Blood Tests for Insulin Resistance
The full panel of markers to ask your GP for — which are bulk-billed, which are private-pay, what each result means, and how to read the combined picture.
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Why Insulin Resistance Has No Single Test
Insulin resistance is a metabolic state, not a single abnormal number. It manifests across multiple organ systems simultaneously — the liver over-produces glucose and triglycerides, fat cells release excess fatty acids, and muscle cells fail to take up glucose efficiently. Each of these disturbances leaves a trace in your blood test.
The most direct test is fasting insulin (with HOMA-IR calculated from fasting glucose). But several Medicare-bulk-billed markers — triglycerides, HDL, ALT, GGT, and fasting glucose — together paint a nearly as informative picture at zero extra cost. This page covers the complete panel, what each marker means, and how to interpret the cluster.
The Insulin Resistance Panel — Every Marker Explained
Direct markers measure insulin or its immediate effects. Surrogate markers reflect downstream metabolic disturbances driven by insulin resistance. Both types are clinically useful.
Fasting insulin(mIU/L (or pmol/L))
The most direct blood measure of insulin resistance. Lab reference range (2-25 mIU/L) is too wide for clinical utility - use optimal targets. Private-pay ~$20-$40.
HOMA-IR (calculated)(Ratio (no units))
Calculated as (glucose mmol/L x insulin mIU/L) / 22.5. Combines both markers into a single insulin resistance estimate. Not reported by labs - you calculate it yourself.
Fasting glucose(mmol/L)
Bulk-billed on Medicare. Rises late in insulin resistance - a normal result does not rule out significant insulin resistance. Essential for HOMA-IR calculation.
HbA1c(% or mmol/mol)
Bulk-billed on Medicare. Reflects average glucose over the past 3 months. Like fasting glucose, rises late. Useful for monitoring once prediabetes or diabetes is established.
Triglycerides (fasting)(mmol/L)
Bulk-billed as part of the standard lipid panel. Insulin resistance drives VLDL overproduction, raising triglycerides. One of the most sensitive and practical surrogate markers.
HDL cholesterol(mmol/L)
Bulk-billed. Low HDL is tightly coupled with elevated triglycerides in insulin-resistant dyslipidaemia. HDL is metabolised faster when triglycerides are high, lowering its level.
TG:HDL ratio(Ratio (mmol/L units))
Calculated from Medicare-bulk-billed results. A TG:HDL ratio above 1.8 (in mmol/L) is a cheap, practical surrogate for insulin resistance and small dense LDL - correlates strongly with HOMA-IR.
ALT (alanine aminotransferase)(U/L)
Part of the liver function panel, bulk-billed. Elevated ALT in the setting of high triglycerides and insulin resistance strongly suggests metabolic-associated steatotic liver disease (MASLD/NAFLD).
GGT (gamma-glutamyl transferase)(U/L)
Sensitive to liver fat and alcohol. In non-drinkers, elevated GGT alongside ALT and insulin resistance markers strongly indicates fatty liver. Also rises with oxidative stress.
Uric acid(umol/L)
Private-pay (~$15-$25). Often elevated in insulin resistance and metabolic syndrome because insulin reduces renal uric acid excretion. Elevated uric acid is also an independent cardiovascular risk factor.
The TG:HDL Ratio — A Free Surrogate You Already Have
If you have ever had a standard lipid panel, you already have everything needed to calculate a powerful surrogate marker for insulin resistance. Divide your fasting triglycerides by your HDL cholesterol (both must be in mmol/L for the Australian cut-offs to apply).
TG:HDL Ratio = Triglycerides (mmol/L) ÷ HDL (mmol/L)
Example: Triglycerides 2.1 mmol/L, HDL 1.1 mmol/L → TG:HDL = 2.1 ÷ 1.1 = 1.91 — above 1.8, suggesting likely insulin resistance.
Below 1.0
Excellent insulin sensitivity and low small dense LDL concentration. Maintain with current habits.
1.0-1.8
Possible mild insulin resistance or early dyslipidaemia. Consider adding fasting insulin to your next test.
