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This article waslast modified on March 4, 2020.
What is insulin resistance?

Insulin resistance is a condition in which the cells in your body don't respond as well to the hormone insulin. Insulin is produced by the pancreas and is important for the transportation, use and storage of glucose, the body's usual main source of energy. Insulin regulates the transport of glucose into skeletal muscles, fat tissue and the liver, where glucose is needed for energy production.

  • Normally, after a meal, the carbohydrates that you eat are broken down into glucose and other simple sugars that are absorbed by the intestine.
  • This causes blood glucose levels to rise and stimulates the pancreas to release insulin into the bloodstream.
  • The amount of insulin released corresponds to the size and content of the meal.
  • Insulin helps transport glucose into the body's cells, where it is used for energy.
  • As glucose moves into the cells and is broken down (metabolized), the blood glucose level drops and the pancreas responds by decreasing the release of insulin.
  • Insulin works together with glucagon, another pancreatic hormone, to maintain blood glucose levels within a narrow range.

If your body's cells are less sensitive to insulin, then less glucose is transported from the blood into cells.

  • Blood glucose levels remain high but your cells "starve."
  • Your pancreas compensates by producing more insulin to try to move more glucose into cells.
  • In most cases, your pancreas is able to keep pace with the need for extra insulin for many years. Most people with insulin resistance do not develop diabetes.
  • In some cases, the pancreas eventually can't keep up with demand and blood glucose continues to rise, causing type 2 diabetes.

The cause of insulin resistance is not fully understood. Experts think that major contributing factors are being overweight, especially having excess belly fat, and not getting enough exercise. The condition is also thought to be due partly to genetic factors and ethnicity.

Insulin resistance is the main feature of the "metabolic syndrome." The metabolic syndrome is described as a set of features that link excess fat around the waist (abdominal obesity) and insulin resistance to increased risk of cardiovascular disease, as well as other problems, such as stroke. Obesity also increases risk of various cancers.

Features of the metabolic syndrome include:

  1. Elevated blood glucose
  2. An elevated triglyceride level
  3. Low levels of high density lipoprotein (HDL) cholesterol
  4. High blood pressure

Note that not everyone with metabolic syndrome will necessarily have all four of these features. (For additional details, see the article on Metabolic Syndrome.)

Accordion Title
About Insulin Resistance
  • Complications

    Over time and left untreated, insulin resistance can lead to other serious conditions. The harmful effects of insulin resistance result from:

    • The consequences of elevated blood insulin itself (as the body attempts to compensate for reduced insulin action)
    • The inadequate effects of insulin despite an increase in blood insulin levels

    Elevated blood insulin levels over time can have harmful effects, such as:

    • Hardening of the arteries (atherosclerosis)—studies have shown a strong association between atherosclerosis and elevated insulin, but it is unclear whether elevated insulin itself cause atherosclerosis.
    • High blood pressure
    • Increased risk of blood clots in the arteries
    • Elevated blood uric acid levels, which can cause gout, a classic symptom of the metabolic syndrome
    • Increased male hormones (androgens)—women with the metabolic syndrome may have excess facial and body hair, loss of hair from the top of their head (balding), deepening of the voice, and often suffer from the polycystic ovary syndrome (PCOS). PCOS can cause irregular menstrual periods, no menstrual periods and/or infertility.
    • Darkened patches of skin or skin tags (acanthosis nigricans)—can occur where skin rubs on the skin, such as in the neck, groin, arm pits, and, in women, under the breasts. In serious cases, increased pigmentation can be seen on the cheeks and face.

    Many of these factors (e.g., hypertension, increased blood coagulation, increased uric acid, and increased androgens) promote the development and progression of atherosclerosis.

