C-peptide: Reference Range, Interpretation, Collection And Panels
C-peptide is a peptide composed of 31 amino acids. It is released from the pancreatic beta-cells during cleavage of insulin from proinsulin. It is mainly excreted by the kidney, and its half-life is 3-4 times longer than that of insulin. The reference range of C-peptide is 0.8-3.1 ng/mL (conventional units), or 0.26-1.03 nmol/L (SI). [ 1 ] Hypoglycemia due to insulin-like growth factor secreting tumor Patient instructions: Overnight fasting is indicated Collection tube: Red-top tube or gel-barrier tube Unacceptable conditions: Grossly hemolyzed specimens Specimen preparation: Separate serum from cells and transfer to transport tube Storage/transport temperature: Refrigerated Stability: Refrigerated, 2 weeks; Frozen, 2 weeks C-peptide is a peptide composed of 31 amino acids. It is released from the pancreatic beta-cells during cleavage of insulin from proinsulin. It is mainly excreted by the kidney, and its half-life is 3-4 times longer than that of insulin. The insulin precursor, preproinsulin, is produced in the rough endoplasmic reticulum of pancreatic beta-cells and is later cleaved to proinsulin and transported to the Golgi apparatus, where is packed into secretory granules. During maturation of this granules, proinsulin is cleaved into 3 peptide chainsinsulin (2 chains, A and B) and C-peptide. Although, historically, C-peptide was considered to have no biologic activity; recent studies suggest that C-peptide may improve capillary blood flow in the feet, decrease urinary albumin excretion, and improve nerve function in individuals with type 1 diabetes. [ 2 , 3 ] } [ 4 , 5 ] C-peptide should be measured in the combination of insulin and proinsulin as part of the workup for nondiabetic hypoglycemia to differentiate between insulin-dependent hypoglycemia (high C-pepti Continue reading >>
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Why Does A C-peptide Test Matter?
I've used an insulin pump for 4 1/2 years (and been insulin dependent for 24 years). After I turned 65, Medicare was paying for my insulin and pump supplies. Recently, though, Medicare denied payment, saying my C-peptide level doesn't meet its criteria. Why does Medicare use a C-peptide test to make this decision? Russell Young, Morton, Illinois Jill Weisenberger, MS, RD, CDE, responds: The goal of an insulin pump is to mimic the insulin secretion patterns of a person without diabetes. Insulin pumps help people with diabetes achieve tight blood glucose control, which helps prevent some of the complications of diabetes. What to Know: Medicare covers the cost of using a pump only for people with proven type 1 diabetes or those whose insulin production is extremely low. Measuring C-peptide helps doctors determine how much insulin your pancreas produces. The insulin that comes from your pancreas starts off as a larger molecule called proinsulin. Proinsulin then splits into two pieces: insulin and C-peptide. Low C-peptide suggests there is little insulin production. Having no C-peptide indicates that you produce no insulin. (The insulin you inject or get with your pump is not associated with C-peptide.) It appears that Medicare denied coverage of the cost of your pump supplies because you produce more insulin than meets the criteria for use of a pump. Possible Solutions: As you know from the time before you had a pump, multiple daily injections (MDI) of insulin can also mimic a healthy pancreas. MDI requires that you take a long-acting insulin to provide some insulin 24 hours per day. Additionally, you will take rapid-acting insulin with meals and perhaps with snacks. Just as you adjust the amount of insulin your pump delivers, you can adjust the amount of rapid-acting insu Continue reading >>
What Is C-peptide And Why Does It Matter For People With Type 1 Diabetes?
