HbA1c and your metabolic health.

What is HbA1c, why it matters and why you should be paying attention to rising numbers. From your clinical nutritionist.

What is HbA1c?

HbA1c (haemoglobin A1c) measures the percentage of your red blood cells that have glucose attached to them.

Red blood cells live for approximately 120 days, this gives us a 3-month snapshot of your average blood sugar levels, not just what happened this morning before your test.

Why it matters?

A single fasting glucose reading only tells you what your blood sugar is doing right now.

HbA1c tells a bigger story. It shows whether your blood sugar has been consistently elevated over time — even if individual readings have looked 'normal.'

Rising HbA1c is one of the earliest signals that your body is struggling to manage glucose effectively.

The ranges.

General ranges:

Below 5.7% (<42 mmol/mol) — considered within the normal range.

5.7–6.4% (42–47 mmol/mol) — classified as pre-diabetes

6.5% or above (≥48 mmol/mol) — diagnostic threshold for type 2 diabetes.

Optimal ranges:

4.1-5.4% or 21-36 mmol/mol

But here's the thing — a reading that's technically 'normal' but steadily creeping upward year on year is already telling you something. Trending matters as much as the number itself.

What drives it up?

Several factors can contribute to a rising HbA1c:

• Excess refined carbohydrates and added sugars

  • White grains, plain potatoes, pastries etc

• Low fibre intake (aim for >30g per day)

• Sedentary lifestyle

• Chronic stress (cortisol directly raises blood glucose)

• Poor sleep (even a few nights of disrupted sleep can impair insulin sensitivity)

• Nutrient deficiencies that affect glucose metabolism

  • Chromium, magnesium, vitamin D

What you can do to lower it.

The good news, HbA1c is responsive to diet and lifestyle changes!

• Build meals around protein, healthy fats, and fibre as these slow the glucose response

• Move your body after meals, even a 10-minute walk makes a measurable difference

• Prioritise sleep and stress management, both directly impact blood sugar regulation

• Ask for the full picture, request fasting insulin alongside fasting glucose and HbA1c, so you and your practitioner can see how hard your body is working to keep glucose in range

A rising HbA1c isn't a diagnosis. It's a signal, and one you can act on early.