​MDAE E​46: Why the C-Peptide Test is the Most Important Diabetes Blood Test

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Podcast Transcript

Cyrus Khambatta, PhD: Welcome to the Mastering Diabetes Audio Experience, where we teach you how to sit in the driver's seat of your diabetes health for the rest of your life. We'll teach you how to reverse insulin resistance, achieve your ideal body weight, gain energy and get your best A1c following more than 85 years of evidence-based research in the Mastering Diabetes Program.

Robby Barbaro: Our program teaches you how to reverse prediabetes and type 2 diabetes, and how to simplify your life with type 1 diabetes by maximizing your insulin sensitivity, using food as medicine.

Cyrus Khambatta, PhD: We're on a bold mission to reverse insulin resistance in 1 million people. We're glad to have you joining us.

Robby Barbaro: Welcome to the Mastering Diabetes Audio Experience. I am really excited about today's episode. We have incredibly important information we're going to be covering, and it's information that's not talked about enough in the world of diabetes health. So, we're glad to be covering it.

This is a very detailed episode, you're going to learn everything you need to know about the C-Peptide test. You're gonna learn exactly what is C-Peptide, why is your C-Peptide important, and how this impacts the type of diabetes you're living with.

So, we've had the opportunity to work with thousands of people living with diabetes. And I gotta say, one of the biggest surprises in doing so, has been seeing how many people are blatantly misdiagnosed. Just flat out the wrong diagnosis, because the doctor did not run sufficient number of tests, and just made some assumptions. So, you're going to learn all about how that happens, and how to prevent that in today's episode, by gaining this knowledge. You become the master of your own health when you have this type of knowledge.

So, you are also going to learn about how beta cells get damaged, and how you can assess that, and then see whether or not you can completely reverse type 2 diabetes or not. What is type 1.5 diabetes. What’s the criteria for type 1 diabetes. All those details are going to be covered in this episode. We address doctors not prescribing this test as often as necessary. We also talked about how to interpret your results. And we tell you how you can get your C-Peptide tested.

So, this is all information that's coming from an article that's on our website masteringdiabetes.org, we will hyperlink the article below this episode. So, we highly suggest reviewing that. You'll see the charts there, you'll see the links to using different services for actually getting your C-Peptide tested. All that's on the website. And all that information is on the website, and of course, a lot more as well. So, I hope you enjoy this episode. Let's get started.

Robby Barbaro: Have you ever heard of the C-Peptide test? It turns out that your C-Peptide is an important indicator of your diabetes health. And one of the most important of all diabetes biomarkers. We’ll cover the basics of C-Peptide biology. Explain what it tells you about your body's ability to secrete insulin, how it helps you understand what type of diabetes you're living with, as well as where and how to get your C-Peptide tested easily.

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Cyrus Khambatta, PhD: What exactly is C-Peptide? When the beta cells in your pancreas secrete insulin, they secrete it as a molecule known as proinsulin. Now, proinsulin is an immature version of insulin that's comprised of an alpha chain, a beta chain, and a C-Peptide connector. Now, when C-Peptide is removed from the proinsulin molecule, proinsulin turns into insulin. And insulin has very specific and powerful biological activities in your blood and tissues.

Now, insulin and C-Peptide are made in equal amounts, and C-Peptide remains in your blood for substantially longer periods of time, than does insulin. What this means is actually quite simple: C-Peptide and insulin are present in pancreatic beta cells, and in your blood in equal amounts, however, C-Peptide has a substantially longer half-life than insulin, which is about 20 to 30 minutes, versus three to five minutes for insulin.

So, this means that C-Peptide remains in your blood for approximately five times as long as insulin, and is therefore, present in your blood at approximately five times the concentration. And because insulin is degraded quickly, measuring your C-Peptide value is easier, because it sticks around for a longer period of time, and is used as a surrogate for the amount of insulin that your pancreas actually produce.

Robby Barbaro: Why is your C-Peptide important? Because C-Peptide is directly related to insulin production, understanding whether beta cells are capable of secreting sufficient amounts of insulin to meet your body's metabolic needs is an absolutely crucial piece of information.

In fact, understanding your C-Peptide value is so important, that researchers believe it to be the most suitable measurement for assessing endogenous insulin secretion. Therefore, knowing your C-Peptide level is crucial in understanding what type of diabetes you have.

