ronin]

Hi Homeschool Mom!

In my personal opinion, it is your MD who is confused. While all laboratories have slight variations in the reference levels, most of the labs I've looked at on the web show a "normal" C-Peptide as between 1 and 5. Yours is below "1" and, in my opinion, qualifies as below normal (the particular lab and the chemicals they use may be different.

Even if you are "Low-Normal" the stark reality is that it is highly unlikely that you are headed towards, let alone already a Type-2. However, there are MD's with the idea in their head that any and all adult onset cases of high BG levels must be Type-2's.

My advice is to find a credible endo and tell the MD you have to "take a hike."

As I've said many times on these forums, I know more than a few people treated as Type-2 who turned out to be Type-1.5 (adult onset Type-1) -- in short your pancreas is shutting down. There can be a number of reasons for the slowdown/shutdown but you don't need meds for Type-2 conditions because they won't work and will only give you the nasty side effects with no relief to the underlying condition.

Try swinging over to the Type-1.5 forum and talk to the folks there.

Yes, your body is producing some insulin but not nearly sufficient to what your diet requires.

The good news is that insulin, and usually in very small doses, works to correct the lack of insulin.

[Emm]

Totally agree - get thee to an endo! Ask the doctor to check things out properly and then he should want to send you to an Endo anyway. It's quite possible you're a slow onset type one (LADA, sometimes known as T1.5) which is much more common in adults than 'standard' type 1. Perhaps ask him to look it up and see what he thinks? (Doctors hate being told they're wrong or that you know what's up before they do... so you gotta ask, not tell!)

Keep your doctor in the loop - if they never experience a LADA they don't know what to look for and could make all the same mistakes again with the next patient. Better that he gets an education out of this I think.

[David_S]

My c-pep was under 3 when I was diagnosed with 1.5 at age 37. I am not type 2.. never was.. my pancreas shut down after an autoimmune attack on it. MY endo is the one who tested and diagnosed.. my family dr. .. well he was confused that my numbers were high.. over 600.. because I was tall and thin. He had no clue about 1.5 and put me on type 2 meds that did noting.. because I was not making insulin. So.. the endo is the one who got to the bottom of what I really had going on. Endo put me on insulin right in his office.. and my family dr. told me not to eat anything sweet.. ??

[homeschoolmom]

Thanks for the replies. My dr. did send me to an endo. who did an antibody test - result was negative. He wrote me a letter saying, "You don't have type 1 diabetes and it is unlikely that you will get it." My glucose tolerance test came back normal, with a 111 after 2 hours. BUT, if I eat a 6 inch subway sand, a handful of fries and some ice cream - 2 hours later I'm at 143!!! Why don't they just give you some fast food for a glucose tolerance test ????? It makes no sense to me. Is it possible that I truly am normal -just with some high readings after eating sometimes?

[BrianSCohen]

Homeschoolmom,

It can be hard to know whether a lower c-peptide test reflects lack of insulin production, or lack of insulin demand. Do you consistently eat low carb? If so, that can drastically reduce demand, reflecting in a low normal reading.

You eat a sub, fries and ice cream and are at 143 at two hours. That is likely > 100 g carbs in a meal (albeit with fat) and you are at 143 at 2 hours. You would likely pass a glucose tolerance test and would not be considered insulin resistant and certainly you produced enough insulin yourself to cover it.

You may very well have an emerging diabetic condition, but low normal c-peptide does not particularly indicate anything. I would suggest that you put more faith in you HbA1c which according to other posts is in the high normal range. You can safely follow a diet that is on the low side of the carb range and simply keep an eye on things (HbA1c). Don't worry yourself into a frenzy. Millions of americans have diabetes. Even if you do end up with diabetes, you can treat it with diet, exercise and medication and live a full and normal life.

