What Is Insulin Resistance And How Is It Detected?

Insulin resistance is the reduced response of the body to the hormone insulin. Insulin helps carry glucose in the blood into the cells. When cells do not respond adequately to insulin, the pancreas tries to produce more insulin to balance blood sugar. When this condition continues for a long time, metabolic balance may be disrupted.

Insulin resistance may not always cause obvious complaints on its own. Therefore, even if a person feels well, evaluation may be needed with measurements such as fasting blood glucose, fasting insulin, HbA1c and, when necessary, HOMA-IR. Insulin resistance may be an important risk indicator for prediabetes, type 2 diabetes, obesity, fatty liver and metabolic syndrome.

The World Health Organization states that type 2 diabetes accounts for the vast majority of all diabetes cases and that it is strongly associated with modifiable risk factors such as excess weight, physical inactivity and unhealthy diet. Therefore, early recognition of insulin resistance is important not only for blood sugar monitoring but also for reducing the risk of long-term metabolic disease.

What Does Insulin Do In The Body?

Insulin is one of the main hormones secreted by the pancreas and enables blood sugar to be used by the cells. After meals, glucose in the blood rises. Insulin helps transport this glucose into muscle, fat and liver cells. In this way, blood sugar is kept within a certain range.

When insulin resistance develops, cells no longer respond to this hormone as well as before. The pancreas may secrete more insulin to achieve the same effect. At the beginning, blood sugar may appear normal; however, this balance may be maintained with high insulin levels. Therefore, not only fasting blood glucose but also fasting insulin may be a valuable indicator in some patients.

The main functions of insulin are:

• Regulating Blood Sugar: It helps glucose enter the cells and supports blood sugar balance.
• Managing Energy Use: It plays an important role in carbohydrate, fat and protein metabolism.
• Affecting Liver Glucose Production: It helps regulate how much glucose the liver releases into the blood.
• Affecting Fat Storage: It plays a role in metabolic processes related to the storage of excess energy in fat tissue.

What Causes Insulin Resistance?

Insulin resistance usually does not develop due to a single cause. Genetic predisposition, abdominal fat accumulation, sedentary lifestyle, irregular nutrition, sleep problems, stress, certain hormonal diseases and weight gain may all play a role together. Fat accumulation around the waist is especially closely associated with insulin resistance.

The World Health Organization defines overweight and obesity as abnormal or excessive fat accumulation that presents a risk to health. Obesity is an important risk factor for many chronic diseases, including type 2 diabetes, cardiovascular diseases and some types of cancer.

The main factors that may contribute to insulin resistance include:

• Abdominal Fat Accumulation: Visceral fat tissue is metabolically active and may negatively affect insulin response.
• Sedentary Lifestyle: Since muscle tissue plays an important role in glucose use, low physical activity may reduce insulin sensitivity.
• Refined Carbohydrate-Heavy Diet: Sugary drinks, white flour-based foods and frequent snacking may challenge the blood sugar-insulin balance.
• Sleep Irregularity: Insufficient and poor-quality sleep may negatively affect appetite, weight and glucose metabolism.
• Genetic Predisposition: People with a family history of type 2 diabetes or metabolic disease may have a higher risk.
• Polycystic Ovary Syndrome: This is one of the hormonal conditions frequently associated with insulin resistance in women.

Which Symptoms May Suggest Insulin Resistance?

Insulin resistance does not always cause symptoms. In some people, blood sugar may remain within the normal range for a long time, while insulin levels may remain high. Therefore, it is not possible to determine whether insulin resistance exists based only on complaints. Still, some findings may increase the need for evaluation.

Symptoms such as sleepiness after meals, frequent hunger, craving for sweets, difficulty losing weight, fat accumulation around the waist and low energy may be seen together with insulin resistance. These symptoms do not establish a diagnosis on their own; however, they may be guiding when interpreted together with blood tests.

Symptoms that may be associated with insulin resistance include:

• Sleepiness After Meals: Significant fatigue may occur especially after carbohydrate-heavy meals.
• Frequent Hunger: Due to blood sugar fluctuations, the person may feel hungry again within a short time.
• Craving For Sweets: Increased desire for sweets or carbohydrates, especially in the evening, may be noticeable.
• Difficulty Losing Weight: Weight loss may progress slowly despite calorie restriction.
• Fat Accumulation Around The Waist: Abdominal fat accumulation is an important indicator of metabolic risk.
• Darkening Of The Skin: Velvety darkening on the neck, armpits or groin may be associated with insulin resistance in some people.

How Is Insulin Resistance Detected?

The most commonly used approach in evaluating insulin resistance is the combined interpretation of fasting blood glucose, fasting insulin and HOMA-IR calculation. In addition, tests such as HbA1c, postprandial blood glucose, oral glucose tolerance test and lipid profile help understand the person’s overall metabolic status.

The American Diabetes Association 2026 standards state that measurements such as fasting plasma glucose, HbA1c and oral glucose tolerance test are used in the diagnosis of diabetes and prediabetes. Insulin resistance evaluation is usually performed together with these tests as well as the person’s weight, waist circumference, family history and clinical findings.