Since the treatment of type 1, type 1.5, prediabetes, type 2, and gestational diabetes each require different treatment plans, being misdiagnosed with the incorrect type of diabetes can lead to an improper course of treatment, years of frustration, and rapidly declining. An accurate C-Peptide measurement will provide you, and your doctor, with a quantitative assessment of the ability of your pancreatic beta cells to secrete insulin.

Cyrus Khambatta, PhD: Question number one: What type of diabetes are you actually living with? Every year millions of people are misdiagnosed with type 2 diabetes, rather than type 1 diabetes, or type 1.5 diabetes, because they fail to measure their C-Peptide value at an early stage after diagnosis.

The C-Peptide test will tell you what type of diabetes you are actually living with, and will help you differentiate between an autoimmune version of diabetes with extremely low insulin production, or a lifestyle related diabetes with medium to high insulin production.

Now, recent guidelines dictate that a C-Peptide test should be used when there is doubt about what type of diabetes a patient is living with. In addition, a recent systematic review suggested that C-Peptide be used as the principal baseline measure of insulin deficiency. Knowing your C-Peptide value can determine your entire course of your diabetes treatment, and allow you to differentiate between an insulin sufficient state, and an insulin deficient state.

Although it is possible to make an educated guess about what type of diabetes you are living with, a C-Peptide test gives you, and your doctor, much more, and much more accurate information into your overall diabetes health.

Are you living with autoimmune diabetes? Now, if you are living with an autoimmune version of diabetes, either type 1, or type 1.5 diabetes, then your C-Peptide value will most likely be significantly lower, than if you are living with prediabetes, or type 2 diabetes. But what exactly is type 1.5 diabetes? So, type 1.5 diabetes is increasing in prevalence around the world, and is often referred to as Latent Autoimmune Diabetes in Adults or LADA.

Once considered a rare condition, type 1.5 diabetes has been on the rise since the 1950s. Now, living with type 1.5 diabetes, which is an adult onset, slow progressing version of type 1 diabetes, means that your pancreas is still capable of producing insulin, but the presence of one or more autoantibodies against beta cells, leads to a slow and progressive decline of beta cells over the course of time. Now, LADA has characteristics of both type 1 diabetes, and type 2 diabetes and is often misdiagnosed as other forms of diabetes, resulting in the wrong treatment protocol.

It is currently unknown how many people are living with type 1.5 diabetes around the world, and how many people have been misdiagnosed with other forms of diabetes. But some estimates could be as many as 1 out of every 10 patients living with diabetes, and some researchers believe that type 1.5 diabetes is the most prevalent form of all autoimmune type diabetes in general, therefore more prevalent than type one diabetes.

The Immunology of Diabetes Society has established 3 main criteria for establishing a diagnosis of LADA, including: Number one, being greater than 30 years old at the time of diagnosis. Number two, testing positive for at least one islet cell autoantibodies. And, number three, having no insulin requirement for at least six months after diagnosis.

In contrast, those living with type 1 diabetes experience a severe and rapid loss of insulin secretion, characterized by multiple autoantibodies, and a dangerously low C-Peptide value. An overwhelming majority of those living with type 1.5 diabetes, test positive for only one autoantibody, resulting in a slow progressing loss of insulin secretion over time. Those living with type 1 diabetes often require exogenous insulin, almost immediately after diagnosis, whereas those with type 1.5 diabetes may not require insulin therapy for six months to five years after diagnosis.

It turns out that people with LADA are often misdiagnosed with type 2 diabetes for three main reasons. Number one, diabetes onset occurs during adulthood. Number two, beta cell destruction and symptoms of the disease occur over the course of time. And number three, patients and doctors may have an incomplete understanding of their autoimmune status, and are lacking a diabetes autoantibodies panel to test for the auto antibodies known as: GADA, IAA, IA-2A, ICA, and/or ZnT8. Now, these are all just acronyms for specific autoantibodies that are present in autoimmune diabetes.

Type 1.5 diabetes is also likely in patients diagnosed with type 2 diabetes as an adult, who are lean and do not have any symptoms of the metabolic syndrome, especially if that patient follows a low-fat, plant-based, whole-food diet, and is physically active. Because a low-fat, plant-based, whole-food diet is so effective at preventing and reversing type 2 diabetes. If you are unable to control your blood glucose after approximately three months, then we recommend testing your C-Peptide and getting a diabetes antibody panel immediately. We recommend getting your C-Peptide tested first, once you have that information, you can then decide if it's worth the time and effort to test for diabetes antibodies.

