Insulin resistance: symptoms, how to test for it (fasting insulin, HOMA-IR) and what helps

Insulin resistance is a condition in which the body's cells, mainly in muscle, liver and fat, respond poorly to insulin, the hormone that moves sugar from the blood into cells. To compensate, the pancreas makes more insulin, and that extra insulin keeps blood sugar normal, often for years. ¹² That is why insulin resistance is easy to miss: a normal fasting glucose and A1C (a 3-month average of blood sugar) can sit alongside it, and NIDDK notes that clinicians may not test for it directly. ¹ When the pancreas can no longer keep up, blood sugar climbs into prediabetes and then type 2 diabetes. ² What to do next: if you have a fasting insulin, glucose, triglyceride or HDL result, bring the numbers to your clinician and ask how they read together, and whether an A1C or a 2-hour glucose test makes sense.

Acanthosis nigricans is the most specific visible sign. MedlinePlus describes it as dark, velvety skin with visible markings in the armpits, groin and neck folds, often linked to "hormone imbalances that occur in diabetes and obesity, often called insulin resistance," and it often fades once the cause is found and managed. ⁸ The ADA lists acanthosis nigricans among the conditions associated with insulin resistance that count as a reason to screen for diabetes. ³

What is insulin resistance?

After a meal, insulin from the pancreas tells muscle, liver and fat cells to take up glucose (blood sugar). In insulin resistance those cells respond less, so more insulin is needed for the same effect. The resulting high insulin, called hyperinsulinemia, can itself make the resistance worse, which sets up a cycle. ² StatPearls describes the consequences as high blood sugar, high blood pressure, abnormal blood fats, high uric acid, inflammation and a tendency to clot, and the conditions it leads to as metabolic syndrome, fatty liver and type 2 diabetes. ² PCOS also sits on the same spectrum. ²

Who gets insulin resistance and why

StatPearls calls insulin resistance mostly an acquired condition related to excess body fat, with some genetic causes. ² NIDDK says researchers do not fully understand the cause and lists the risk factors below. ¹ It is common: in 2021 about 97.6 million US adults had prediabetes, the later stage that insulin resistance leads to, and that number has barely moved in 15 years. ¹

• Overweight, obesity or a large waist ¹
• Age 35 or older, and a family history of diabetes ¹
• Physical inactivity and smoking ¹
• Certain racial and ethnic backgrounds, including African American, Hispanic or Latino, American Indian and Asian American people ¹³
• A history of gestational diabetes ¹
• PCOS, Cushing's syndrome, acromegaly and sleep apnea ¹
• Medicines such as glucocorticoids (steroids) ¹

What test shows insulin resistance?

The gold standard is the hyperinsulinemic-euglycemic clamp, a research procedure that infuses insulin and glucose for hours to measure how fast the body clears sugar. It is not used in routine care. ² Clinicians rely instead on surrogates: HOMA-IR, a second version called HOMA2, QUICKI, the triglyceride level and the triglyceride-to-HDL ratio. ² In practice, the glucose tests then show whether insulin resistance has progressed to prediabetes or diabetes. ³

Fasting matters for most of these. Labcorp asks for a fasting sample for insulin, and the ADA defines fasting as no calories for at least 8 hours. ³⁷ Insulin tests are not standardized between labs, which is why McLaughlin and colleagues at Stanford suggested the triglyceride level or the triglyceride-to-HDL ratio as the most practical screen: "In the absence of a standardized insulin assay," they wrote, those cut-points are the simplest way to find insulin-resistant overweight adults. ⁴ The lipid panel guide explains how triglycerides and HDL are reported.

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Educational, not a diagnosis. TG/HDL thresholds are population-dependent and a surrogate for insulin resistance, not a diagnosis of it. Bands describe the values, not you.