Its a fantastic question and was a test that was run on me to confirm my type 1 diagnosis. A c-peptide! What is it? What is the purpose and why do they use this particular test in order to confirm a type 1 diabetes diagnosis? Lets take a closer look! What Is C-Peptide? C-peptide, similar to the hormone insulin is produced in the pancreas. Both are released simultaneously from the pancreas where a compound called pro-insulin is split into two pieces. As we are aware by now, Insulin is responsible for regulating the body’s glucose levels. Glucose, the body’s main source of energy, is a sugar that comes from foods. After a meal, our bodies break down the foods we eat into glucose and other nutrients, which are then absorbed into the bloodstream to give us the energy we need in order to fuel our bodies. Glucose levels in the blood rise after a meal and trigger the pancreas to make insulin and release it into the blood, and when insulin is released, so is C-peptide. Although both are released into the blood stream simultaneous, C-peptide has zero effect on our blood sugar levels. That being said, it is extremely useful as its used as a marker of insulin production, since the pancreas typically releases C-peptide and insulin in about equal amounts. In a nut shell, high C-peptide levels are associated with increased insulin production, while low C-peptide levels indicate decreased insulin production. How Is A C-Peptide Test Performed? Its really a simple test that needs to be performed and can get done right at your endocrinologist office. To measure level of c-peptide a fasting blood test is taken. You will be asked not to eat or drink (certain fluids) for 8 to 12 hours before the test. Also, if you take blood glucose lowering medication you will likely be asked to stop t Continue reading >>
C-peptide Test: Levels, Purpose, Procedure, And Results
The C-peptide test is a tool your doctor uses to monitor and treat diabetes . It shows how well your body makes insulin , which moves sugar (or glucose) from your blood into your cells. The test can help your doctor decide whether you need to take insulin to control your condition or to check your dosage if you already take it. Doctors can use the test whether you have type 1 diabetes , when the immune system attacks and destroys cells in the pancreas , or type 2, when your body doesn't use insulin as well it should. Beta cells in your pancreas make insulin. During that process, these cells also release C-peptide. This substance doesn't actually affect your blood sugar . But your doctor can measure the level of it to help her figure out how much insulin youre making. Doctors don't use it to actually diagnose diabetes , but it can give them a reading to help treat it. It can tell the difference between insulin your body has made and insulin that you took. To find out whether you have type 1 or type 2 diabetes When you have type 1 and your doctor needs to know how much insulin your pancreas still makes When you have type 2 diabetes and she needs to measure how much insulin you make on you own -- or whether you need to begin taking it yet To find out why you have low blood sugar (hypoglycemia) To diagnose a tumor of the pancreas that releases insulin, called an insulinoma You might need to stop eating 8 to 10 hours before the test. Sometimes, its done after you eat. Let your doctor know about any medicines you are on. Include medicine you take by prescription and those you buy over the counter, such as herbal supplements or vitamins. The C-peptide test uses a sample of your blood or urine . To take a blood test, someone in your doctors office or a lab places a needle into Continue reading >>
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C-peptide | Michigan Medicine
A C-peptide test measures the level of this peptide in the blood. It is generally found in amounts equal to insulin because insulin and C-peptide are linked when first made by the pancreas. 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. A C-peptide test can be done when 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 can have 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 but a high level of insulin. 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 when they have a high level of insulin. Help 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. Your doctor will give you instructions about eating and drinking before this test. Insulin and some oral medicines used to treat type 2 diabetes can change the test results. Your doc Continue reading >>
C-peptide Levels In Diabetes Management