Robby Barbaro: Question number three: How much damage have your beta cells accumulated over time? Knowing how much damage has been done to your beta cells over time is an important determinant of whether your body requires exogenous insulin, or not. If your beta cells are still functioning properly, a low-fat, plant-based, whole-food diet combined with frequent exercise, and adequate sleep, can help you achieve non-diabetic blood glucose, without the need for medications or insulin injections.

If your C-Peptide test reveals significant destruction of your pancreatic beta cells, it is unlikely that you will be able to achieve non-diabetic blood glucose values without the use of exogenous insulin, regardless of how strict you are with your diet and exercise regimen.

If you have been diagnosed with type 2 Diabetes on the assumption that you are insulin resistant, even though your C-Peptide value was never tested, then taking a C-Peptide tests can help you avoid unnecessary oral diabetes medications and years of unnecessary side effects.

Question number four: What are your chances of reversing prediabetes, or type 2 diabetes, without the need for diabetes medications? Using conventional treatment, type 2 diabetes is a progressive disease in which approximately 50% of individuals require insulin therapy within 10 years of diagnosis. This results from insulin resistance, the deterioration of beta cell function, and reduced insulin secretion over time. Using a low-fat, plant-based, whole-food diet, combined with adequate physical exercise, you can reverse prediabetes and type 2 diabetes in 99% of cases, when there is still sufficient insulin production.

In this case, your body is producing plenty of insulin, but your lifestyle has created a state of insulin resistance. By optimizing your diet, and movement patterns, you can reverse insulin resistance and control your blood glucose without diabetes medications.

A high C-Peptide value indicates that your beta cells are capable of manufacturing sufficient insulin, and by switching to a low-fat, plant-based, whole-food diet. It's possible to completely reverse insulin resistance, and eliminate your need for diabetes medications, using your food as medicine.

A medium C-Peptide value indicates that you have adequate insulin production to fully reverse prediabetes or type 2 diabetes, but that it's imperative to maximize your insulin sensitivity in order to prevent your beta cells from becoming exhausted over time.

A low C-Peptide test means that your beta cells have been permanently impaired. In this situation, you will likely require exogenous insulin to control your blood glucose.

If you are living with type 2 diabetes, and have been told to inject insulin unaware of your C-Peptide value, then you are in the same situation as millions of people around the world. The vast majority of these patients have a medium or high C-Peptide value, and can fully reverse insulin resistance using lifestyle medicine.

However, while it's true that type 2 diabetes can often be fully reversed, this is not always the case. In the progression towards type 2 diabetes, beta cells in your pancreas can begin hyper secreting insulin, as early as 20 years before diabetes is even detected. This is done in an effort to prevent your blood glucose from elevating as a result of increasing insulin resistance. Insulin is not the limiting factor in early stages of the disease process. As insulin resistance progresses, beta cells increase insulin production, sometimes by as much as 500% of normal, in order to protect against elevated blood glucose.

Over time, if insulin resistance continues to develop, due to high fat feeding the beta cells in your pancreas become overworked, resulting in beta cell death. When this happens, you develop a state of impaired insulin production, resulting in high blood glucose in the fasting and post meal states.

Your C-Peptide values follow the same progression as insulin. When you're producing excess insulin, your C-Peptide value increases accordingly. And when beta cells permanently lose their ability to produce sufficient insulin, your C-Peptide value falls significantly. As long as you are not living with an autoimmune form of diabetes, there is strong scientific evidence showing that lifestyle change can help restore beta cell function. However, optimal function may never be completely restored. By testing your C-Peptide level, you and your doctor, can find out how much your beta cells are capable of secreting insulin, or if they have been permanently impaired.

Cyrus Khambatta, PhD: Question number five: What is the difference between a fasting and stimulated C-Peptide test? There are two types of C-Peptide tests. The first is a fasting C-Peptide test, which is performed after an overnight fast of at least eight hours. The second is a stimulated C-Peptide test, which is used to measure the amount of insulin that your pancreas is capable of manufacturing, in response to a high carbohydrate meal.