[terryok123]

FROM Webmd:

C-Peptide
A C-peptide test measures the level of this peptide in the blood. It is generally found in amounts equal to insulin. Insulin helps the body use and control the amount of sugar (glucose) in the blood. Insulin allows glucose to enter body cells where it is used for energy. The level of C-peptide in the blood can show how much insulin is being made by the pancreas. C-peptide does not affect the blood sugar level in the body. See an illustration of the pancreas.

A C-peptide test can be done when diabetes has just been found and it is not clear whether type 1 diabetes or type 2 diabetes is present. A person whose pancreas does not make any insulin (type 1 diabetes) has a low level of insulin and C-peptide. A person with type 2 diabetes has a normal or high level of C-peptide.

A C-peptide test can also help find the cause of low blood sugar (hypoglycemia), such as excessive use of medicine to treat diabetes or a noncancerous growth (tumor) in the pancreas (insulinoma). Because man-made (synthetic) insulin does not have C-peptide, a person with a low blood sugar level from taking too much insulin will have a low C-peptide level. An insulinoma causes the pancreas to release too much insulin, which causes blood sugar levels to drop (hypoglycemia). A person with an insulinoma will have a high level of C-peptide in the blood.

Why It Is Done
A C-peptide test is done to:

Tell the difference between type 1 diabetes and type 2 diabetes.
Find the cause of low blood sugar (hypoglycemia).
Check to see whether a tumor of the pancreas (insulinoma) was completely removed.
How To Prepare
Do not eat or drink for 8 hours before your blood test.

Insulin and some oral medicines used to treat type 2 diabetes can change the test results. Your health professional may ask you to stop these medicines before your blood test.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How It Is Done
The health professional drawing your blood will:

Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
Clean the needle site with alcohol.
Put the needle into the vein. More than one needle stick may be needed.
Attach a tube to the needle to fill it with blood.
Remove the band from your arm when enough blood is collected.
Put a gauze pad or cotton ball over the needle site as the needle is removed.
Put pressure to the site and then a bandage.

How It Feels
The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Risks
There is very little chance of a problem from having blood sample taken from a vein.

You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.
Ongoing bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.
Results
A C-peptide test measures the level of this peptide in the body.

Normal
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.

C-peptide Fasting: 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.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:

Taking medicines, such as insulin, sulfonylurea medicines for type 2 diabetes, corticosteroids, diuretics, or birth control pills.
Using alcohol.
Having kidney failure. Both insulin and C-peptide are removed from the body by the kidneys. C-peptide levels may be high in a person with kidney failure.
Being obese. More insulin is made in obese people and can cause high levels of C-peptide.

What To Think About
A C-peptide test must be done at the same time as a blood glucose test. For more information, see the medical test Blood Glucose.
A person with new type 2 diabetes often has a normal or high level of C-peptide in the blood. Over time, a person with type 2 diabetes may develop a low level of C-peptide.
To help tell the difference between type 1 and type 2 diabetes and to help guide treatment, most health professionals look at a person's age, weight, and how long symptoms have been present. In rare cases, a C-peptide stimulation test may be done to help tell the difference between the two types of diabetes. During a C-peptide stimulation test, a blood sample is taken to measure C-peptide. Then a shot of a hormone to increase blood sugar (glucagon) is given into a vein in the arm. Another blood sample is taken. In people with type 1 diabetes, C-peptide levels will be low because the pancreas cannot make any insulin in response to the glucagon. In people with type 2 diabetes, C-peptide levels will be higher than the first blood test because the pancreas is making more insulin in response to the glucagon.
Other Works Consulted
Chernecky CC, Berger BJ, eds. (2004). Laboratory Tests and Diagnostic Procedures, 4th ed. Philadelphia: Saunders.

Fischbach FT, Dunning MB III, eds. (2004). Manual of Laboratory and Diagnostic Tests, 7th ed. Philadelphia: Lippincott Williams and Wilkins.

Pagana KD, Pagana TJ (2006). Mosby’s Manual of Diagnostic and Laboratory Tests, 3rd ed. St. Louis: Mosby.