Can C-peptide help attain adequate glycemic control in diabetes patients? C-peptide has served as a biomarker for understanding glycemic control in diabetes patients. Its role in normal physiology and diabetes serves mainly as an endogenous antioxidant that responds to rise in blood glucose despite normal uptake of glucose by peripheral tissues. Under normal physiologic conditions, C-peptide is synthesized from the cleavage of proinsulin, which yields insulin and C-peptide. Once stored in pancreatic beta cells, both of these byproducts are released in equimolar amounts in response to rises in glucose. However, this effect is not seen in type 1 diabetes patients due to lack of insulin, which can be a predisposition for patients to develop microvascular and macrovascular complications. The postulated mechanism by which this vascular injury occurs is thought to be attributed to the toxic effects of hyperglycemia, which can precipitate the formation of reactive oxygen species, leading to oxidative stress and apoptosis. Thus, C-peptide can counteract these oxidative effects and reduce inflammation in the vascular endothelium, hence improving blood flow in certain tissues and organs. Based on the hypothesized mechanism by which C-peptide works, researchers have focused on expanding the role of C-peptide in diabetes patients. In a double-blind randomized control trial, patients with type 1 diabetes and incipient nephropathy received C-peptide for 4 weeks. At the 2-week and 4-week mark, glomerular filtration and kidney blood flow were improved. Similar effects have been found after administering C-peptide for 3 months and improvement in albuminuria were noted. The role of C-peptide in retinopathy has shown promising results through VGEF regulation; however, clinical studies inv Continue reading >>
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A Practical Review Of C-peptide Testing In Diabetes
Go to: What is C-Peptide and Why Might it be Useful in Clinical Practice? C-peptide is a useful and widely used method of assessing pancreatic beta cell function [1, 2]. After cleavage of proinsulin, insulin and the 31-amino-acid peptide c-peptide are produced in equal amounts [3, 4]. So why is c-peptide testing preferable to insulin as a guide to beta cell function? The degradation rate of c-peptide in the body is slower than that of insulin (half-life of 20–30 min, compared with the half-life of insulin of just 3–5 min), which affords a more stable test window of fluctuating beta cell response. In healthy individuals the plasma concentration of c-peptide in the fasting state is 0.3–0.6 nmol/l, with a postprandial increase to 1–3 nmol/l . Half of all insulin secreted by the pancreas is metabolized in the liver by first-pass metabolism, whereas c-peptide has negligible hepatic clearance. C-peptide is cleared in the peripheral circulation at a constant rate, whereas insulin is cleared variably making direct measurement less consistent. In insulin-treated patients with diabetes, measurement of c-peptide also avoids the pitfall of cross-reaction of assay between exogenous and endogenous insulin. C-peptide is a cornerstone of the assessment of non-diabetes-associated hypoglycemia and the diagnosis of conditions such as insulinoma and factitious hypoglycemia but this area is beyond the scope of this article. Increasing evidence suggests that c-peptide may also be useful in predicting future levels of glycemic control, response to hypoglycemic agents, and risk of future diabetes complications. We will examine the key methods of sample collection for c-peptide determination and advise on what is most reliable and practical. Furthermore, we will summarize the clinica Continue reading >>
Insulin C-peptide Test
What is an insulin C-peptide test? Insulin is the hormone that is primarily responsible for lowering glucose levels in the blood, also called blood sugar. Insulin is produced by specialized cells in the pancreas called beta cells. When we eat, our bodies begin to break food down into glucose and other nutrients. In response, the pancreas produces insulin, which allows cells to absorb glucose from the blood. C-peptide is a byproduct created when insulin is produced. Measuring the amount of C-peptide in blood indicates how much insulin is being produced. Generally, high C-peptide production indicates high insulin production, and vice versa. The insulin C-peptide test is used to monitor insulin production in the body. The test can give doctors a lot of information about what is happening in your body. It can be used to: determine the cause of hypoglycemia, also called low blood sugar reveal how much insulin the pancreas is producing in a person newly diagnosed with type 1 diabetes