Above 1.8
Strong surrogate for insulin resistance and small dense LDL. Even without fasting insulin, this warrants lifestyle action.
Reading the Combined Picture — Cluster Patterns
The diagnostic value of these markers comes from reading them together. These are the most common and clinically significant cluster patterns.
Classic insulin resistance triad
High confidence for significant insulin resistance. Warrants HOMA-IR calculation, lifestyle intervention, and 12-week follow-up blood test.
Fatty liver metabolic pattern
Likely metabolic-associated steatotic liver disease (MASLD/NAFLD) driven by insulin resistance. Ultrasound abdomen and hepatology review may be warranted if ALT is consistently elevated.
Pre-prediabetic early warning
Insulin resistance is present but glucose homeostasis is still maintained by compensatory hyperinsulinaemia. The optimal time to intervene - before glucose markers rise.
Surrogate-only elevation (no fasting insulin tested)
Strong circumstantial evidence for insulin resistance without direct measurement. Consider adding fasting insulin to the next blood test for confirmation.
Red Flags — Results That Need Prompt GP Review
Fasting glucose above 5.6 mmol/L plus HOMA-IR above 2.9
You are at the prediabetes boundary with confirmed insulin resistance. This combination predicts progression to type 2 diabetes within 5-10 years without intervention. Warrants a formal prediabetes management plan with your GP.
ALT above 60 U/L with no alcohol use
Significant liver inflammation, likely from metabolic steatohepatitis (MASH). An abdominal ultrasound is appropriate, and a FibroScan (liver stiffness measurement) may be recommended to stage any liver damage.
Triglycerides above 5.0 mmol/L
Very high triglycerides raise the risk of acute pancreatitis. Requires urgent GP review and usually medical treatment (fibrates) in addition to lifestyle changes. Also makes LDL-C calculation unreliable - request a direct LDL or ApoB measurement.
Uric acid above 480 umol/L plus insulin resistance pattern
Gout and insulin resistance are closely linked through shared metabolic pathways. Very high uric acid combined with insulin resistance markers substantially raises cardiovascular risk and should be managed alongside the metabolic syndrome picture.
Rising ALT plus rising fasting insulin on serial testing
Progressive worsening of both markers suggests that liver fat is accumulating despite current measures. Escalation of treatment (dietitian referral, consideration of GLP-1 agonist or other medical intervention) is warranted.
What to Do Next — A Step-by-Step Plan
Book a fasting blood test with your GP
Ask for: fasting glucose, fasting insulin, full lipid panel (triglycerides + HDL), liver function tests (ALT + GGT), HbA1c, and uric acid. Everything except fasting insulin and uric acid is Medicare bulk-billed. Fast for 10-12 hours beforehand.
Calculate your HOMA-IR from the results
Use the formula: (fasting glucose mmol/L x fasting insulin mIU/L) / 22.5. Calculate your TG:HDL ratio by dividing your triglyceride result by your HDL result (both in mmol/L).
Look for the cluster pattern
A single elevated marker is less meaningful than a cluster. If 3-4 of the surrogate markers above are moving in the wrong direction simultaneously, insulin resistance is highly likely even without a fasting insulin result.
Discuss with your GP and set targets
Share the full picture with your GP. Agree on target values: fasting insulin below 7 mIU/L, HOMA-IR below 1.5, triglycerides below 1.0 mmol/L, TG:HDL below 1.0. These are more ambitious than standard lab reference ranges but are evidence-based metabolic targets.
Retest at 12-16 weeks after lifestyle changes
After implementing dietary changes, increased exercise, improved sleep, and weight loss (if applicable), retest the full panel. Fasting insulin typically responds faster than HbA1c, making it a more sensitive early indicator of improvement.
Track the trend with all markers visible together
Upload your blood test PDFs to SmarterBlood to plot fasting insulin, HOMA-IR, triglycerides, HDL, ALT, and glucose on the same timeline. Seeing the full picture in one place makes it much easier to understand which interventions are working.
Blood Tests for Insulin Resistance - Frequently Asked Questions
What blood tests show insulin resistance?