The main tests used in insulin resistance evaluation are:

• Fasting Blood Glucose: This shows the glucose level in the blood after at least 8 hours of fasting.
• Fasting Insulin: This shows how much insulin the pancreas secretes during fasting.
• HOMA-IR: This is an indicator calculated with fasting blood glucose and fasting insulin, providing an idea about insulin resistance.
• HbA1c: This shows the average blood sugar level over approximately the last 2-3 months.
• Postprandial Blood Glucose: This helps evaluate the blood sugar response after meals.
• Oral Glucose Tolerance Test: This measures the body’s response to a glucose load and may be used to evaluate prediabetes/diabetes risk.

What Is HOMA-IR?

HOMA-IR is a calculation method used to evaluate insulin resistance. It is calculated using fasting blood glucose and fasting insulin values together. This value provides an idea about how sensitive or resistant the body may be to insulin.

A HOMA-IR result alone does not mean a definitive diagnosis. Laboratory reference ranges, measurement method, the person’s age, weight, waist circumference, accompanying diseases and medications used should be evaluated together. Therefore, it is more accurate for the results to be interpreted by an endocrinology doctor.

Points considered in HOMA-IR evaluation include:

• Fasting State: A fasting blood sample is usually required for the test to be interpreted correctly.
• Glucose And Insulin Together: Insulin alone or glucose alone may not be sufficient.
• Reference Ranges: HOMA-IR threshold values may vary depending on the laboratory and population.
• Clinical Context: The result should be interpreted together with weight, waist circumference, family history and other blood values.

Why Are HbA1c And Fasting Blood Glucose Evaluated Together?

Fasting blood glucose shows the glucose level at the time of measurement, while HbA1c reflects a longer-term average. Therefore, the two tests complement each other. A person’s fasting blood glucose may be borderline, while the HbA1c value may show that blood sugar balance has started to deteriorate in recent months.

The World Health Organization emphasizes the importance of blood glucose measurement in the diagnosis and follow-up of diabetes. Symptoms of diabetes may include frequent urination, thirst, weight loss, blurred vision and fatigue; however, some people may have no obvious symptoms for a long time.

The reasons why these two tests are evaluated together include:

• Providing Short- And Long-Term Information: Fasting glucose shows an immediate value, while HbA1c shows the long-term blood sugar trend.
• Identifying Prediabetes Risk: Risky ranges may be noticed before blood sugar reaches the diabetes level.
• Guiding The Treatment Plan: Nutrition, exercise, weight management and medication needs can be evaluated more accurately.
• Providing Comparison During Follow-Up: Metabolic response can be observed by monitoring changes over time.

What Is The Difference Between Insulin Resistance And Prediabetes?

Insulin resistance is the reduced response of cells to insulin. Prediabetes is an intermediate condition in which blood sugar values are above normal but have not reached the diagnostic threshold for diabetes. These two conditions may occur together, but they are not the same thing.

NIDDK states that insulin resistance and prediabetes may occur before the development of type 2 diabetes and that the risk can be reduced with lifestyle changes, weight management and medication when necessary. Therefore, insulin resistance detected early offers an important opportunity in preventive healthcare.

The main differences are:

• Insulin Resistance: This is the reduced response of the body to insulin; blood sugar may be normal.
• Prediabetes: This is a condition in which blood sugar values are higher than normal but below the diabetes threshold.
• Coexistence: Insulin resistance may pave the way for prediabetes.
• Need For Follow-Up: Regular blood sugar and metabolic risk follow-up is important in both conditions.

Who Is More Likely To Have Insulin Resistance?

Insulin resistance may be seen more frequently in people with excess weight, obesity, sedentary lifestyle, family history of type 2 diabetes and abdominal fat accumulation. However, insulin resistance may also develop in people with normal weight. Therefore, looking only at body weight is not enough.

Factors such as waist circumference, blood pressure, triglycerides, HDL cholesterol, fasting blood glucose and family history should be evaluated together. Especially in people with weight gain at a young age, recurrent sweet cravings, fatty liver or polycystic ovary syndrome, evaluation for insulin resistance may be performed.

Groups in which risk may be higher include:

• Overweight Or Obese Individuals: As fat tissue increases, insulin sensitivity may decrease.
• People With Increased Waist Circumference: Abdominal fat accumulation is considered important for metabolic risk.
• Those With A Family History Of Diabetes: Genetic predisposition may increase the risk of insulin resistance.
• Women With Polycystic Ovary Syndrome: Insulin resistance may be more common due to hormonal and metabolic effects.
• People With A Sedentary Lifestyle: Reduced muscle activity may negatively affect glucose use.
• People With Fatty Liver: Insulin resistance and fatty liver are often found on the same metabolic background.

What Can Happen If Insulin Resistance Is Not Treated?

If insulin resistance is not recognized or managed for a long time, it may become associated with problems such as prediabetes, type 2 diabetes, fatty liver, metabolic syndrome, hypertension and abnormal blood lipids. This process varies from person to person, and it does not mean that everyone with insulin resistance will necessarily develop diabetes.

