Insulin
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- Also Known As:
- Fasting Insulin
- Formal Name:
- Insulin
- serum

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At a Glance
Why Get Tested?
To help evaluate insulin production by the beta cells in the pancreas; to help diagnose the presence of an insulin-producing tumor in the islet cells of the pancreas (insulinoma); to help determine the cause of low blood glucose (hypoglycemia); to help identify insulin resistance, or to help determine when a type 2 diabetic might need to start taking insulin to supplement oral medications
When To Get Tested?
When you have low blood glucose levels with symptoms such as sweating, palpitations, dizziness, fainting; when you have diabetes and your health care practitioner wants to monitor your insulin production; sometimes when it is suspected that you have insulin resistance
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
Typically, you will be asked to fast for 8 hours before the blood sample is collected. Occasionally, a health care practitioner may do testing when fasting is not possible, such as when a glucose tolerance test is done. In some cases, a health practitioner may request that you fast longer than 8 hours.
You may be able to find your test results on your laboratory’s website or patient portal. However, you are currently at Testing.com. You may have been directed here by your lab’s website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab’s website or portal, or contact your healthcare practitioner in order to obtain your test results.
Testing.com is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.
The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.
If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.
Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called “normal” values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.
While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are “within normal limits.”
For more information, please read the article Reference Ranges and What They Mean.
What is being tested?
Insulin is a hormone that is produced and stored in the beta cells of the pancreas. It is secreted in response to elevated blood glucose following a meal and is vital for the transportation and storage of glucose, the body’s main source of energy. Insulin helps transport glucose from the blood to within cells, thus helping regulate blood glucose levels, and has a role in lipid metabolism. This test measures the amount of insulin in the blood.
Insulin and glucose blood levels must be in balance. After a meal, carbohydrates usually are broken down into glucose and other simple sugars. These are absorbed into the blood, causing the blood glucose level to rise, which in turn stimulates the pancreas to release insulin into the blood. As glucose moves into cells, the level in the blood decreases and release of insulin by the pancreas decreases.
If an individual is not able to produce enough insulin, or if the body’s cells are resistant to its effects (insulin resistance), glucose cannot reach most of the body’s cells and the cells starve. Meanwhile, blood glucose rises to an unhealthy level. This can cause disturbances in normal metabolic processes that result in various disorders and complications, including kidney disease, cardiovascular disease, and vision and neurological problems.
Diabetes, a disorder associated with high glucose levels and decreased insulin effects, can be a life-threatening condition. People with type 1 diabetes produce very little insulin and so eventually require insulin supplementation therapy. Type 2 diabetes is generally related to insulin resistance, which increases with time.
With insulin resistance, many of the body’s cells are unable to respond to the effects of insulin, leaving glucose in the blood. The body compensates by producing additional amounts of the hormone. This results in a high level of insulin in the blood (hyperinsulinemia) and over-stimulation of some tissues that have remained insulin-sensitive. Over time, this process causes an imbalance in the relationship between glucose and insulin and, without treatment, may eventually cause health complications affecting various parts of the body.
In addition to type 2 diabetes, insulin resistance may be seen in those with polycystic ovary syndrome (PCOS), prediabetes or heart disease, metabolic syndrome, acanthosis nigricans, and with disorders related to the pituitary or adrenal glands.
Other than in insulin resistance, hyperinsulinemia is most often seen in people with tumor of the islet cells in the pancreas (insulinomas) or with an excess amount of administered (exogenous) insulin. Hyperinsulinemia causes low blood sugar (hypoglycemia), which can lead to sweating, palpitations, hunger, confusion, blurred vision, dizziness, fainting, and seizures. Since the brain is dependent on blood glucose as an energy source, severe glucose deprivation due to hyperinsulinemia can lead fairly quickly to insulin shock and death.
Common Questions
View Sources
Sources Used in Current Review
2017 review performed by Alan F. Weir, PhD, DABCC, Instructor, Fox Valley Technical College.
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(November 2016) Insulin, Medicines, and other Diabetes Treatments. Available online at https://www.niddk.nih.gov/health-information/diabetes/overview/insulin-medicines-treatments. Accessed 6/9/2017.
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