AskNadia: Should I Be Concerned About My Son’s Elevated C-peptide Test?

 Dear Nadia,

I’m extremely frustrated. My 15 year old son has acanthosis nigricans, which he has had for a couple of years, along with skin tags. My doctor has tested him for diabetes twice and the tests have come back normal. This week I insisted that we run more tests because he had been sick more often than normal this year. She tested for tons of stuff but everything came back normal except that his C-peptides were elevated. His hemoglobin was normal, too. 

 He had always been big. During pregnancy they cut me off sugars at 23 weeks because of his size and took him out two weeks early. He was still big: 9 lbs, 3 oz. He is now 6’3,″ weighs 315 lbs and has a size 17 shoe. And those measurements are with him having dieted for the past three weeks and losing 20 lbs. (Testing was done during this time too, while he has been eating clean). My doctor doesn’t want to send him to an endocrinologist. Should I be concerned with his elevated C-peptide results? Normal range is 2.0 to 4.4; his was a 5.9.

 Thank you for any advice.



Dear April:

C-peptide is a 31-amino peptide secreted by pancreatic beta cells alongside the production of insulin. The body needs amnio acids to function and repair body tissue. The pancreas manufactures two types of peptide chains: chain A and chain B. By itself, each form of insulin cannot aid digestion. C-peptide binds the two to produce insulin the body can metabolize.

High levels of C-peptide indicate high levels of insulin production. However, high insulin levels do not always indicate the absence of type 2 since the body may have become insulin resistant.

A Normal C- peptide range is 0.5 to 2.0 nanograms per milliliter. A low-test result may signal Type 1 diabetes. Conversely, a high C-peptide result may be an indicator of type 2 diabetes. 

The acanthosis nigricans you mentioned is a skin disease caused by the presence of too much insulin. Since insulin levels almost always correspond to the levels of C-peptide, your son’s skin condition would seem to indicate that his pancreas is producing large amounts of insulin. 

A 20-lb. weight loss in three weeks puts a huge demand on your son’s body, no matter how physically strong he is. Insulin is a growth hormone. Sustaining optimal help will require a team approach. Working with a healthcare professional that has experience in this particular field will offer you both ease of mind.

Elevated C-peptide levels can also indicate a kidney problem or a pancreatic tumor. (Most such tumors are non-cancerous.)

I’m assuming that your son’s doctor is a general practitioner who has broad experience dealing with various common medical problems. She may not be aware that she is not as well versed as a diabetes specialist. Tell your current physician that you would like a second medical opinion from an endocrinologist. 

It’s possible that you are in an HMO where doctors try to avoid sending patients to specialists as much as possible. If that’s the case, you may have to take matters into your own hands by calling your health plan administrator. Explain your situation to them and request a referral to an endocrinologist. When you get in to see the specialist,  make sure you have a complete medical history record  of your son’s lab test.   

I hope this helps you with your next exploration step.


Nadia’s feedback on your question is in no way intended to initiate or replace your healthcare professional’s therapy or advice. Please check in with your medical team to discuss your diabetes management concerns.
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About Nadia:
Nadia was not only born into a family with diabetes but also married into one. She was propelled at a young age into “caretaker mode,” and with her knowledge of the scarcity of resources, support, and understanding for people with diabetes, co-founded Diabetes Interview, now Diabetes Health magazine.
Nadia has received 19 nominations for her work as a diabetes advocate. She has been featured on ABC, NBC, CBS, and other major cable networks. Her publications, medical supply business, and website have been cited, recognized and published in the San Francisco Chronicle, The Wall Street Journal, Ann Landers advice column, former Chrysler chairman Lee Iacocca, Entrepreneur magazine, Houston NewsPhili.comBrand WeekDrug Topics, and many other media outlets.

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