distinguish between type 1 and type 2 diabetes, if the doctor is not sure which type of diabetes is present provide information about how well the beta cells in the pancreas are working The test may also be performed on patients who experience symptoms related to hypoglycemia in the absence of type 1 or type 2 diabetes. In this case, the body may be producing too much insulin. Symptoms of hypoglycemia include: sweating heart palpitations excessive hunger nervousness or irritability confusion blurred vision fainting seizures and/or loss of consciousness The preparation needed for the insulin C-peptide test depends on a person’s age and the reason for the test. In some instances, you may be required to fast for up to 12 hours before the test. Fasting requires that you to not eat or drink anything Continue reading >>
Interpreting Your C-peptide Values
Normal C-peptide levels for a fasting test are generally considered to be anything between 0.5 nanograms (ng) per millileter (ml) and 3 ng/ml, although people who do not have diabetes may occasionally stray out of this range. The following is a range of C-peptide values in people without diabetes, as compiled by Endocrine Sciences, Inc., a California-based laboratory that conducts the test. It should be noted that, in some cases, subjects fell below the normal range of C-peptide values, but were still not found to have diabetes. The range of values may also vary according to what lab your health care practitioner uses. Children (< 15 years old) 8:00 a.m. fasting: 0.4 to 2.2 ng/ml Adults 8:00 a.m. fasting: 0.4 to 2.1 ng/ml Two hours postprandial (after a meal): 1.2 to 3.4 ng/ml Two hours post glucose load: 2.0 to 4.5 ng/ml Although anything less than these numbers is generally an indicator of type 1 diabetes, values within the normal range can mean different things. “Type 2s with insulin resistance could actually be making more insulin than a non-diabetic slim person,” says Richard Bernstein, MD, FACE, FACN, CWS, of the Diabetes Center in Mamaroneck, New York. Values on the lower end may also indicate a honeymoon phase of type 1, when insulin production is slowing down but has not yet ground to a halt. Bernstein also points out that even in type 1s, a positive C-peptide test should be a source of optimism. “Of all my patients, I only have two who don’t make any C-peptide, and I’m one of them,” Bernstein says. He says this proves that most type 1s still produce at least some insulin and raises the possibility that therapies like beta-cell regeneration may eventually restore normal BG levels. This time of year, I always like to look back at the previous year an Continue reading >>
Blood Test: C-peptide
C-peptide, like the hormone insulin, is produced in the pancreas. Both are released simultaneously from the pancreas when the compound called proinsulin is split into two pieces. Insulin is responsible for regulating the body's glucose levels. Glucose, the body's main source of energy, is a sugar that comes from foods. After a meal, our bodies break down the foods we eat into glucose and other nutrients, which are then absorbed into the bloodstream from the gastrointestinal tract. Glucose levels in the blood rise after a meal and trigger the pancreas to make insulin and release it into the blood. When insulin is released, so is C-peptide. Insulin works like a key that opens the doors to cells and allows the glucose in. Without insulin, glucose can't get into the cells and it stays in the bloodstream. The most common cause of abnormal fluctuations in blood glucose is diabetes. C-peptide, on the other hand, has no effect on blood sugar. It is, however, useful as a marker of insulin production, since the pancreas typically releases C-peptide and insulin in about equal amounts. In general, high C-peptide levels are associated with increased insulin production, while low C-peptide levels indicate decreased insulin production. The C-peptide test may be ordered to determine how much insulin is being made by the pancreas. This information is useful because: It can help doctors tell the difference between type 1 and type 2 diabetes. In type 1 diabetes, the pancreas produces little or no insulin and little or no C-peptide. In type 2 diabetes, C-peptide levels will typically be normal or high, as the pancreas works harder to overcome insulin resistance (when the tissues become less sensitive to the effects of insulin) by producing more insulin. It can help find the cause of low b Continue reading >>
C-peptide Levels In Differentiation Of Type 1 And Type 2 Diabetes
