How Is Insulin Resistance Tested? A Complete Guide

Insulin resistance is difficult to diagnose because the body often maintains normal glucose levels for years by producing extra insulin. This means a standard glucose test may look completely normal even when insulin resistance is already present.

Still, several blood tests — when interpreted together — can offer important clues. This guide explains each test, what the numbers mean, and when testing may be helpful. For a broader overview, visit our complete insulin resistance guide.

In this article

• Why Insulin Resistance Is Hard to Test For
• 1. Fasting Glucose and Insulin
• 2. HOMA-IR
• 3. Oral Glucose Tolerance Test (OGTT)
• 4. HbA1c
• 5. Triglycerides & HDL
• 6. Clinical Clues Your Doctor Looks For
• When Should You Ask for Testing?

Why Insulin Resistance Is Hard to Test For

The pancreas can produce large amounts of insulin to compensate for resistance. As long as this extra insulin keeps blood glucose controlled, basic blood tests may appear normal. This is why insulin resistance often goes unnoticed for years before prediabetes or type 2 diabetes develops.

No single test can definitively diagnose insulin resistance — but patterns across multiple tests can provide a strong indication.

1. Fasting Glucose and Fasting Insulin

These are the most common initial tests. Glucose alone does not detect early insulin resistance, but fasting insulin provides additional insight.

Typical Patterns Suggestive of Insulin Resistance

Test	Typical Finding	What It Suggests
Fasting Glucose	Normal (≤5.5 mmol/L or ≤99 mg/dL)	Normal glucose does not exclude insulin resistance
Fasting Insulin	Raised (commonly >10–15 mIU/L)	The pancreas is overproducing insulin to compensate

High fasting insulin with normal glucose is one of the earliest measurable signs of reduced insulin sensitivity.

2. HOMA-IR (Homeostatic Model Assessment)

HOMA-IR is a calculated score using fasting glucose and insulin to estimate how hard the pancreas is working.

We will provide a full explainer soon at HOMA-IR: What Your Number Means.

While not routinely used in clinical practice, it is widely used in research and can indicate early metabolic dysfunction.

3. Oral Glucose Tolerance Test (OGTT)

An OGTT measures glucose (and sometimes insulin) after drinking a glucose solution. It reveals how the body handles a carbohydrate load.

• Normal glucose + high insulin → early insulin resistance
• Glucose between 7.8–11.0 mmol/L (140–199 mg/dL) → impaired glucose tolerance
• Glucose ≥11.1 mmol/L (≥200 mg/dL) → type 2 diabetes

OGTT is one of the most sensitive ways to detect early metabolic change but takes more time and is less commonly offered.

4. HbA1c

HbA1c reflects your average glucose over 3 months. It does not diagnose insulin resistance directly, but rising HbA1c may indicate that resistance has progressed.

5. Triglycerides and HDL

Insulin resistance often appears as a characteristic lipid pattern:

• Raised triglycerides (>1.7 mmol/L or >150 mg/dL)
• Low HDL cholesterol (<1.0 mmol/L in men, <1.3 mmol/L in women)

This combination (along with abdominal obesity or high blood pressure) forms part of metabolic syndrome.

6. Clinical Clues Doctors Look For

Beyond lab tests, doctors look for physical signs highly associated with insulin resistance, including:

• Acanthosis nigricans
• Multiple skin tags
• Central weight gain
• PCOS features in women
• Fatty liver on blood tests or ultrasound

Trusted External Sources

• NIDDK – Diabetes Tests
• CDC – Getting Tested for Diabetes

When Should You Ask for Insulin Resistance Testing?

You may wish to discuss testing with your doctor if you:

• have a family history of type 2 diabetes
• have symptoms such as fatigue, weight gain around the middle, or skin changes (see insulin resistance symptoms)
• have been diagnosed with PCOS
• have rising triglycerides or blood pressure
• had gestational diabetes

Testing does not need to be perfect to be useful. Even borderline abnormalities can motivate early, effective action. To understand practical steps, see How to Improve Insulin Sensitivity.