What is Insulin & Fasting Insulin?
Key Takeaways
Insulin is a hormone that’s crucial for regulating blood sugar levels.
The pancreas releases insulin in response to a rise in blood sugar levels, which usually occurs after eating.
Insulin causes cells to take up glucose from the blood, and either use it or store the extra energy in the form of fat or glycogen.
Insulin resistance occurs when the body’s cells are not able to respond to insulin normally.
Insulin resistance leads to high insulin levels, as the pancreas releases extra insulin to try and compensate.
A fasting insulin test paired with a fasting glucose (sugar) test can detect issues with your metabolic health, such as insulin resistance.
Other tests of metabolic health, such as an oral glucose tolerance test or hemoglobin A1c test, may be used along with fasting glucose and fasting insulin to gain a complete picture of your metabolic health.
Metabolic health is important for longevity and long-term well-being.
What is Insulin?
Insulin is a hormone that’s crucial for regulating blood sugar levels. This hormone is produced by the pancreas, a gland which is located in the back of the abdomen.
In people with diabetes or prediabetes, the body either doesn’t make enough insulin (seen in Type 1 Diabetes Mellitus) or it doesn’t respond normally to insulin (seen in Type 2 Diabetes Mellitus). This causes blood sugar levels to be higher than normal. High blood sugar causes a variety of health complications by damaging blood vessels and tissues, and can significantly shorten a person’s lifespan and healthspan (the number of years that they spend enjoying good health).
If you’re interested in longevity and healthy aging, it’s essential to know how your body is producing and responding to insulin. A fasting insulin test paired with a fasting glucose test can provide important information that helps you to optimize your lifestyle and address any issues early, before health complications arise. This article will examine the role of insulin in your health and how you can interpret the results of your insulin test.
What Does Insulin Do?
Insulin is secreted in response to a rising blood sugar level. After you eat a meal, the carbohydrates in your food will be absorbed into your bloodstream, and your blood sugar levels begin to rise. Certain cells in your pancreas, known as beta cells, detect the increase in blood sugar and release insulin.
In general, insulin is a signal to cells throughout the body that there’s plenty of energy available. It’s known as an anabolic hormone, meaning that it triggers cells to build structures and store energy for later use.
Insulin causes cells throughout the body to take up glucose from the blood. Cells can break down the glucose for energy and use that for maintenance and repair processes, or they can store the energy for later. Some cells, like liver and muscle cells, can store glucose directly in the form of a starch known as glycogen. This allows for very quick release of glucose later, such as during exercise.
Excess energy can also be stored in the form of fat, and insulin causes cells to create and store fat. It also stimulates cells to produce more proteins, which can be functionally useful for the cell and also serve a storage function, because they can later be broken down into their component parts (known as amino acids) if needed.
Insulin also inhibits the breakdown of fats and proteins in the body. This is because insulin is released when the body senses there is a surplus of energy, so there is no need to use up the body’s store of energy in the form of fats and proteins. Because of this, high insulin levels make weight loss more difficult., They prevent cells from breaking down excess fat that they’ve previously stored.
Recommended Reading: Reducing Insulin Resistance for Weight Loss
Insulin Resistance
In order for insulin to have its effects, cells in the body need to respond to insulin. This is known as insulin sensitivity. In a person with normal insulin sensitivity, when insulin is released from the pancreas into the bloodstream, cells throughout the body will respond to insulin by taking up blood glucose (sugar) and building up their glycogen, fat, and protein stores.
Reduced insulin sensitivity is known as insulin resistance. In a person who’s experiencing insulin resistance, cells throughout the body don’t respond normally to insulin. This is more evident after a meal, when the pancreas releases insulin, but cells do not respond by taking up glucose effectively, resulting in excess glucose remaining in the bloodstream, which can cause damage to the blood vessels and tissues throughout the body.
When the body is resistant to the effects of insulin, the pancreas secretes extra insulin in an attempt to compensate for the insulin resistance in order to lower blood glucose. A person experiencing insulin resistance will therefore have higher levels of insulin in their blood than a person who has normal insulin sensitivity.
