HbA1c vs Insulin: Are We Measuring the Same Thing?

Two different measurements

You may have been told that your HbA1c is normal and assumed this means your metabolic health is optimal. But HbA1c and insulin do not measure the same thing.

Understanding the distinction can be useful — particularly when we are thinking proactively about metabolic health rather than simply asking whether someone has reached the diagnostic threshold for diabetes.

What does HbA1c measure?

HbA1c measures glycated haemoglobin. In simple terms, it gives us an indication of your average blood glucose over approximately the previous two to three months.

It is an established and extremely useful test for diagnosing and monitoring type 2 diabetes in appropriate patients.

In the UK, an HbA1c of 42–47 mmol/mol is generally classified as non-diabetic hyperglycaemia or high risk of developing diabetes, while 48 mmol/mol or above is within the diabetic range. An abnormal result may need confirmation depending on symptoms and circumstances.

What does insulin measure?

Insulin is a hormone produced by the pancreas. Its job is to help glucose move from the bloodstream into cells, where it can be used or stored for energy.

As insulin sensitivity decreases, the body may compensate by producing more insulin to maintain glucose within a relatively normal range. This means glucose and insulin are related — but they tell us different things.

Can you have a normal HbA1c and raised insulin?

Potentially, yes. Someone's body may be producing sufficient insulin to keep their glucose within a normal range despite reduced insulin sensitivity.

However, a fasting insulin level is not a replacement for HbA1c, and fasting insulin or calculations such as HOMA-IR are not standard diagnostic tests for diabetes. There is also no single fasting insulin threshold that should be applied universally to diagnose insulin resistance.

So should everyone have their insulin checked?

No. More testing does not automatically mean better healthcare.

For established diabetes screening and diagnosis, HbA1c and/or glucose testing remain the validated clinical tools. Fasting glucose and insulin may provide additional metabolic information in selected patients, but results need to be interpreted alongside weight, waist circumference, blood pressure, lipids, family history, medications and other clinical factors.

Looking at metabolic health as a whole

At Family Doctor Group, proactive health is not about chasing every biomarker into an arbitrary “optimal” range. It is about identifying meaningful risk factors early and deciding whether there is something useful we can do about them.

Our proactive health assessments can include HbA1c, fasting glucose, lipids and other metabolic and cardiovascular markers, with additional testing selected according to your individual history.

Enquire about an appropriate consultation at Family Doctor Group in Epsom or Esher.