What Is HOMA-IR? The Insulin Resistance Number, Explained
Labs · Insulin · Updated 2026-07-31
HOMA-IR = fasting insulin (uIU/mL) x fasting glucose (mg/dL) / 405. It is a two-lab estimate of insulin resistance, and most laboratories read values below about 1.9 as insulin sensitive, 1.9 to 2.5 as early or borderline, and 2.5 and above as commonly flagging insulin resistance, with many labs drawing their own line closer to 2.9. There is no single official cut point, so your lab's printed range wins over any number on the internet.
It matters in PCOS because insulin resistance is reported in a large share of people with the condition, including many at a normal body weight. The 2023 international evidence-based guideline for the assessment and management of polycystic ovary syndrome treats insulin resistance as a common feature of PCOS while stating plainly that insulin measurement is not part of diagnosing it, because insulin assays are not standardised between laboratories. HOMA-IR is therefore a tracking number and a conversation starter with your doctor, not a diagnosis.
The formula, worked in both unit systems
Conventional US units use a divisor of 405 with glucose in mg/dL. Fasting insulin 11 uIU/mL and fasting glucose 92 mg/dL gives 11 x 92 / 405 = 2.50. SI units use a divisor of 22.5 with glucose in mmol/L: 11 mU/L x 5.1 mmol/L / 22.5 = 2.49. The two agree because 1 mmol/L of glucose is about 18 mg/dL. If a calculator hands you a number that looks roughly eighteen times too large or too small, you have mixed the two systems.
Now run the same person a year later at fasting insulin 8 uIU/mL and fasting glucose 88 mg/dL: 8 x 88 / 405 = 1.74. Nothing about their HbA1c or their weight had to change for that improvement to be real and measurable. Two inexpensive labs, one clear direction.
| HOMA-IR | Common interpretation | What often happens next |
|---|---|---|
| Below 1.0 | Comfortably insulin sensitive | No extra metabolic follow-up beyond routine screening |
| 1.0 to 1.9 | Within the usual insulin-sensitive range | Recheck if symptoms, family history or cycle changes suggest risk |
| 1.9 to 2.5 | Early or borderline resistance at many labs | Food, movement and sleep discussion; repeat fasting labs in 3 to 12 months |
| 2.5 to 2.9 | The most widely cited single cut point for insulin resistance | Fuller metabolic workup: HbA1c, lipids, sometimes an oral glucose tolerance test |
| 2.9 and above | Significant insulin resistance for most laboratories | Discuss treatment options and a re-test interval with your clinician |
The other numbers on the same blood draw
| Marker | Typical reference | Why it is there |
|---|---|---|
| Fasting glucose | 70 to 99 mg/dL (3.9 to 5.5 mmol/L) | 100 to 125 mg/dL is the prediabetes band used by the American Diabetes Association |
| Fasting insulin | Roughly 2 to 20 uIU/mL depending on assay | No standardised optimal value exists; many clinicians simply prefer to see single digits |
| HbA1c | Below 5.7 percent | 5.7 to 6.4 percent is prediabetes, 6.5 percent and above is diabetes |
What HOMA-IR cannot tell you
- It is not diagnostic of PCOS. The 2023 international PCOS guideline diagnoses PCOS from the Rotterdam criteria, and explicitly excludes insulin measurement from that process.
- It assumes a genuine fasting state. Eight to twelve hours with water only. Coffee with milk, an illness, a night shift or a recent steroid course can move either input.
- It can look falsely reassuring in later-stage disease. Once beta cell function starts to fail, insulin output falls even while resistance stays high, and HOMA-IR drops for the wrong reason.
- One value is close to meaningless. Day-to-day biological variation in fasting insulin is substantial. Three values across two years are informative in a way that a single reading never is.
Why PCOS care teams watch this number
High circulating insulin does two specific things that matter in PCOS. It stimulates the ovarian theca cells to produce more androgens, and it suppresses production of sex hormone binding globulin (SHBG) by the liver, which raises the free, biologically active fraction of testosterone. That is the mechanical bridge between a metabolic lab result and the symptoms people actually live with: acne along the jaw, hirsutism, scalp hair thinning, and cycles that stretch out because ovulation becomes infrequent.
Because the loop runs in both directions, HOMA-IR is one of the few PCOS numbers that can respond within a few months to things within reach - the overall food pattern, resistance training and walking after meals, regular sleep, and medications a clinician may prescribe. Body weight usually moves last, which is precisely why judging progress by the scale discourages people whose metabolic picture is already improving.
Your fasting labs, tracked over time. PCOS Diet & Symptom Tracker by Panda Taps lets you log fasting insulin and glucose with their units and reference ranges, alongside your symptoms, meals and cycles. Instead of a single number remembered from a portal, you walk into your next appointment with a dated history your doctor can read at a glance. It is a tracking tool, not a diagnostic or treatment device. Download PCOS Diet & Symptom Tracker on the App Store.
Getting the labs, and what to ask
- Ask for fasting insulin by name: Fasting glucose sits on nearly every routine panel; fasting insulin usually does not. Without it HOMA-IR cannot be calculated at all, so request it explicitly rather than assuming it is included.
- Fast properly and consistently: Eight to twelve hours, water only, ideally a morning draw. Repeat future draws under the same conditions so you are comparing like with like.
- Write down units and the lab's ranges: Note whether insulin came back in uIU/mL or pmol/L and glucose in mg/dL or mmol/L. Reconstructing units from memory months later is where most errors creep in.
- Ask what result would change the plan: A genuinely useful question for the appointment: at what value would you add or change treatment, and when should we retest?
HOMA-IR is one line in a larger picture. Pair it with the wider PCOS blood test list and what insulin resistance looks like day to day. Educational content only; testing and treatment decisions belong with your clinician.
Frequently asked questions
What is a normal HOMA-IR?
Many laboratories treat values under about 1.9 as insulin sensitive, with 2.5 the most widely cited cut point for insulin resistance and some labs using 2.9. Cut points are not standardised, so interpret your value against your own lab's range with your doctor.
Can I have insulin resistance with normal glucose?
Yes, and that is exactly what HOMA-IR is designed to catch. Fasting insulin can run high for years while glucose and HbA1c stay in range, because the extra insulin is what is holding glucose normal.
How often should HOMA-IR be rechecked?
There is no fixed schedule. Many clinicians repeat fasting insulin and glucose every 3 to 12 months when following a change, and the 2023 international PCOS guideline suggests glycaemic screening every one to three years depending on individual risk. Follow your doctor's plan.
Is HOMA-IR reliable enough to act on?
It is an estimate rather than the gold-standard clamp test, and it is affected by fasting state and assay differences. It is inexpensive and repeatable, which makes it good for watching direction over time and poor for reading a single number in isolation.