The Correlation Between Insulin Resistance and Longevity
When insulin resistance becomes more severe, the body is no longer able to compensate by getting the pancreas to increase insulin production, eventually resulting in rising blood glucose (sugar). When the blood glucose rises, it can eventually reach pre-diabetes and type 2 diabetes mellitus ranges. High blood glucose as part of pre-diabetes and type 2 diabetes mellitus increases the risk of many conditions that can shorten a person’s lifespan or healthspan, and is believed to be a major factor in the aging process.
For example, high blood glucose increases the risk of developing cardiovascular disease (such as ischaemic heart disease and ischaemic stroke). Higher levels of blood glucose damages the lining of blood vessels throughout the body. This makes it easier for cholesterol to deposit into the walls of the arteries, which in turn reduces blood flow and can lead to a heart attack or a stroke. High blood glucose levels also affect the expression of certain genes, which causes increases in triglyceride and LDL cholesterol levels, which in itself also increases risk of cardiovascular disease.
Recommended Reading: Heart Health and Longevity
As people age, insulin resistance becomes more common. However, centenarians (people who live to age 100) are more likely to maintain relatively normal insulin sensitivity through good lifestyle practices and genetics. In general, keeping blood glucose levels in a normal range will help to prevent health complications, leading to greater longevity and better quality of life. If you are at risk of developing insulin resistance, detecting this early and taking steps to help restore your insulin sensitivity will improve your chances of living a long and healthy life.
Insulin Testing
There are several different types of tests that may be used to assess the body’s insulin response. Different tests may be used in different situations, depending on your risk factors, symptoms, and family history.
Fasting Insulin
Your fasting insulin level is the level of this hormone in your blood when you have not recently consumed any food. This gives a measurement of your baseline insulin level.
For a fasting insulin test, you’ll need to go to the lab for a blood draw when you haven’t eaten in the past 8 to 12 hours. In most cases, this means having your blood drawn first thing in the morning, before you take your breakfast.
In general, a normal fasting insulin level should be less than 25 mIU/L (174 pmol/L). A level higher than this would be considered a high fasting insulin level. While a very low fasting insulin level may also indicate a medical issue, there’s no consensus on exactly what level of fasting insulin should be considered too low.
This fasting insulin level needs to be paired with a fasting blood glucose test in order to assess the severity of insulin resistance.
It’s important to have a qualified physician interpret the results of your fasting insulin and fasting glucose tests. Your doctor will discuss your test results with you, and will let you know if they’re concerned about your fasting insulin level.
Low Insulin Levels
Low fasting insulin levels generally indicate that the pancreas is not able to produce enough insulin. This may be caused by:
Type 1 diabetes, a condition in which the immune system mistakenly begins to attack the beta cells in the pancreas that produce insulin
Type 2 diabetes in its late stage, when the pancreas has lost the ability to make enough insulin after many years
Other conditions that affect the pancreas, such as pancreatitis or pancreatic cancer
When the pancreas is not able to make enough insulin, the body can’t process glucose properly. It builds up in the blood, potentially leading to very high blood sugar levels. In extreme cases, this can lead to a life-threatening condition known as diabetic ketoacidosis. At the same time, because the cells aren’t able to take up sugar from the blood, the body must burn its stores of fat for energy, leading to ketone overaccumulation in the blood, causing a medical emergency due to increased blood acidity from high ketone levels.
Insulin Resistance
When the body is insulin resistant, then the pancreas releases extra insulin in an attempt to compensate, and fasting insulin levels will be high for the corresponding fasting blood sugar level. Insulin resistance may be caused by:
Obesity
Physical inactivity
Chronically high stress levels
Hormonal conditions, such as acromegaly (high growth hormone levels) or Cushing’s syndrome (high cortisol levels)
Certain medications, such as prednisone or other corticosteroids
Insulin resistance results in high insulin levels which promote fat storage, which tends to lead to weight gain. As insulin resistance becomes more severe, type 2 diabetes may develop. Blood sugar levels start to rise, which increases the risk of a variety of health problems, including heart disease, kidney disease, and vision loss.
Insulin resistance is also associated with polycystic ovary syndrome (PCOS), a condition that can present with menses irregularity, high testosterone features such as acne and excessive hair growth, and polycystic ovaries.
