What Is Insulin Resistance and How Do You Know if You Have It?

If you’ve spent time online recently, you’ve likely heard of insulin resistance. People using injectable drugs like Ozempic talk about it. Fitness enthusiasts suggest exercise routines to reverse it. Influencers market supplements that supposedly counter it. But what exactly is insulin resistance and how do you know if you have it?

A Crucial Hormone

Insulin is a hormone secreted by the pancreas that is crucial for converting food into energy, or storing that energy for later.

When your blood glucose levels rise after a meal, the pancreas responds by producing insulin. The insulin, in turn, helps cells use the sugar and brings the amount of glucose in your bloodstream back to a normal range.

When you are insulin resistant, your body does not respond to insulin after meals as effectively as it should. This means your cells don’t take in enough glucose. The pancreas then produces more insulin to help the process along. Eventually, the pancreas becomes unable to keep up.

“After a number of years, your blood sugar starts to stay high after you eat and that ultimately leads to what we call pre-diabetes,” said Dr. Ruchi Mathur, an endocrinologist at Cedars-Sinai in Los Angeles.

A fasting blood glucose level between 100 to 125 mg/dL is considered pre-diabetes. If glucose levels remain untreated and become higher than 125 mg/dL, you would be diagnosed with Type 2 diabetes.

Who Should Be Concerned

According to the Centers for Disease Control and Prevention, 37.3 million adults have diabetes and 96 million — or more than one-third of Americans — have pre-diabetes. Because insulin resistance is a precursor to both, researchers estimate the number of people with insulin resistance is much higher.

“Most people don’t even know that they have it,” said Dr. Mary Vouyiouklis Kellis, an endocrinologist at Cleveland Clinic.

People with certain genetic conditions, such as myotonic dystrophy or lipodystrophy, often have insulin resistance. But more frequently, people develop insulin resistance as the result of a mix of social and biological factors, Dr. Kellis said. For example, if you have a family history of Type 2 diabetes, you may be more likely to have insulin resistance. If you’ve been diagnosed with high fat in your blood, such as high triglycerides, high LDL cholesterol, or low HDL cholesterol, you may also be at higher risk. Black, Hispanic, American Indian, Alaska Native and Asian people are known to have a higher risk.

Data suggests that insulin resistance also increases with age, as pancreatic function declines. It is also more likely to occur in people who are less physically active or have a poor diet.

Certain medications temporarily increase the risk of insulin resistance, including a class of steroids called glucocorticoids, some antipsychotics and some H.I.V. medicines, Dr. Kellis said. Some metabolic or hormonal diseases are associated with insulin resistance as well, including high blood pressure, heart disease, nonalcoholic fatty liver disease and polycystic ovary syndrome, or PCOS.

Early Signs to Look For

Doctors rely on many of the same cues and blood tests used for pre-diabetes and diabetes — like those that check your glucose levels or hemoglobin A1C — to determine if you have insulin resistance. “It’s a bit of art and science,” Dr. Mathur said.

The United States Preventive Services Task Force recommends that all adults 35 to 70 years old be tested for pre-diabetes if they are overweight or obese. The American Diabetes Association also suggests screening adults who have other risk factors for diabetes, such as a close relative with Type 2 diabetes, a diagnosis of PCOS, a history of gestational diabetes or clinical conditions associated with diabetes.

According to the A.D.A., all adults should start getting tested at age 45, even if they don’t have any risk factors. And if your results are normal but you notice symptoms or develop any risk factors for diabetes, you should ask to get retested at least every three years.

Often, there are no obvious signs until months or years after your body has been struggling to manage insulin and blood sugar levels. When they do appear, some of the earliest indicators tend to be related to how your body reacts after meals.

You feel hungry or tired all the time.

Because your body isn’t absorbing glucose efficiently, you may not get much of an energy boost from your food. As a result, you may feel excessively fatigued and your brain may keep signaling that you need to eat more sweet or carb-rich meals.

You’ve gained weight.

When your body starts to run out of places to store excess glucose in the liver and muscles, it starts converting the extra sugar into fat. This can compound the problem: More body fat can make insulin resistance even worse.

Research shows that visceral fat, in particular, which surrounds the organs in your abdomen, releases fatty acids, hormones and pro-inflammatory molecules into your blood. Long-term inflammation and an increase in circulating fat are associated with insulin resistance.

While waist size can’t be used to diagnose health issues, doctors do use it to screen for possible risks. Men with a waist circumference of more than 40 inches and nonpregnant women whose waist circumference is more than 35 inches are considered to have a higher risk of insulin resistance.

You can still have high levels of harmful fat in your cells even if your waist is smaller, said Dr. Gerald I. Shulman, a professor of medicine at Yale and co-director of the university’s Diabetes Research Center.

You notice darkened skin patches or skin tags.

Some people with more advanced insulin resistance also develop skin tags or a condition called acanthosis nigricans. This can look like dark patches in body folds like on the back or side of your neck, in your armpits or in your groin, Dr. Shulman said, adding that doctors often see these skin changes in people with PCOS who have insulin resistance.

Your period isn’t regular.

“Women’s cycles are a close marker of their health,” Dr. Mathur said. If you notice that your menstrual cycle is becoming irregular, or have other signs that indicate PCOS, such as increased acne or facial hair, a doctor may evaluate you for hormonal imbalances as well as insulin resistance, she said.

You drink more water or urinate more.

If insulin resistance progresses, elevated blood sugar levels may force your kidneys to start working harder and you may feel the urge to drink more and urinate more.

If you think something’s off, and you suspect it could be linked to insulin resistance, tell your doctor, Dr. Mathur said. “You know your body better than anybody else.”