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HOMA-IR: how it is calculated and what the cutoffs mean

HOMA-IR (homeostasis model assessment of insulin resistance) was published in 1985 by Matthews and colleagues. It uses the fact that fasting glucose and fasting insulin settle at a balance point set by how resistant the body is and how well the pancreas responds. ⁵ The common shortcut is fasting insulin in µIU/mL times fasting glucose in mg/dL, divided by 405 (or glucose in mmol/L divided by 22.5). The HOMA-IR calculator does the arithmetic. In the original study the score tracked the clamp closely (correlation 0.88), but its precision was low, with a coefficient of variation of 31%, so one result can mislead. ⁵

The cutoff problem is real. In 2,459 Spanish adults, a HOMA-IR line set at the 90th percentile was 3.46, while a line chosen to pick out people with metabolic syndrome was 2.05, and 1.85 in men without diabetes; in women the best cutoff changed with age. ⁶ The authors describe "great variability in the threshold" across studies. ⁶ Population, sex, age and the insulin assay all move the number, so labs and studies elsewhere use other lines.

HOMA-IR 1.5, 2, 2.5, 3 or 8.5: what the number means

These readings use the EPIRCE cutoffs above and assume fasting insulin in µIU/mL and glucose in mg/dL. ⁶ Another lab or study may draw the line elsewhere, and the original authors put the estimate's imprecision at about 31%. ⁵

• HOMA-IR of 0.8 to 1.5: below every common study cutoff; insulin sensitivity looks good. A very low value with high glucose is a different picture, low insulin output, worth raising with a clinician. ⁶
• HOMA-IR of 2 to 2.5: borderline. Above the 1.85 and 2.05 cutoffs, below the 3.46 one; the lipid panel, waist and A1C decide how much weight it carries. ⁶
• HOMA-IR of 3 to 3.5: insulin resistant by most study cutoffs, and close to the 90th-percentile line. ⁶
• HOMA-IR of 5: well above every common cutoff; fasting insulin is usually clearly raised, and glucose status deserves a check with A1C or an oral glucose tolerance test. ³⁶
• HOMA-IR of 8.5: marked insulin resistance; fasting glucose at that level is often already in the prediabetes or diabetes range, so a diabetes workup usually follows. ³

How the insulin resistance markers read together

Conditions linked to or mistaken for insulin resistance

Insulin resistance is a mechanism more than a stand-alone diagnosis, so the related conditions are its stages and companions. ² Prediabetes is defined by glucose, not insulin; metabolic syndrome by waist, triglycerides, HDL, blood pressure and glucose; fatty liver by liver imaging and enzymes; and PCOS by cycles, androgens and ovarian findings. ²³⁹ A few conditions cause insulin resistance directly: Cushing's syndrome, acromegaly and steroid medicines, which a clinician considers when the picture is unusual, such as insulin resistance without excess weight. ¹ High blood sugar with weight loss and low insulin points to the opposite problem, too little insulin, as in type 1 diabetes. ³

What helps insulin resistance: the evidence, graded

Lifestyle change has the strongest evidence, and the gains start quickly. In the Diabetes Prevention Program, 3,234 adults with raised glucose were assigned to a lifestyle program (goals of at least 7% weight loss and 150 minutes of activity a week), metformin, or placebo; over about 2.8 years, lifestyle cut new diabetes by 58% and metformin by 31%. ¹⁰ Prescription options are listed below as facts; whether any fits is a decision for your clinician with you.

Monitoring and retesting

Because HOMA-IR and fasting insulin bounce between draws, a trend across two or three results tells you more than one. See why trends beat single readings and the blood sugar guide for how fasting glucose, A1C and the OGTT fit together.

When to see a doctor

Outside those red flags, the ADA recommends diabetes screening from age 35 for everyone, and earlier for adults with overweight or obesity plus a risk factor such as a family history of diabetes, high blood pressure, PCOS, low HDL or high triglycerides, or acanthosis nigricans. ³ Any of those is a reason to ask your clinician about glucose testing.

Questions to ask your clinician

• Do my triglycerides, HDL and waist suggest insulin resistance, even with a normal glucose?
• Would a fasting insulin or HOMA-IR add anything for me, and which cutoff does your lab use?
• Should I have an A1C or a 2-hour oral glucose tolerance test?
• Do I have signs of fatty liver, and should my ALT be followed?
• Could any of my medicines, such as steroids, be adding to insulin resistance?
• How often should these tests be repeated, and what change would mean progress?

Related reading: prediabetes, metabolic syndrome, the HOMA-IR and fasting insulin marker pages, and how reference ranges work. This page is general education, not medical advice or a diagnosis. The clinician who knows your history reads your results and makes decisions with you.