From the Guidelines
Insulin resistance (IR) is best diagnosed using a combination of clinical evaluation and laboratory tests, with the hyperinsulinemic-euglycemic clamp being the gold standard method for measuring IR, as it directly assesses the glucose disposal rate (GDR) 1.
Diagnostic Criteria
- The Fasting Insulin Test can be used, where a fasting insulin level above 10-15 μU/mL is indicative of insulin resistance.
- A Glucose-to-Insulin Ratio (GIR) can be calculated, where a ratio below 4.5 is suggestive of insulin resistance.
- The Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) index can also be used, with a value above 2.5 indicating insulin resistance.
- An Oral Glucose Tolerance Test (OGTT) can be performed, where a 2-hour glucose level above 140 mg/dL is indicative of impaired glucose tolerance, often associated with insulin resistance, as defined by the criteria for prediabetes 1.
Key Considerations
- It is essential to consult a healthcare professional for proper evaluation and interpretation of these tests.
- Medications such as metformin may be prescribed to help manage insulin resistance, typically starting with a dose of 500 mg once daily and gradually increasing to 1000-2000 mg per day, as needed and tolerated.
- Lifestyle modifications, including a healthy diet and regular exercise, are also crucial in managing insulin resistance.
- Insulin resistance is often associated with type 2 diabetes, which is characterized by a relative defect in glucose-stimulated insulin secretion, and can be improved with weight reduction, exercise, and/or pharmacologic treatment of hyperglycemia 1.
From the Research
Diagnostic Criteria for Insulin Resistance (IR)
The diagnostic criteria for insulin resistance (IR) involve various methods and indices to estimate insulin resistance. The most precise test is the hyperinsulinemic-euglycemic clamp, which examines the direct impact of insulin on glucose uptake by tissues 2. However, due to its complexity and intrusiveness, it is primarily utilized in research.
Diagnostic Methods
Some of the diagnostic methods for insulin resistance include:
- Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) and the Quantitative Insulin Sensitivity Check Index (QUICKI), which are based on measuring fasting glucose and insulin levels 2, 3
- Oral Glucose Tolerance Test (OGTT) and Insulin tolerance test 2
- Matsuda Index, which is suitable for clinical uses 3
- Hyperinsulinemic euglycemic clamp and intravenous glucose tolerance test, which are the most reliable methods available for estimating insulin resistance 3
Decision Rules for Insulin Resistance
Decision rules have been developed to identify insulin-resistant patients using routine clinical measurements, such as:
- BMI >28.9 kg/m(2), HOMA-IR >4.65, or BMI >27.5 kg/m(2) and HOMA-IR >3.60 4
- A score based on weighted combinations of fasting insulin, BMI, and fasting triglycerides 5
Surrogate Measurements of Insulin Sensitivity
Surrogate measurements of insulin sensitivity, such as fasting insulin, HOMA, insulin-to-glucose ratio, and Bennett index, have been compared to the euglycemic insulin clamp to determine their association with insulin sensitivity 5. The variables that best predict insulin sensitivity were found to be fasting insulin and fasting triglycerides 5.