Blood Glucose Testing
The body’s insulin resistance can also be assessed by testing blood sugar levels. These tests help to provide a more complete picture of insulin’s action within your body. Specific tests may include:
Fasting glucose (sugar). This test checks your blood sugar level when you haven’t eaten for 8 to 12 hours. A high fasting glucose level could help to diagnose pre-diabetes and type 2 diabetes mellitus resulting from high insulin resistance.
Homeostatic Model Assessment for Insulin Resistance (HOMA-IR). For this test, both your insulin and blood glucose (sugar) levels are tested while you’re fasting. By comparing these two levels, the test can determine whether your body’s insulin response is proportional to your glucose level, thus assessing the severity of insulin resistance. A high HOMA-IR score indicates insulin resistance.
Oral glucose tolerance test (OGTT). For this test, your fasting glucose level will first be measured. You then drink a beverage containing a measured 75g of glucose, and your glucose level is checked again at specific time points afterwards. This is able to assess whether your body is able to bring down your blood glucose after drinking a sugar load, which can help to diagnose pre-diabetes and type 2 diabetes mellitus.
Hemoglobin A1c (HbA1c). This test is used to measure your average blood glucose level over the previous three months. A high HbA1c level can help to assess your blood glucose control over the last 3 months and diagnose pre-diabetes and type 2 diabetes mellitus.
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Managing Insulin Resistance
Lifestyle Modifications
The first step in addressing insulin resistance is through lifestyle changes focused on weight reduction and increasing physical activity. There are several effective actions that have been shown to help improve insulin sensitivity, including:
A healthy diet. Weight reduction, which improves insulin sensitivity, is key. A diet high in whole foods such as fruits, vegetables, nuts and whole grains, and low in fat can help in weight reduction which can reduce insulin resistance.
Exercise. There is strong evidence that physical activity helps to maintain the body’s insulin sensitivity. Both aerobic exercise and resistance training can help to improve insulin sensitivity, beyond just weight loss alone. Aerobic exercise is the type that gets your heart pumping faster and makes you breathe harder, such as brisk walking, running, dancing, cycling, or swimming. Resistance training can involve weight training, pulling on resistance bands, or body weight exercises.
Weight management. Obesity is strongly associated with insulin resistance, because fat tissue interfere with insulin signaling in the body. Taking steps towards a healthier body weight will help to restore your body’s insulin sensitivity. This involves lifestyle modifications via a healthy diet and increased exercise as mentioned above. For certain patients, weight loss medications such as GLP-1 RAs are also able to help with weight management if lifestyle modifications are insufficient.
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In order for lifestyle changes to benefit your health, you’ll need to maintain them over the long term. That’s why it’s important to ensure that your changes are sustainable and fit in well with other parts of your life. Our NOVI Health clients receive support from health coaches, to help you develop a healthy lifestyle plan that will work well for you – and to stick to it.
Medical Interventions
If lifestyle changes are not insufficient to improve insulin resistance, or if blood glucose has risen to pre-diabetes or type 2 diabetes mellitus levels, it is important to speak to your doctor for further diagnosis and management of your condition, with lifestyle and medications if necessary.
Insulin in Overall Health
Research has shown that insulin sensitivity and insulin resistance are important markers of metabolic health, and that maintaining the body’s insulin sensitivity is important for longevity. To give yourself the best chance of living a long and healthy life, knowing your insulin sensitivity and insulin resistance is one way to assess your current metabolic health.
If you discover that you have insulin resistance, you can take steps to help improve your insulin sensitivity and protect your long-term health and well-being. You’ll need to talk with a physician to develop a personalized plan for this. A health coach can also help you to create and stick with your own healthy lifestyle system. All of our NOVI Health clients receive help from expert physicians and health coaches.
Metabolic health is just one aspect of your overall wellness. To fully understand your health and detect the potential threats to your longevity, you’ll need to consider a variety of other aspects of your health as well. NOVI Assessment Max has been carefully developed with a complete testing panel, which allows you to get a comprehensive picture of your overall well-being. By detecting any potential issues as early as possible, you’ll be able to develop an informed plan that helps to address these problems and improve your health, your energy levels, and your overall well-being.