Insulin Resistance Blood Test

Did you know insulin resistance is a precursor to prediabetes and type 2 diabetes? Being a precursor means insulin resistance comes before a prediabetes or type 2 diabetes diagnosis.

Despite the critical role of insulin resistance in metabolic health, it often goes undetected for years.

Early detection is essential, as insulin resistance can exist for up to a decade before progressing to prediabetes or type 2 diabetes, offering a critical window for intervention.

Strangely though, doctors do not routinely test for insulin resistance, so let’s chat about insulin resistance in more detail, and exactly how you can request an insulin resistance test so you fully understand your risk.

Even if you’re already living with prediabetes or type 2 diabetes, testing for insulin resistance can provide valuable insights to guide more effective treatment strategies, identify why challenges exist and help you improve long-term health outcomes.

What Is Insulin Resistance?

Insulin resistance occurs when the body’s cells become less responsive to insulin, a hormone produced by the pancreas that regulates blood sugar levels.

As a result of your cells being less responsive, the pancreas compensates by producing more insulin to maintain normal blood sugar levels.

Over time, this can lead to chronically elevated insulin levels (hyperinsulinemia), and eventually, prediabetes or type 2 diabetes.

Contrary to common belief, insulin resistance and prediabetes are not synonymous.

Prediabetes refers specifically to elevated blood glucose levels that are not yet high enough for a type 2 diabetes diagnosis.

Insulin resistance can exist independently of prediabetes, highlighting the importance of testing both insulin and glucose levels for a comprehensive assessment.

In people with prediabetes and type 2 diabetes, insulin resistance is the most common underlying cause.

Why Is Testing for Insulin Resistance Important?

Standard diagnostic tests for diabetes, such as fasting glucose or an oral glucose tolerance test, focus on blood sugar levels.

However, it is possible to have normal blood glucose levels while exhibiting significant insulin resistance.

Identifying insulin resistance early allows you to adopt lifestyle and nutrition interventions that can prevent or delay the onset of type 2 diabetes.

A case study illustrates this point: a patient with normal fasting glucose but a fasting insulin level of 16 mIU/L, indicating moderate to severe insulin resistance, was on a trajectory toward type 2 diabetes. With proper intervention, such trends can be reversed!

Blood Tests for Insulin Resistance

To assess insulin resistance, discuss the following blood tests with your doctor, which they will order via pathology:

1. Fasting Blood Glucose Test: Measures blood sugar levels after an overnight fast. Normal fasting glucose is typically less than 100 mg/dL (5.6 mmol/L). Elevated levels may indicate prediabetes or diabetes.
   • NOTE: In Canada, UK and Australia, normal fasting glucose is often set at 6.0 mmol/L.
2. Fasting Insulin Test: This test measures fasting insulin levels. Elevated fasting insulin can indicate insulin resistance, even when glucose levels are normal.
3. HOMA-IR (Homeostasis Model Assessment of Insulin Resistance): This calculation uses fasting glucose and insulin levels to estimate insulin resistance. It offers a more accurate assessment compared to using fasting insulin levels alone.
   • The formula is:
   • Glucose (mg/dl) x Insulin mIU/L // (divided by) 405
   • Glucose (mmol/l) x Insulin mIU/l // (divided by) 22.4
     • NOTE: You won’t have to calculate this formula yourself, as the result will usually be indicated on your pathology report.
4. HOMA-IR Insulin Resistance Test Range: There is no universally agreed-upon cut-off for HOMA-IR because “normal” values vary based on factors such as ethnicity, age, and obesity rates. However, general ranges used in research and clinical settings include:
   • HOMA-IR <2.0 is excellent
   • HOMA-IR 4.0 is average
   • HOMA-IR above 4.0 is cause for concern

Interpreting Fasting Insulin Test Results

While HOMA-IR provides a more detailed analysis, fasting insulin levels alone can offer insights into insulin resistance status.

There are two units that can be used to express insulin concentration, 1 μU/mL = 1 mIU/L. These are both the same, but the unit on your report may differ depending on your location.

• 10 mIU/L or lower: Ideal, good insulin sensitivity
• 11–14 mIU/L: Mild insulin resistance
• 14 mIU/L: Moderate insulin resistance
• Over 20 mIU/L: Abnormally high insulin levels, strong insulin resistance

It is important to note that while these tests are valuable, they should be interpreted within the broader context of your individual medical history and risk factors.

Risk Factors for Insulin Resistance

Several factors increase the risk of developing insulin resistance, including:

• Anthropometric Indicators:
  • Body mass index (BMI) >25
  • Waist circumference >40 inches or 101 cm (men) or >35 inches or 88 cm (women)
• Demographics:
  • Age >40 years
  • Certain ethnic backgrounds
• Health History:
  • Family history of type 2 diabetes or cardiovascular conditions
  • History of gestational diabetes or polycystic ovary syndrome (PCOS)
  • Acanthosis nigricans (darkened patches of skin)
• Metabolic Markers:
  • High blood pressure
  • Elevated triglycerides
  • Low HDL cholesterol

The Importance of Early Detection and Lifestyle Intervention

Detecting insulin resistance early allows you to implement lifestyle changes that can significantly reduce your risk of developing type 2 diabetes.

Evidence-based interventions include:

• Dietary Adjustments:
  A low-carbohydrate, nutrient-dense diet has been shown to improve insulin sensitivity and reduce fasting insulin levels.
• Physical Activity:
  Regular exercise, including resistance and aerobic training, enhances insulin sensitivity by improving glucose uptake in muscle tissue.
• Weight Management:
  Reducing visceral fat (the fat around the belly/midsection) is critical, as abdominal obesity is closely linked to insulin resistance.
• Stress Reduction and Sleep:
  Chronic stress and poor sleep can worsen insulin resistance. Strategies such as mindfulness meditation and prioritizing sleep are beneficial.

The Value of Testing Insulin Resistance in Prediabetes and Type 2 Diabetes

Testing for insulin resistance is particularly valuable, even when you already have prediabetes or type 2 diabetes.

For those with prediabetes, identifying your level of insulin resistance provides an opportunity to intervene before blood sugar levels escalate further.

It allows for targeted lifestyle changes, such as dietary adjustments, increased physical activity, and weight management, that can help you reverse prediabetes.

For those with type 2 diabetes, understanding insulin resistance can help tailor your treatment strategy.

For example, if you know your insulin resistance level is moderate-to-high, you can focus on strategies that improve insulin sensitivity, rather than solely addressing blood sugar levels.

Regular monitoring of insulin resistance can also provide valuable feedback on the effectiveness of any strategies you put in place, ensuring that the focus remains on addressing the root cause of the condition rather than just its symptoms.

Next time you visit your doctor for an A1c test, request a fasting insulin test as well.

Conclusion

Insulin resistance is an invisible but reversible condition that often precedes prediabetes and type 2 diabetes, often by years.

Testing for insulin resistance, including fasting glucose, fasting insulin, and HOMA-IR, provides a comprehensive view of metabolic health.

Testing fasting insulin is incredibly important to assess insulin resistance, but it’s a test the doctor doesn’t usually test for, so be sure to ask for it.

By understanding your risk and taking proactive steps, you can significantly reduce your risk of developing prediabetes or type 2 diabetes.

Early detection empowers you to take control of your health, making insulin resistance testing an invaluable tool in preventive healthcare, and ensuring you maintain optimal health, over the long term.