However, risk can be reduced in the early period through lifestyle changes, weight management, physical activity, nutrition planning and physician follow-up. The World Health Organization recommends maintaining a healthy body weight, being physically active, eating a healthy diet and avoiding tobacco use to reduce the risk of type 2 diabetes.

Conditions that may be associated with uncontrolled insulin resistance include:

• Prediabetes: Blood sugar values may rise above normal.
• Type 2 Diabetes: Over time, the pancreas’ capacity to produce insulin may become insufficient.
• Metabolic Syndrome: Increased waist circumference, blood pressure, triglycerides and blood sugar abnormalities may occur together.
• Fatty Liver: Insulin resistance may affect liver fat metabolism.
• Cardiovascular Risk: Blood sugar, blood pressure and cholesterol abnormalities may create risk together.

Which Blood Values Are Important In Insulin Resistance Follow-Up?

Insulin resistance follow-up should not be based only on the HOMA-IR result. Blood sugar, HbA1c, lipid profile, liver enzymes, kidney function and, if necessary, vitamin-mineral values should be evaluated together. Because insulin resistance is often part of a broader metabolic picture.

Regular follow-up becomes more important especially in people with obesity, type 2 diabetes risk, hypertension, fatty liver or family history. Follow-up frequency should be determined by the physician according to the person’s risk level.

The main blood values that may be evaluated during follow-up include:

• Fasting Blood Glucose: This is one of the basic indicators of glucose metabolism.
• Fasting Insulin: This may provide information about insulin production and possible hyperinsulinemia.
• HbA1c: This shows the average blood sugar level of recent months.
• Lipid Profile: LDL, HDL, total cholesterol and triglyceride values are important for cardiometabolic risk.
• ALT, AST And GGT: These may be evaluated in terms of fatty liver or liver metabolism.
• Creatinine And eGFR: These provide information about kidney function.
• CRP: This may be requested in some people to evaluate inflammation level.

When Should You See An Endocrinology Doctor For Insulin Resistance?

It is not correct for everyone suspected of insulin resistance to interpret tests or plan treatment on their own. Fasting insulin, HOMA-IR, HbA1c and glucose values should be evaluated together with age, weight, medication use, pregnancy status, hormonal diseases and family history.

Endocrinology evaluation is especially important if there is rapid weight gain, difficulty losing weight, menstrual irregularity, fatty liver, prediabetes, history of type 2 diabetes, high triglycerides or family history of diabetes. If necessary, a personalized nutrition, exercise, medication or advanced testing plan may be created.

Situations that may require consulting an endocrinology doctor include:

• Elevated HbA1c Or Fasting Blood Glucose: Evaluation is needed for prediabetes or diabetes.
• High HOMA-IR: It should be interpreted together with the clinical picture.
• Increased Waist Circumference And Difficulty Losing Weight: Metabolic risk may need to be examined in detail.
• Polycystic Ovary Syndrome Findings: Evaluation may be performed if menstrual irregularity, excess hair growth and weight gain are present.
• Family History Of Type 2 Diabetes: Risk should be followed more closely.
• Fatty Liver: It should be examined in terms of metabolic processes associated with insulin resistance.

Happ Health And Online Endocrinology Doctor Support

Insulin resistance is not only a condition related to blood sugar. It is a metabolic process that should be evaluated together with weight control, appetite balance, waist circumference fat accumulation, liver health, cholesterol levels and type 2 diabetes risk. Therefore, interpreting blood tests individually and creating the right follow-up plan is important.

Happ Health is a digital health platform that facilitates access to specialist physician support in endocrinology through its online health application. For evaluation related to insulin resistance, prediabetes, obesity, GLP-1 treatment or type 2 diabetes risk, you can plan an online endocrinology doctor consultation and receive professional support in interpreting your blood values according to your health status.

References

• World Health Organization, Diabetes Fact Sheet
  https://www.who.int/news-room/fact-sheets/detail/diabetes
• World Health Organization, Diabetes Health Topic Page
  https://www.who.int/health-topics/diabetes
• World Health Organization, Obesity And Overweight Fact Sheet
  https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
• World Health Organization, Obesity Health Topic Page
  https://www.who.int/health-topics/obesity/obesity
• National Institute Of Diabetes And Digestive And Kidney Diseases, Insulin Resistance And Prediabetes
  https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance
• American Diabetes Association, Standards Of Care In Diabetes 2026
  https://professional.diabetes.org/standards-of-care
• American Diabetes Association, Diagnosis And Classification Of Diabetes: Standards Of Care In Diabetes 2026
  https://diabetesjournals.org/care/article/49/Supplement_1/S27/163926/2-Diagnosis-and-Classification-of-Diabetes
• American Diabetes Association, Obesity And Weight Management For The Prevention And Treatment Of Diabetes 2026
  https://diabetesjournals.org/care/article/49/Supplement_1/S166/163915/8-Obesity-and-Weight-Management-for-the-Prevention