The most direct tests for insulin resistance are fasting insulin and HOMA-IR (calculated from fasting glucose and fasting insulin). Additional markers that reflect insulin resistance include: fasting glucose, HbA1c, triglycerides, HDL cholesterol, the TG:HDL ratio, ALT and GGT (liver enzymes elevated in fatty liver), and uric acid. No single test is definitive - the pattern across multiple markers gives the clearest picture.
What is the TG:HDL ratio and why does it matter for insulin resistance?
The TG:HDL ratio (triglycerides divided by HDL, both in mmol/L) is a cheap, widely available surrogate marker for insulin resistance and small dense LDL particle concentration. In Australian units (mmol/L), a ratio below 1.0 is optimal; 1.0-1.8 is borderline; above 1.8 suggests likely insulin resistance. Important: this cut-off applies to mmol/L. American guidelines use mg/dL where the same cut-off is around 3.5 - do not confuse the two.
Which of these tests are bulk-billed on Medicare in Australia?
With a valid GP referral, the following tests are typically Medicare bulk-billed: fasting glucose (MBS 66503), HbA1c (MBS 66551), full lipid panel including triglycerides and HDL (MBS 66500), and liver function tests including ALT and GGT (MBS 66500 or similar). The following are private-pay: fasting insulin (~$20-$40), uric acid (~$15-$25 if not included in a panel). Total private cost for a comprehensive insulin resistance panel is typically $35-$65 above the bulk-billed items.
Can you have insulin resistance with a normal fasting glucose?
Yes - this is extremely common. In early insulin resistance, the pancreas compensates by producing 2-5 times more insulin than normal, which keeps fasting glucose in the reference range. The elevated insulin is the problem, not the glucose. This compensatory phase can last years or decades. Measuring fasting insulin directly, or looking for the cluster of high triglycerides, low HDL, and elevated ALT, can reveal insulin resistance long before fasting glucose rises above 5.6 mmol/L.
Is insulin resistance the same as prediabetes?
They overlap but are not the same. Insulin resistance is a physiological state where cells do not respond properly to insulin - it can exist for years with completely normal glucose levels. Prediabetes is defined by specific glucose thresholds: fasting glucose 5.6-6.9 mmol/L or HbA1c 5.7-6.4% (39-47 mmol/mol). Prediabetes almost always involves underlying insulin resistance, but many people with significant insulin resistance do not yet meet the prediabetes glucose threshold. Catching insulin resistance before prediabetes is the goal.
Why is ALT elevated in insulin resistance?
ALT (alanine aminotransferase) is a liver enzyme that leaks into the blood when liver cells are damaged or under stress. In insulin resistance, excess insulin drives fat into the liver (hepatic steatosis, also called metabolic-associated steatotic liver disease or MASLD, formerly NAFLD). The accumulation of fat in liver cells causes low-grade inflammation and cell damage, raising ALT. An ALT above 30-35 U/L (in adults without alcohol use or known liver disease) combined with high fasting insulin and high triglycerides is a strong signal of fatty liver driven by insulin resistance.
How often should I test for insulin resistance markers?
For adults with risk factors (overweight, family history of diabetes, PCOS, high triglycerides, low HDL), a comprehensive metabolic panel including fasting insulin is reasonable every 12-24 months. After lifestyle changes, retesting at 12-16 weeks shows whether intervention is working. The standard Medicare diabetes screen (fasting glucose plus HbA1c) should be done every 1-3 years for adults with risk factors, per Australian RACGP guidelines. The private-pay fasting insulin can be added to any of these blood draws for minimal extra cost.
Related Reading
See Your Full Metabolic Picture in One Place
Upload your blood test PDF and SmarterBlood's AI explains every insulin resistance marker — fasting glucose, triglycerides, HDL, ALT, uric acid — in plain English, flags your TG:HDL ratio, and tracks the trend over time so you can see your metabolic health improving.
This page provides general educational information about blood markers for insulin resistance. Optimal target ranges cited reflect metabolic medicine consensus and may differ from standard lab reference ranges printed on pathology reports. Always discuss results with your GP, who can assess your full clinical picture. SmarterBlood does not provide medical care.