Insulin Resistance: What It Is, Symptoms, Tests, Causes, and How to Reverse It

Insulin resistance means the body's cells don't respond normally to insulin, the hormone that helps move glucose from the blood into cells for energy. To compensate, the pancreas produces more insulin — and for a while, this can keep blood sugar in the normal range, which is part of why insulin resistance can exist for years before it's noticed.

Why It Develops

Insulin resistance is linked to excess body weight (particularly around the abdomen), physical inactivity, genetics, and age. Over time, if the pancreas can no longer keep up with the increased demand for insulin, blood sugar starts to rise — leading first to prediabetes and, without changes, potentially to type 2 diabetes.

How It's Recognized

Insulin resistance itself doesn't have a single specific blood test — it's usually inferred from blood sugar and HbA1c results, along with risk factors like weight, waist circumference, and family history. Some people also develop a skin change called acanthosis nigricans (dark, velvety patches, often on the neck or underarms) that can be a visible clue.

Who Is at Higher Risk

The NIDDK lists these risk factors for insulin resistance and prediabetes:

• Excess weight or a large waist
• Age 35 or older
• A family history of diabetes
• Physical inactivity
• Smoking or exposure to secondhand smoke
• Gestational diabetes in the past, or giving birth to a large baby
• Polycystic ovary syndrome (PCOS), sleep apnea, Cushing's syndrome
• Some medicines, including glucocorticoids and certain antipsychotic and HIV medicines

Symptoms: Why Most People Notice Nothing

People with insulin resistance and prediabetes usually have no symptoms, which is why it is often found by chance. Dark, velvety patches of skin on the neck or underarms (acanthosis nigricans) can be a visible clue and should prompt a check. Symptoms such as extreme thirst, frequent urination or unexplained weight loss suggest diabetes rather than insulin resistance alone — see high blood sugar symptoms. For a detailed list, read insulin resistance symptoms.

How Doctors Check

There is no single routine blood test for insulin resistance itself. Some doctors also look at waist size, blood pressure, cholesterol and triglycerides and liver tests, and researchers sometimes calculate scores from fasting insulin, but these are not standard everyday diagnostic tools.

Conditions Linked to Insulin Resistance

High blood pressure, abnormal cholesterol and triglycerides, fatty liver disease, metabolic syndrome, obesity, PCOS and type 2 diabetes are all associated with it. A doctor checking one of these often checks the others.

What Helps Improve Insulin Sensitivity

• Weight loss: losing 5% to 7% of your starting weight significantly reduces diabetes risk (NIDDK); if you are overweight, that is a realistic first target.
• Regular physical activity, including strength training, which helps muscles use glucose.
• A balanced eating pattern with more vegetables, legumes, whole grains and protein and less sugary drinks and refined starch — see best foods for diabetes and foods that lower blood sugar.
• Sleep and smoking: adequate sleep and stopping smoking both help.
• Medicine when appropriate: a doctor may consider metformin or other treatment for some people — this is an individual decision, see insulin resistance treatment.

Can Insulin Resistance Be Reversed?

Insulin sensitivity often improves substantially with the steps above, and progression to diabetes can often be delayed or prevented — read can prediabetes be reversed? and preventing type 2 diabetes. Ask an endocrinologist or your family doctor how to monitor progress.

Sources

• Insulin Resistance & Prediabetes — NIDDK