C-peptide is a peptide composed of 31 amino acids released from the pancreatic beta-cells during cleavage of insulin from proinsulin preproinsulin, is produced in pancreatic beta-cells and is later cleaved to proinsulin and transported to the Golgi apparatus, where is packed into secretory granules during maturation of this granules, proinsulin is cleaved into 3 peptide chains - insulin (2 chains, A and B) and C-peptide C-peptide mainly excreted by the kidney half-life of C-peptide is 3-4 times longer than that of insulin amount of C-peptide in the blood can indicate the production or absence of endogenous insulin production abnormally low amounts of C-peptide in the blood suggest the insulin production is too low (or absent) because of type I diabetes C-peptide testing can help differentiate between factitious hypoglycemia due to exogenous insulin use (low C-peptide level, high insulin level) abnormally high amounts of C-peptide if hypoglycaemia warn of the possible presence of an insulinoma C-peptide measurement can be used to differentiate between insulin-dependent hypoglycemia (high C-peptide levels) versus insulin-independent hypoglycemia (low C-peptide levels) in a person with diabetes, a normal level of C-peptide indicates the body is making plenty of insulin but the body is just not responding properly to it - hallmark of type 2 diabetes (adult insulin-resistant diabetes) C-peptide can help differentiate between type 2 diabetes mellitus (normal C-peptide levels) and latent autoimmune diabetes of adults (LADA) (low C-peptide levels) Use of C-peptide in diagnosis of diabetes (1) do not measure C-peptide and/or diabetes-specific autoantibody titres routinely to confirm type 1 diabetes in adults consider further investigation in adults that involves measurement of C Continue reading >>
How Valuable Is Measurement Of C-peptide And Insulin Levels In Type 2 Diabetes?
Q:What is the rationale behind checking C-peptide and insulin levels? A:When insulin secretion by the pancreatic ß-cell is not sufficient to maintain normal blood glucose levels, diabetes develops. Although the exact cause of defective insulin secretion is not well-defined in type 2 diabetes, it is generally accepted that there is progressive ß-cell failure. The ß-cell produces proinsulin, which is then processed into C-peptide and insulin. C-peptide and insulin are released in equal concentrations in the blood. Therefore, C-peptide and insulin levels should be a marker for ß-cell function. Q:What are the pitfalls to testing C-peptide and insulin levels? A:C-peptide and insulin are produced at the same rate, but they are processed and eliminated by the body in different ways. After insulin is released from the pancreas, it undergoes significant first-pass clearance by the liver. Therefore, measuring peripheral levels of insulin is not a reliable indicator of insulin secretion by the pancreas. Also, either proinsulin or insulin antibodies can interfere with insulin assays. C-peptide is a more reliable indicator of insulin secretion because it is not cleared by the liver, it has a longer half-life than insulin (30 minutes compared to 4 minutes for insulin), and the pharmacokinetics of C-peptide have been well established in research studies.1 High glucose levels and renal failure can also affect blood levels of C-peptide and insulin. High glucose levels can cause glucose toxicity to the ß-cell and impair both C-peptide and insulin release.2 Renal failure, with a creatinine clearance of less than 50 mL/min, has been shown to increase fasting insulin levels by approximately 20% and fasting C-peptide levels increase by 100%.3 Q:Are there indications for the routine meas Continue reading >>
Serum C-peptide Concentrations Poorly Phenotype Type 2 Diabetic End-stage Renal Disease Patients - Sciencedirect
Volume 58, Issue 4 , October 2000, Pages 1742-1750 Clinical Nephrology Epidemiology Clinical Trials Serum C-peptide concentrations poorly phenotype type 2 diabetic end-stage renal disease patients Serum C-peptide concentrations poorly phenotype type 2 diabetic end-stage renal disease patients. A homogeneous patient population is necessary to identify genetic factors that regulate complex disease pathogenesis. In this study, we evaluated clinical and biochemical phenotyping criteria for type 2 diabetes in end-stage renal disease (ESRD) probands of families in which nephropathy is clustered. C-peptide concentrations accurately discriminate type 1 from type 2 diabetic patients with normal renal function, but have not been extensively evaluated in ESRD patients. We hypothesized that C-peptide concentrations may not accurately reflect insulin synthesis in ESRD subjects, since the kidney is the major site of C-peptide catabolism and