How to Test for Insulin Resistance: Functional and Clinical Approaches

What Is Insulin Resistance and Why Test for It?

Insulin resistance occurs when your body’s cells become less responsive to insulin — the hormone that moves glucose (sugar) out of the bloodstream and into the cells for energy. To compensate, the pancreas produces more insulin, leading to elevated insulin levels long before blood sugar becomes abnormal.

Over time, this imbalance can contribute to:

• Fatigue and energy crashes after meals

• Weight gain, especially around the abdomen

• Increased hunger and sugar cravings

• Elevated triglycerides or low HDL

• Hormonal imbalance (especially in PCOS)

• Higher risk of metabolic syndrome, prediabetes, and cardiovascular disease

Early testing helps identify insulin resistance before it progresses to more serious metabolic conditions.

Signs and Risk Factors for Insulin Resistance

You might consider testing for insulin resistance if you experience symptoms such as:

• Fatigue or “brain fog” after eating

• Difficulty losing weight

• Sugar cravings or shakiness between meals

• Acne or oily skin

• Irregular menstrual cycles (in women)

Risk factors include:

• Family history of diabetes or PCOS

• Overweight or obesity (especially central fat)

• Sedentary lifestyle

• Poor sleep or chronic stress

• History of gestational diabetes or elevated fasting glucose

Many individuals with insulin resistance still have “normal” blood glucose results — making insulin testing a crucial early screening tool.

Laboratory and Functional Tests for Insulin Resistance

There are several ways to evaluate how well your body regulates glucose and insulin. A naturopathic or functional medicine approach often combines multiple markers for a more clear picture.

Fasting Glucose and HbA1c

• Fasting glucose measures your blood sugar after 8–12 hours without eating.

  • Normal: <5.6 mmol/L (100 mg/dL)

  • Prediabetes: 5.6–6.9 mmol/L (100–125 mg/dL)

• HbA1c reflects your average blood sugar over 2–3 months.

  • Normal: <5.7%

  • Prediabetes: 5.7–6.4%

These are helpful starting points, but insulin resistance can be present even when both are normal.

Fasting Insulin

Measuring fasting insulin alongside glucose provides early insight into how hard your pancreas is working to maintain normal glucose levels.

• Normal: ~14–56 pmol/L

• Mild elevation: ~63–97 pmol/L (possible early insulin resistance)

• High: >104 pmol/L (often significant insulin resistance)

Even mildly elevated fasting insulin can indicate your body is compensating long before blood sugar rises.

HOMA-IR (Homeostatic Model Assessment of Insulin Resistance)

The HOMA-IR score combines fasting glucose and insulin to estimate insulin sensitivity.

• Optimal: <1.5

• Mild insulin resistance: 1.5–2.9

• Significant resistance: ≥3.0

This simple calculation can be performed from standard blood tests, offering a more sensitive marker than glucose alone.

Oral Glucose Tolerance Test (OGTT) with Insulin

The OGTT involves drinking a glucose solution after fasting, followed by blood draws at 30, 60, and 120 minutes.

When insulin levels are measured alongside glucose, this test can uncover patterns of hyperinsulinemia — even when glucose levels remain in range.

An early insulin spike or sustained elevation suggests insulin resistance and reduced glucose uptake by cells.

Continuous Glucose Monitoring (CGM)

A CGM is a small wearable sensor that measures glucose every few minutes throughout the day.
It helps identify:

• Post-meal spikes

• Overnight fluctuations

• Individual food responses

CGMs are especially useful for those with metabolic syndrome, PCOS, or hypoglycemia symptoms.

Advanced and Functional Markers

Additional tests that can support insulin resistance assessment include:

• Lipid profile: elevated triglycerides and low HDL

• hs-CRP: inflammation often associated with metabolic dysfunction

• Lipoprotein Insulin Resistance Index (LP-IR): advanced NMR analysis of lipoprotein particle size and insulin sensitivity

• METS-IR or QUICKI indices: emerging tools to assess insulin resistance without direct insulin measurement

Interpreting Results: What Patterns Reveal

Your lab values are best interpreted as a pattern rather than in isolation.

• Normal glucose + high insulin: early insulin resistance

• Elevated glucose + high insulin: progressing insulin resistance

• Elevated glucose + low insulin: pancreatic insufficiency (later stages)

These insights help guide personalized nutrition, exercise, and treatment strategies to improve metabolic function.

What to Do If You Have Insulin Resistance

Testing is just the first step. Effective management may include:

1. Nutrition: Focus on whole, nutrient-dense foods — vegetables, lean proteins, healthy fats, and fibre. Reduce refined carbs and sugar.

2. Exercise: Incorporate both strength training and aerobic exercise, which enhance insulin sensitivity.

3. Sleep and Stress: Poor sleep and chronic stress elevate cortisol, worsening insulin resistance.

4. Functional Support: Depending on your results and nutritional status, your naturopathic doctor may recommend targeted nutrients (e.g. magnesium, berberine, chromium, alpha-lipoic acid, vitamin D) and periodic lab monitoring.

Summary: Key Takeaways

• Insulin resistance often develops years before blood sugar abnormalities.

• Testing fasting insulin, glucose, and HOMA-IR gives early insight into metabolic health.

• Functional testing and CGMs reveal subtle glucose patterns missed by standard labs.

• Early detection empowers proactive, natural intervention and long-term prevention.

Disclaimer: This information is for educational purposes only and is not intended to provide or replace medical advice, diagnosis, or treatment. Always consult your qualified healthcare provider for individualized recommendations.