Now, the purpose of the stimulated C-Peptide test is to measure how much insulin your pancreas produced in the few hours after a carbohydrate challenge. The amount of C-Peptide in your blood reveals how effective your pancreas is at creating insulin, and C-Peptide, in response to a rising blood glucose.

Reference ranges for the stimulated C-Peptide tests are very simple. Less than two nanograms per milliliter means that a severe damage to the pancreas has occurred, with about a 5% chance of controlling blood glucose through lifestyle measures alone. Insulin injections in this situation are likely required.

If your stimulated C-Peptide test is between two and four nanograms per milliliter, then that indicates that some damage to your pancreas has occurred, with about a 50% chance of controlling blood glucose without the use of insulin.

If your stimulated C-Peptide value is greater than four nanograms per milliliter, this indicates that the pancreas is still functioning well, with about a 95% chance of controlling your blood glucose through lifestyle measures alone.

Here at Mastering Diabetes, we believe that your doctor can be your greatest ally in restoring your health. For this reason, we educate our clients on how they can partner with their doctor to maximize their metabolic health. Despite the advancements that have been made in understanding, and treating diabetes over the past century, lifestyle change education for physicians is often lacking in medical school. Because of this, physicians are unaware of the power of lifestyle change, and are rarely educated about the importance of a C-Peptide test for their patients.

In addition, much of the medical school education, as well as postgraduate continuing education, is funded by pharmaceutical companies. Now, these companies have a vested interest in ensuring that type 2 diabetes patients remain unaware that their condition is preventable and reversible with a low-fat, plant-based, whole-food diet. Always remember one thing, physicians are not to blame for a lack of education about lifestyle change. Until the medical system begins to place a larger emphasis on evidence-based approaches to reversing diabetes, physicians will continue to remain in the dark.

Robby Barbaro: It's very easy to get your C-Peptide level tested. It's an inexpensive blood tests that you can request from your doctor, or you can order the test for yourself, online, and scheduled to have your blood drawn at a local Labcorp or Quest Diagnostics walk-in facility.

You can usually schedule your blood draw for the same day you place your order, and there is little, to no way time. Most facilities are open on weekends, so paying out of pocket is often more convenient than waiting to see your primary care physician or endocrinologist.

If you're going to use the latter method, we suggest ordering from one of the following online laboratories: Option number one, Request a Test. Option number two, Direct Labs. Option number three, Personal Labs. Simply select where you would like to get your blood drawn, enter your credit card information, and then take the order form to your local facility. The results are quick and often ready in 1 to 3 days.

Cyrus Khambatta, PhD: Now, we recommend using the following guidelines to interpret your C-Peptide test results. As you can see, your C-Peptide results are best interpreted in conjunction with an islet antibody test. Interpreting the results of both tests together, provides you and your doctor, with the most accurate information.

If your fasting C-Peptide is less than one nanograms per milliliter, that means that your endogenous insulin production is very low, which means that you fall into one of the following three categories. Number one, if you test negative for islet antibodies, then you are likely living with insulin dependent type 2 diabetes with a low insulin production. You're likely to require both basal and bolus insulin in order to control your blood glucose. If you test positive for one islet antibody, and are over the age of 30, then you're likely living with type 1.5 diabetes and may require both basal and bolus insulin to control your blood glucose. If you test positive for multiple islet antibodies, irrespective of how old you are, then you're likely living with type 1 diabetes and may require both basal and bolus insulin to control your blood glucose.

If your fasting C-Peptide is between one and two nanograms per milliliter, then that means that your endogenous insulin production is medium, which means that you fall into one of the following three categories. Number one, if you test negative for islet antibodies, then you are likely living with type 2 diabetes, with an impaired insulin production. Adopting a low-fat, plant-based, whole-food diet to maximize your insulin sensitivity, is your best chance at remaining free of exogenous insulin, over the course of time. If you test positive for one island antibody, and are over the age of 30, then you're likely living with type 1.5 diabetes and may experience a decline in your insulin production, with an increased need for exogenous basal and bolus insulin over time. If you test positive for multiple islet antibodies, irrespective of how old you are, then you're likely living with type 1 diabetes and are currently in the “honeymoon phase”, in which your endogenous insulin production is on the decline. You will likely experienced an increased need for exogenous basal and bolus insulin over time.

