What Is Insulin Resistance? Signs, Symptoms, Causes, and Treatment
Most people have heard of insulin, but many aren't sure what it actually does.
Insulin resistance is incredibly common and often develops years before someone is diagnosed. In fact, many people with insulin resistance have completely normal blood sugar levels.
It can be a common explanation for symptoms like fatigue, an afternoon energy crash, brain fog, increased hunger, or difficulty losing weight.
The good news is that it can often be improved with lifestyle changes and, when appropriate, medications or supplements.
What Is Insulin?
Insulin is a hormone made by your pancreas.
Its job is to move sugar (glucose) from your bloodstream into your body's cells, where it can be used for energy.
After you eat, your blood sugar rises and your pancreas releases insulin. Insulin acts like a key, unlocking your cells so glucose can enter.
What Is Insulin Resistance?
With insulin resistance (IR), your body's cells stop responding to insulin as well as they should.
Think of it like knocking on a door.
At first, insulin knocks and the door opens easily.
Over time, the cells become less responsive, so your body has to knock louder by producing more insulin to achieve the same effect.
For many years, your pancreas can often keep up by making extra insulin. During this stage, your blood sugar may still appear normal on routine lab work, even though insulin levels are already elevated.
Eventually, the pancreas may no longer be able to keep up, allowing blood sugar to rise and increasing the risk of prediabetes and type 2 diabetes.
Who Is at Risk?
Anyone can develop insulin resistance, but certain factors increase the risk:
Carrying excess weight, particularly around the abdomen
Physical inactivity
Family history of type 2 diabetes
Polycystic ovary syndrome (PCOS), now referred to as Polyendocrine Metabolic Ovarian Syndrome (PMOS)
Poor sleep or shift work
Chronic stress
Certain medications
Increasing age
Not everyone with insulin resistance is overweight. Some people develop insulin resistance despite having a normal body weight.
Common Signs and Symptoms
Many people have no symptoms at all.
Others may notice:
Fatigue, especially after meals
Increased hunger or frequent cravings
Difficulty losing weight
Weight gain around the abdomen
Brain fog
Energy crashes during the day
Elevated triglycerides or low HDL cholesterol
High blood pressure
In women, insulin resistance can also contribute to irregular periods, acne, and excess facial or body hair, particularly in those with PCOS/PMOS.
How Is It Diagnosed?
Insulin resistance cannot always be detected with a routine fasting glucose test.
A more comprehensive panel may include:
Fasting glucose + Fasting insulin (to calculate HOMA-IR score)
Hemoglobin A1C (HbA1c)
Lipid panel
Liver enzymes
Blood pressure and waist circumference
These results are interpreted alongside your symptoms, medical history, and overall health.
Can Insulin Resistance Be Reversed?
For many people, insulin sensitivity can improve significantly with a holistic approach:
Regular physical activity, including resistance training
Eating enough protein and fibre
Choosing minimally processed foods more often
Prioritizing good sleep
Managing stress
Achieving a healthy body composition, if appropriate
Taking medications or supplements when indicated and recommended by your healthcare provider
Small, consistent changes often have a much greater impact than trying to make dramatic changes all at once.
Why Does It Matter?
Left untreated, insulin resistance increases the risk of developing:
Prediabetes and Type 2 diabetes
High cholesterol and abnormal triglycerides
High blood pressure
Heart disease and stroke
Metabolic dysfunction-associated steatotic liver disease (MASLD, formerly NAFLD)
PMOS or worsening PMOS symptoms (PMOS was formerly called PCOS)
Fertility problems and ovulatory dysfunction
Obstructive sleep apnea
The earlier insulin resistance is identified, the more opportunity there is to improve metabolic health and reduce the risk of future disease.
Overview
Insulin resistance is common, but it often goes unnoticed because blood sugar can remain normal for years.
Understanding your risk factors and identifying insulin resistance early allows you to take steps to improve your metabolic health before more serious problems develop.
If you're experiencing fatigue, difficulty losing weight, elevated cholesterol, PCOS/PMOS, or have a family history of diabetes, it may be worth discussing your metabolic health.
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References
Petersen MC, Shulman GI. Mechanisms of insulin action and insulin resistance. Physiological Reviews. 2018.
American Diabetes Association. Standards of Care in Diabetes. 2025.
DeFronzo RA, Ferrannini E, Groop L, et al. Type 2 diabetes mellitus. Nature Reviews Disease Primers. 2015.
Taylor R. Type 2 diabetes: etiology and reversibility. Diabetes Care. 2013.
Samuel VT, Shulman GI. The pathogenesis of insulin resistance. Cell. 2016.