    When your body's cells are less responsive to insulin (despite an elevated blood insulin level), you may have:

    • Elevated blood glucose—high blood sugar (glucose) can have serious long-term consequences, such as kidney disease, nerve damage, and heart disease. Mild elevations in blood glucose are described as "prediabetes." If you have symptoms of diabetes (e.g., increased urination, increased thirst, weight loss, blurry vision, etc.), and your glucose or A1c is elevated above certain thresholds, you are diagnosed with diabetes. If you have no symptoms, elevated glucose must be confirmed on two separate days to diagnose diabetes. Alternatively, 2 abnormal glucose or A1c levels on the same day can diagnose diabetes in an asymptomatic person.
    • Abnormal lipid levels—these include low HDL cholesterol (the "good" cholesterol), increased LDL cholesterol (the "bad" cholesterol), elevated triglyceride levels and "dense" LDL particles where the particles have a reduced cholesterol content. Unhealthy lipid levels can increase your risk of cardiovascular disease. Elevated triglyceride levels are associated with an increased fat content in the liver, causing non-alcoholic fatty liver (NAFL). If the metabolic syndrome is untreated, liver inflammation can result, producing NAFL. If inflammation develops, NAFL progresses to "non-alcoholic steatohepatitis" (NASH). Steatohepatitis is the combination of increased liver tissue fat (“steatosis”) and inflammation ("hepatitis"). NASH can lead to liver cirrhosis, liver failure or even liver cancer (e.g., hepatocellular carcinoma).

    While about 25% of adult Americans have the metabolic syndrome, insulin resistance can first develop in childhood and cause disease before adulthood. Approximately 6% to 39% of overweight or obese teens have the metabolic syndrome. Such children, even less than 10 years old, can have type 2 diabetes, elevated triglycerides, low HDL cholesterol, high blood pressure, elevated uric acid, acanthosis nigricans and, in teen girls, PCOS.

  • Tests

    There is no single test that can directly diagnose insulin resistance. Instead, your healthcare practitioner will consider several factors, including medical history, physical exam, signs and symptoms as well as test results.

    Laboratory testing may include:

    • Glucose—a fasting plasma glucose (FPG) or a glucose tolerance test (GTT) may be used to screen for, diagnose and monitor prediabetes or diabetes.
    • Hemoglobin A1c (A1c)—this test measures A1c to determine your average blood glucose levels over the past 2 to 3 months. It may also be used to screen for, diagnose and monitor prediabetes and diabetes.
    • Lipid panel—a group of tests that measure specific lipids in the blood (i.e., total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides). Usually the LDL cholesterol level is calculated. If the triglycerides are significantly elevated (e.g., greater than 400 mg/dL), LDL cholesterol should not be calculated and a direct LDL (direct measurement of the LDL cholesterol) can be performed.

    Other laboratory tests may be ordered to help detect conditions associated with insulin resistance. Examples include:

    • High-sensitivity CRP (hs-CRP)—measurements can detect low levels of inflammation and may be done as part of an evaluation of cardiac risk. CRP may be increased with insulin resistance.
    • Alanine aminotransferase (ALT)—non-alcoholic fatty liver disease (NAFL) is very common in people with metabolic syndrome. Elevated ALT levels suggest liver damage. However, this test may not be very sensitive in detecting NAFL. It is not considered a routine test in the evaluation of persons with the metabolic syndrome. Ultrasound scans are more sensitive for the detection of NAFL than ALT measurements.
    • Uric acid—may be elevated with gout.
    • Testosterone—may be used to measure levels in women with PCOS or signs and symptoms of excess androgens. If sex hormone binding globulin (SHBG) is measured, free testosterone can be calculated. Free testosterone is the biologically active testosterone. If the total testosterone is no clearly elevated or only borderline elevated in a woman with hirsutism, free testosterone should be calculated.
    • Insulin—The fasting insulin level can be measured. Insulin levels will usually be elevated in those with significant insulin resistance. However, this test is rarely needed and is not recommended in routine clinical practice.
  • Treatment

    Both children and adults can develop insulin resistance and the metabolic syndrome. The best approach to the prevention of the metabolic syndrome is the prevention of obesity.

    Treatment of insulin resistance (and improving insulin sensitivity) primarily involves making changes in your diet and lifestyle. The American Diabetes Association recommends losing excess weight, getting regular amounts of moderate-intensity physical activity, and eating a healthy diet. Over time, these steps can:

    You should work with your healthcare practitioner and with other medical professionals, such as a nutritionist, to develop an individualized treatment plan and to monitor how well it works for you.

    Medications may also be necessary to treat co-existing conditions or diseases. Some examples include:

    • Blood pressure medication
    • Metformin for diabetes
    • Statins to lower LDL cholesterol
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Christine L. Snozek, PhD. Lab Tests Online adjunct board member.