Insulin resistance moves quietly for ten to fifteen years before HbA1c flags it. By then, much of the damage is set: visceral fat, fatty liver, vascular stiffening, and a pancreas working overtime. The earlier markers exist. Most NZ GP panels do not run them by default.

The short answer

Standard NZ blood panels catch insulin resistance late. Fasting glucose and HbA1c only rise once the pancreas can no longer compensate. Before that point, insulin is already elevated, triglycerides are climbing, and HDL is dropping. Three markers tell you the story years earlier: fasting insulin, HOMA-IR, and the triglyceride-to-HDL ratio. You can request these. We work alongside your GP to interpret them in context.

Why HbA1c misses the early window

HbA1c measures average blood glucose over roughly three months. It only shifts once your pancreas stops producing enough insulin to overcome resistance at the cell level.

For a decade or more before that, the pancreas compensates. It pumps out two, three, sometimes five times the normal insulin to keep glucose in range. Glucose looks fine. HbA1c looks fine. The patient is told they are healthy. Meanwhile, chronic hyperinsulinaemia is driving fat storage, suppressing fat oxidation, and quietly damaging the endothelium.

This is the window where intervention is cheapest and most effective. It is also the window most people miss.

The three markers worth requesting

Fasting insulin. A direct measure of how hard your pancreas is working at rest. Optimal sits in the 3 to 6 mIU/L range. Lab "normal" often runs to 25. A fasting insulin of 15 with normal glucose is not reassurance. It is a warning.

HOMA-IR. Calculated from fasting insulin and fasting glucose. The formula: (fasting insulin x fasting glucose) / 22.5, using mmol/L for glucose. Below 1.0 is excellent. Above 1.5 suggests resistance. Above 2.5 is significant. It is a single number that captures what HbA1c cannot.

Triglyceride-to-HDL ratio. Pulled from a standard lipid panel, so most NZ adults already have the data. Divide triglycerides by HDL (both in mmol/L). Below 0.87 is good. Above 1.5 correlates strongly with insulin resistance and small-dense LDL particles. It is the cheapest proxy available, and it is sitting in your last GP results.

What the markers actually tell you

Fasting insulin shows current pancreatic load. HOMA-IR shows the relationship between that load and your glucose response. The triglyceride-HDL ratio reflects what insulin resistance is doing to your liver and lipid metabolism.

Together they form a picture. One marker can mislead. Three rarely do.

If your fasting glucose is 5.2, your HbA1c is 36, and your fasting insulin is 18, you do not have a clean metabolic profile. You have a pancreas working five times harder than it should to produce that "normal" glucose reading.

In our coaching work, we see this pattern constantly. Clients arrive with a clean GP report and a body that tells a different story: stubborn waist fat, afternoon energy crashes, poor sleep, slow recovery. The BIA scan shows elevated visceral fat. The bloods, once we look at the right numbers, confirm it.

What moves these markers

The literature is consistent on what works. So is what we see across 1,380+ clients.

Protein intake at 1.6 to 2.2 g/kg of lean mass improves satiety, preserves muscle during fat loss, and reduces the glycaemic load of meals. Most NZ adults eat half this.

Resistance training two to four times per week increases GLUT4 expression in muscle, the non-insulin-dependent glucose uptake pathway. Muscle is the largest sink for blood glucose. More muscle, more capacity, less insulin required.

Walking after meals, even ten minutes, blunts the post-meal glucose spike and reduces the insulin response. It is the highest return-per-minute intervention in metabolic health.

Sleep below seven hours raises fasting insulin within a week. This is measurable and reversible.

Carbohydrate quality matters more than quantity for most people. Kūmara, oats, fruit, and legumes behave differently to bread, crackers, and muesli bars, even at matched grams. Fibre, food matrix, and meal context all change the insulin response.

Visceral fat loss, specifically, drives the largest improvements in HOMA-IR. This is why BIA scanning matters: scale weight does not distinguish between subcutaneous and visceral loss, but the metabolic outcome depends on which one moves.

The NZ context

GP visits in New Zealand are short. Standard metabolic screening covers HbA1c, fasting glucose, and a lipid panel. Fasting insulin is not on the default request form. You can ask for it. Some GPs will run it readily, others will push back on cost or relevance.

If you are over 35, carrying central fat, or have a family history of type 2 diabetes, the case for fasting insulin is strong. The test is inexpensive. The information it gives, paired with HOMA-IR, is the difference between catching insulin resistance with a decade of runway and catching it once the diagnosis is already written.

Bring the request to your GP. We work alongside them on interpretation and on the lifestyle work that moves the numbers.

What to do this week

  • Pull your most recent lipid panel and calculate your triglyceride-to-HDL ratio.
  • Book a GP appointment and request fasting insulin alongside your next fasting glucose.
  • Add a ten-minute walk after your largest meal of the day, every day.
  • Audit your protein intake for three days. Aim for 1.6 g per kg of lean mass minimum.
  • If you are not training against resistance twice a week, start. Bodyweight counts.

Insulin resistance is a slow problem with an early signature. Read the signature. Act in the decade where the work is cheap.