Insulin resistance: what you can discuss at the practice

Most of it is already there

The commonest misconception on this topic is the assumption that a whole series of exotic tests is needed. In fact a normal routine panel already contains four of the five building blocks required for an assessment of insulin resistance: fasting glucose, HbA1c, triglycerides and HDL cholesterol.

From two of them the TyG index can be calculated, from two others the ratio of triglycerides to HDL. Both count as usable approximations for insulin sensitivity, and both cost nothing extra – the numbers are already there.⁴

So anyone digging out their last laboratory report already has a starting point. That is the simplest first step and costs nothing but a look through the paperwork.

The one value that is usually missing

Fasting insulin is not part of every standard panel. Yet it is the only value that answers the actual question directly: how much insulin does the body need for its current blood sugar? Without it, no HOMA-IR can be calculated either.

On the question of cost, in general terms: with a documented indication – such as metabolic syndrome, fatty liver or PCOS – statutory insurers often cover the measurement. Whether that applies in an individual case is decided by the practice, and handling differs. As a self-funded test, an insulin measurement sits in a manageable range.

The most important limitation that hardly anyone mentions

Here comes a point that popular accounts almost always omit and that matters precisely for people with established type 2 diabetes: HOMA-IR can come out falsely normal in diabetes.

The reason lies in how it is calculated. HOMA-IR assumes that the pancreas answers insulin resistance with more insulin. If beta-cell function is already impaired, that answer is weaker – insulin in the blood is lower, and the calculated index looks better than the situation actually is.²

In practice this means: an unremarkable HOMA-IR in established diabetes is no reason for reassurance. And a falling HOMA-IR over time can mean two completely different things – better insulin sensitivity, or declining insulin production. Telling those two apart is precisely the task that requires a medical assessment.

What HOMA-IR is not

It is not a diagnostic criterion. The recognised criteria for prediabetes and diabetes are HbA1c, fasting plasma glucose and the oral glucose tolerance test.⁵ HOMA-IR adds to that picture; it does not replace it.

For orientation, laboratories typically give: up to about 1 unremarkable, 1 to 2 a grey zone, above 2 a sign of insulin resistance or fatty liver, above 2.5 insulin resistance being very likely.³ These boundaries are orientation, not diagnosis – studies work with different thresholds, and insulin measurement is less standardised between laboratories than glucose or HbA1c.

Four questions that open the conversation

The trickiest part is not technical but interpersonal. Anyone arriving at the practice with a printed list from the internet and demanding investigations rarely gets the best conversation. Anyone bringing a concrete question usually does.

I consider the fourth question the most important: what would tell you that something has improved? It reverses the direction of view. Instead of collecting and interpreting values yourself, you ask for the criterion – and get something that applies to your own case rather than to a study average.

What else is worth asking about

Besides blood values there are two investigations often relevant to insulin resistance that can be raised.

• Keep an eye on liver values. ALT and GGT are usually on the report anyway. Raised values can indicate a fatty liver – and that plays a central role in insulin resistance.
• An ultrasound of the liver. It shows fatty change that blood values do not always reveal. Not routine for everyone, but an obvious step where there is a corresponding suspicion.
• Waist circumference. Costs nothing, takes a minute and says more about visceral fat than body weight does. It can be tracked at home.
• Blood pressure over time. It belongs to the same picture and often changes in parallel with insulin sensitivity.

How to validate results later

For tracking a course the same holds as for any measurement: comparability beats precision. Four points make the difference between a series of numbers and a conclusion.

And one point that follows from the physiology: measuring too early means measuring too early. The liver responds within days, the pancreas needs weeks to months.⁶ A check after four weeks can therefore disappoint although everything is on track.

Why the timing of the draw matters

Fasting insulin varies more than most other laboratory values. It responds to the evening before, to sleep, to stress – and to exercise. Anyone who trained hard the previous day measures a value shaped by the acute training effect rather than by the baseline.

That is no reason to skip training, but a reason to place the draw deliberately. A two-day gap from the last intense session makes two measurements considerably more comparable. Anyone training regularly does best to choose the same weekday with the same gap every time – then at least the training effect stays constant.

The same holds for the evening before. A fatty late meal reaches into the morning. For tracking a course, a normal, unremarkable evening is a better starting point than a particularly disciplined one – because what should be captured is everyday life, not a special case.

What belongs in the record so it is still useful later

A practical note that often becomes apparent only when it is too late: reports accumulate, and after two years nobody remembers the circumstances under which a value arose.

It pays to note three things with every report – date, laboratory and the circumstances. Such as: how long fasted? When was the last training session? Were there particulars such as illness, heat or a short night? Those three lines later decide whether a comparison is possible at all.

Anyone working digitally does best to keep a small table: date, fasting glucose, fasting insulin, triglycerides, HDL, HbA1c – and the calculated values alongside. Then the direction is visible at a glance instead of hunting through old letters each time.

What to expect realistically

Not every practice will want to measure fasting insulin, and there are substantive reasons for that. The value is not part of the diagnostic criteria, it is less standardised than glucose, and with established diabetes its informative value is limited. A refusal is therefore not obstruction but often a reasoned judgement.

If that is the case, plenty remains: the TyG index and triglyceride-to-HDL can be calculated from values measured anyway. Both serve for tracking a course, and both cost nothing extra. That is no substitute for HOMA-IR, but it is considerably more than nothing.

A word on self-test kits from the internet

There are now providers who post out blood tests for self-collection, some with fasting insulin in the package. That sounds convenient but has two catches worth knowing.

The first is technical: insulin is not particularly stable in blood. Little time should pass between collection and processing, and the sample should stay cool. Shipping over two days is not ideal for that, and providers handle it differently.

The second weighs more heavily: a laboratory value without interpretation is a number, not a finding. Anyone seeing a raised value on screen with nobody to place it in their own context mainly gains uncertainty. The same value via the practice may cost little more and comes with the thing that makes it useful in the first place.

The honest closing thought

Laboratory values are useful, but they are not progress itself. They are a snapshot, taken on one morning, with one particular method. What they can do: show a direction when followed over months under matching conditions. What they cannot do: answer whether you are on the right path – that needs somebody who knows the whole case.

The best way to handle it is unspectacular: dig out the last report, bring one concrete question, repeat the same thing in a few months. That is less exciting than a hunt for numbers, but it is what eventually turns into a reliable conclusion.