What is HOMA-IR? A plain guide to the insulin resistance score

What it estimates

Insulin resistance means muscle, fat and liver cells respond less well to insulin, so the pancreas makes more to keep glucose normal. NIDDK explains that over time the pancreas may not keep up, and glucose starts to rise. HOMA-IR, short for homeostatic model assessment of insulin resistance, uses a fasting snapshot of glucose and insulin to estimate where you are in that process.

StatPearls describes HOMA-IR as a widely used measure of insulin resistance in clinical research and notes that measures of insulin resistance have not been integrated into clinical guidelines. That is an important context for how much weight to place on it.

How it's calculated

HOMA-IR is not a separate blood test. It is calculated from two results: fasting glucose and fasting insulin, both drawn after an 8 to 12 hour fast. The formula is simple.

• If glucose is in mg/dL: glucose × insulin (µIU/mL) ÷ 405
• If glucose is in mmol/L: glucose × insulin (µIU/mL) ÷ 22.5

Why thresholds are slippery

You will see many different HOMA-IR cutoffs quoted online. Published thresholds vary by population, age, ethnicity and body size. Insulin assays are also not standardized between laboratories, so the same blood sample can produce noticeably different insulin values, and therefore different HOMA-IR scores, at different labs.

For those reasons, HOMA-IR is more trustworthy as a personal trend measured at the same lab than as a single number compared with a universal cutoff.

It isn't a diagnosis

Prediabetes and diabetes are diagnosed with glucose-based tests: A1C, fasting glucose or an oral glucose tolerance test. NIDDK notes that clinicians generally do not test for insulin resistance itself in routine care. A raised HOMA-IR is a signal that the body is compensating, which can be useful for motivation and for tracking, but it is not a disease label or, by itself, a reason for medicine.

Where it falls down

The model assumes the pancreas is still able to compensate. When that breaks down, HOMA-IR becomes unreliable.

• Later-stage type 2 diabetes, where insulin output is falling, can produce a falsely reassuring score
• Type 1 diabetes and people taking insulin
• Pregnancy
• Significant liver or kidney disease
• Samples that were not truly fasting
• High-dose biotin, which MedlinePlus advises stopping at least a day before an insulin test

What tends to improve it

The levers that improve insulin sensitivity are well established.

• Regular resistance training to build muscle that takes up glucose
• Short walks after meals
• Seven or more hours of sleep
• Losing visceral fat; even modest weight loss helps
• Cutting back on alcohol and sugary drinks

Reading it alongside other clues

HOMA-IR is most informative alongside other signs of insulin resistance. StatPearls lists features of metabolic syndrome, including a large waist, triglycerides of 150 mg/dL or more, low HDL, raised blood pressure and fasting glucose of 100 mg/dL or more. A triglyceride-to-HDL ratio above about 3 also correlates with insulin resistance in some populations.

If HOMA-IR looks fine but your waist is growing and triglycerides are rising, trust the overall pattern.

A worked example

Suppose your fasting glucose is 95 mg/dL and your fasting insulin is 12 µIU/mL. Multiply 95 by 12 to get 1,140, then divide by 405, giving a HOMA-IR of about 2.8. If six months later, after regular strength training and better sleep, your insulin is 8 µIU/mL with the same glucose, HOMA-IR falls to about 1.9. The direction of change, at the same lab, is the useful information, more than whether either number crosses a particular published cutoff.

Who might consider it

HOMA-IR can be helpful if you have a family history of type 2 diabetes, a growing waist, high triglycerides or a history of gestational diabetes or PCOS, and want an early read on insulin resistance before glucose changes. It is less useful if you already have diabetes or take insulin.

How often to recheck

Retesting is most useful after several months of real change in training, sleep, weight or medicine, rather than every few weeks. A HealifyMD clinician can include fasting insulin and glucose in your workup and explain the result in context. The Comprehensive Lab Panel is $199, confirmed at your eligibility review.