would poorly correlate with accepted clinical criteria used to classify diabetics as types 1 and 2. Consenting diabetic ESRD patients (N = 341) from northeastern Ohio were enrolled. Clinical history was obtained by questionnaire, and predialysis blood samples were collected for C-peptide levels from subjects with at least one living diabetic sibling (N = 127, 48% males, 59% African Americans). Using clinical criteria, 79% of the study population were categorized as type 1 (10%) or type 2 diabetics (69%), while 21% of diabetic ESRD patients could not be classified. In contrast, 98% of the patients were classified as type 2 diabetics when stratified by C-peptide concentrations using criteria derived from the Diabetes Control and Complications Trial Research Group (DCCT) and UREMIDIAB studies. Categorization was concordant in only 70% of ESRD proban Continue reading >>
Does this test have other names? Connecting peptide insulin, insulin C-peptide, proinsulin C-peptide What is this test? This blood test looks at how well your body's makes insulin. It's used to help diagnose blood sugar disorders. Your body needs the hormone insulin to move sugar through your bloodstream to your cells for energy. A healthy pancreas makes equal amounts of insulin and the protein C-peptide. By measuring your C-peptide, your healthcare provider can also learn about your insulin level. Why do I need this test? Measuring C-peptide can show whether you have type 1 or type 2 diabetes. In type 1 diabetes, your body doesn't make any insulin. In type 2 diabetes, either your body doesn't make enough insulin or your cells can't use it normally. If you have diabetes, the C-peptide test can show how well your treatment is working. The C-peptide test may also be done to find the cause of low blood sugar. Or to check the activity of tumors that make insulin. What other tests might I have along with this test? Your healthcare provider also might order: Blood glucose test. This measures the amount of glucose (sugar) in your blood Glucagon test. This measures the level of another hormone made by the pancreas. Glucagon can increase blood sugar. A1c test. This is also known as glycosylated hemoglobin blood test. This is a measure of your blood glucose levels over the past 3 months. It shows how well your diabetes is being controlled. Insulin assay. This is a test that directly measures your insulin levels. What do my test results mean? Many things may affect your lab test results. These include the method each lab uses to do the test. Even if your test results are different from the normal value, you may not have a problem. To learn what the results mean for you, talk with Continue reading >>
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Persistence Of Prolonged C-peptide Production In Type 1 Diabetes As Measured With An Ultrasensitive C-peptide Assay
OBJECTIVE To examine persistence of C-peptide production by ultrasensitive assay years after onset of type 1 diabetes and factors associated with preserving β-cell function. RESEARCH DESIGN AND METHODS Serum C-peptide levels, a marker of insulin production and surviving β-cells, were measured in human subjects (n = 182) by ultrasensitive assay, as was β-cell functioning. Twenty-two times more sensitive than standard assays, this assay’s lower detection limit is 1.5 pmol/L. Disease duration, age at onset, age, sex, and autoantibody titers were analyzed by regression analysis to determine their relationship to C-peptide production. Another group of four patients was serially studied for up to 20 weeks to examine C-peptide levels and functioning. RESULTS The ultrasensitive assay detected C-peptide in 10% of individuals 31–40 years after disease onset and with percentages higher at shorter duration. Levels as low as 2.8 ± 1.1 pmol/L responded to hyperglycemia with increased C-peptide production, indicating residual β-cell functioning. Several other analyses showed that β-cells, whose C-peptide production was formerly undetectable, were capable of functioning. Multivariate analysis found disease duration (β = −2.721; P = 0.005) and level of zinc transporter 8 autoantibodies (β = 0.127; P = 0.015) significantly associated with C-peptide production. Unexpectedly, onset at >40 years of age was associated with low C-peptide production, despite short disease duration. CONCLUSIONS The ultrasensitive assay revealed that C-peptide production persists for decades after disease onset and remains functionally responsive. These findings suggest that patients with advanced disease, whose β-cell function was thought to have long ceased, may benefit from interventions to pre Continue reading >>