Insulin C-peptide test, also known as Proinsulin C peptide, C-peptide or Connecting peptide insulin, is one of the many different types of blood tests, which are relevant, in case of diabetics or those dealing with metabolic syndrome. This particular blood test evaluates the exact amount of C-peptide present in the bloodstream.
Information On C-Peptide
The connecting peptide is essentially constituted by amino acids which connect the ‘A and ‘B’ chains of insulin. C-peptide is released as an offshoot of insulin formation by an organ called pancreas. As pancreas forms insulin, it simultaneously secretes C-peptide into the blood. Although C-peptide has no effect on the blood sugar level, this substance works as a steady biomarker of insulin production as it has a tendency to stay in the blood for a longer span as compared to insulin.
Need For a C-Peptide Test
This diagnostic type of blood test is ordered for by a doctor for any of the given reasons.
If an individual has been recently diagnosed with diabetes, a connecting peptide test may be required to ascertain whether that person is suffering from type1 (insulin dependent) or type2 (non-insulin resistant) diabetes. If the pancreas are not secreting any insulin then blood examination will present an abnormally low level of both, insulin and C-peptide. In short, this particular test enables the doctor to identify whether the affected person has type1 or type 2 diabetes.
This test is ordered when the cause of lowered level of blood sugar, also called hypoglycemia needs to be found out. The reason could be either linked to the presence of insulinoma or an overuse of blood glucose lowering medicines. The C peptide test aids in monitoring the amount of insulin production post-removal of insulinoma, a non cancerous pancreatic tumour. The tumor growth overstimulates the pancreas to release excessive amounts of insulin resulting in an elevated level of C-peptide in the bloodstream. Therefore, this test is carried out to verify whether or not the tumour has been thoroughly ousted.
How To Prepare For C-Peptide Test
Your doctor will give you the full set of instructions to be followed before undergoing the test. These proceed as follows-
To undertake the C peptide test for diabetes, one needs to refrain from eating and drinking for a minimum of eight hours prior to the blood test. In case you are concurrently on oral medications or insulin, you must stop taking the drugs till the test is done.
How Is C-Peptide Test Done
To gauge the level of C-peptide in the blood, a blood sample needs to be drawn. A clean elastic band will be wrapped around the upper half of your arm in order to temporarily halt the flow of blood. This, in turn, makes the veins in the lower aspect of the arm larger. As a result, needle insertion in the vein becomes easy.
Once the skin where the needle is to be pierced is swabbed using alcohol, a sterile needle stick (sometimes more than one) is introduced in the vein. A tube attached to the needlestick collects the blood sample. The entire test thus involves an uncomplicated needle prick or pinch and takes nothing more than a minute.
It is possible that a small sized bruise forms at the site of needle insertion. However, this can be avoided by placing an apt pressure on the site for a few minutes.
Although quite rare, the vein from which blood is drawn may swell up post the test. This type of swelling is called phlebitis.
Stimulated C-Peptide Test
In case the blood test is being done to distinguish between type 1 or type 2 diabetes, an additional injection of glucagon maybe administered into your arm amidst two separate blood samples. This is done to stimulate the production of insulin.
Interpretation Of the C-Peptide Test Result
If the level of C-peptide in the blood varies somewhere between 0.51 to 2.72 nanograms per millilitre (ng/mL), there is no cause for worry. However, an elevated level of C-peptide usually points towards raised levels of autogenous insulin formation. This may occur either in relation to high amounts of blood sugar caused by too much of sugar intake and/or development of resistance towards insulin. Some of the other possible reasons for high levels of C-peptide in the bloodstream include Cushing’s syndrome, kidney failure or hypokalemia.
This type of reading can also be seen in cases of pregnancy or tumours such as insulinomas. On the other hand, low levels of C-peptide are linked with decreased level of insulin. This occurs due to an insufficient production of insulin by the pancreatic beta cells. Thus, drop in the level of C-peptide and raised blood sugar level could be indicative of Type 1 diabetes.