If your fasting C-Peptide is two nanograms per milliliter or above, then your endogenous insulin production is medium to high, which means that you fall into one of the following three categories. Number one, if you test negative for islet antibodies, then you're likely living with type 2 diabetes, with a high insulin production. You're likely to remain free of exogenous insulin, as long as you continually improve your insulin sensitivity. If you test positive for one islet antibody, and are over the age of 30, then you're likely living with type 1.5 diabetes and may experience a decline in your insulin production, with an increased need for exogenous basal and bolus insulin over time, even though your endogenous insulin production is sufficient at this point in time. And if you test positive for multiple antibodies, irrespective of how old you are, then you are likely living with type 1 diabetes, and are currently in the “honeymoon phase” in which your endogenous insulin production is declining quickly, even though your endogenous insulin production is sufficient at this point in time. You're likely going to experience an increased need for exogenous basal and bolus insulin over the course of time.

So there you have it, everything you ever wanted to know about your C-Peptide value. If you enjoyed this video, click on the thumbs-up button, subscribe to the channel, and leave a comment below and tell us if you've ever been confused about your C-Peptide value. We'll do our best to help in any way that we can.

Cyrus Khambatta, PhD: We hope you enjoyed this episode, and can apply some of these principles to your personal life. Now, we have an Online Group Coaching Program that has helped thousands of people living with all forms of diabetes, reverse insulin resistance, drop their A1c, lose weight, and gain tons of energy. And also reduce their need for oral medication and insulin using, their food as medicine.

We like to call ourselves the world's most robust, and ridiculously affordable, Online Coaching Program for people with diabetes. And we've helped people living with type 1 diabetes, type 1.5 diabetes, prediabetes, type 2 diabetes, and gestational diabetes living all around the world.

Now we provide you with three tools that are specifically designed to put you in the driver's seat of your diabetes health. The first is an Online Course that gives you step by step instructions on how to change your diet. Starting with breakfast, then lunch, then dinner.

We teach you exactly which foods to increase, which foods to limit, and which foods to avoid entirely. The course is designed with you in mind. We provide you with relevant information, and we do our best to reduce overwhelm, because we know just how confusing the internet can be these days, when searching for simple ways to improve your blood glucose control.

The second tool is even better than the first. We provide you with access to our online community, with thousands of people that are going through this process with you. You'll be able to interact with our team of coaches, including Kylie Buckner, a Registered Nurse who is brilliant. She also happens to be my wife, and is one of the most kind and compassionate human beings that I've ever met. Adam Sud. He reversed type 2 diabetes. He lost more than 160 pounds and he de-addicted himself from both food and prescription medication at the same time.

You'll also get to interact with Mark Ramirez, who lost more than 50 pounds, reversed type 2 diabetes, and is a certified Food For Life Instructor, through the Physicians Committee for Responsible Medicine. You'll also get the ability to interact with both Robby and myself in the online community. And we guarantee that we’ll answer your question within 24 hours to help you solve problems in real time.

The third tool is a twice monthly Q&A video conference, where you can ask our team of coaches any question that you have about your personal program, and meet others that are going through this process with you. Now, we're proud to say that our coaching program is very popular, and because of that, we've instituted a waiting list to join. The reason we created the waiting list in the first place is because we have more than 2000 active members in our program and want to provide excellent service to our existing members. You can still join the program, but in order to do so you have to put yourself on the waiting list and you'll be notified of when we open next. When we do, we'll send you a personal invitation to join.

To join the waiting list simply go to masteringdiabetes.org and click on Coaching in the navigation bar at the top of the screen, or click the link below in the show notes. We can't wait to help you transform your diabetes health from the inside out. We hope to see you on the inside.

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About the Author

Cyrus Khambatta, PhD, and Robby Barbaro are the co-founders of Mastering Diabetes, a coaching program that reverses insulin resistance via low-fat, plant-based, whole-food nutrition. Cyrus has been living with type 1 diabetes since 2002 and has an undergraduate degree from Stanford University and a PhD in Nutritional Biochemistry from UC Berkeley. Robby was diagnosed with type 1 diabetes in 2000 and has been living a plant-based lifestyle since 2006. He worked at Forks Over Knives for six years, is studying towards a master’s degree in public health, and enjoys sharing his lifestyle on Instagram, YouTube, and Facebook.