HbA1c is useful – but it misses a lot. Here are the blood sugar markers that reveal insulin resistance, post-meal dysregulation and metabolic dysfunction years before they show up on a standard test.
What is HbA1c – and what does it actually measure?
HbA1c shows your estimated average blood sugar levels over the last 3 months; in the simplest terms, it is how much sugar has attached itself to the haemoglobin in your red blood cells, which is why it has some value for screening and monitoring.
In the UK, HbA1c is usually reported in mmol/mol. A result of 41 mmol/mol or below is generally considered normal, 42-47 mmol/mol falls into the prediabetes range, and 48 mmol/mol or above is in the diabetes range if confirmed on repeat testing.
Spotting these shifts early really matters because steadily rising blood sugar is the road that leads towards type 2 diabetes, and it is often a road you can step back from with the right changes.
The four main ways HbA1c misses the real picture
- HbA1c is an average. That means it can hide big swings between high spikes and low dips. Two people can have the same HbA1c while having very different daily glucose patterns
- It misses post-meal spikes and drops that follow. You can have a normal HbA1c and still see sharp rises in glucose after eating, and then the crashes that lead to cravings, fatigue and brain fog.
- HbA1c can be distorted by conditions that affect red blood cells, including anaemia. If red cell turnover is altered, the number may be less reliable as a reflection of true glucose exposure.
- HbA1c can lag behind the process. Insulin resistance often develops years before glucose markers cross the usual cut-offs, which means someone can appear “normal” on HbA1c while metabolic dysfunction is already underway.
Fasting insulin: the test your GP probably didn’t order
Fasting insulin actually tells you how hard your pancreas, where insulin is made, is working to keep blood glucose levels under control, i.e. not too high. It tells you how much insulin needs to be released into your blood to ensure that blood glucose levels don’t rise dangerously high. It is measured after an overnight fast so that the result is not impacted by what you have eaten, when insulin levels will naturally be much higher. It is one of the most useful early markers for insulin resistance.
In general, lower fasting insulin is considered to be more favourable; an approximate optimal range is 2-10 mIU/L, though laboratory ranges vary. Below 8 mlU/L is considered to reflect high insulin sensitivity and good metabolic health. However, results should be interpreted using the reference range provided by the testing laboratory alongside clinical history and symptoms.
If you have symptoms of insulin resistance (unexplained fatigue, crashing energy soon after meals, intense cravings and/or hunger, brain fog, disturbed sleep, weight-gain, more frequent urination) then fasting insulin is one of the first tests to request alongside fasting glucose, and it can be especially helpful when HbA1c is still normal. However, you will not be able to request this test via your NHS GP, if you have private health insurance you may be able to request it.
If you are not sure whether fasting insulin is worth testing, you can book a free call and we will help you work out which markers are actually useful for you.
HOMA-IR: calculating your insulin resistance score
HOMA-IR stands for Homeostatic Model Assessment of Insulin Resistance. Fasting glucose and fasting insulin are combined into a single score that gives a more robust measure of the amount of insulin needed to maintain blood sugar in a safe range.
A commonly used formula is HOMA-IR = (fasting glucose (mmol/L) × fasting insulin (µIU/mL) / 22.5. Lower scores generally indicate better insulin sensitivity, while higher scores indicate greater insulin resistance.
Because HOMA-IR uses both glucose and insulin, it can reveal early dysfunction even when each marker on its own still looks ‘fine’.
Fasting glucose vs post-meal glucose – why both matter
Fasting glucose tells you what your blood sugar looks like after not eating overnight. Post-meal glucose shows how well your body handles a real-world meal, which is often where early problems appear first.
A fasting glucose test may not capture all factors affecting blood sugar control, so a 2-hour oral glucose tolerance test (OGTT) can help uncover issues a fasting test may miss. In some settings, a continuous glucose monitor (CGM) can give an even richer picture of how food, sleep, exercise, and stress affect your glucose day to day. As a general rule, blood sugar should be back down close to baseline two hours after eating, rather than staying elevated for long periods. If glucose remains high at the 2-hour mark, it may suggest poorer glucose handling and warrant further assessment.
What continuous glucose monitors (CGMs) reveal that blood tests can’t
A CGM doesn’t just give you a snapshot – it shows the pattern. That means you can see how different meals, stress, poor sleep, alcohol, exercise, and fasting affect your glucose in real time.
This can be especially useful if you’re not diabetic but suspect you may be getting glucose spikes, energy crashes, cravings, or reactive dips after meals. For some people, that pattern is the missing piece that standard bloodwork never shows.
We may suggest that a client use a CGM for 2 weeks to track glucose trends, which we can then use to guide them in improving with simple, easy-to-implement dietary and lifestyle changes.
It can be the turning point – see how one of our clients dropped 6kg, banished brain fog and reclaimed her energy on our That Blood Sugar Fix® programme, once she could finally see what her glucose was doing.
How to get a better metabolic picture – NHS and privately
If you’re speaking to your GP, it’s reasonable to ask whether fasting glucose and HbA1c are appropriate, and whether there’s any reason to check for iron deficiency anaemia or other factors that could affect interpretation. You can also ask whether fasting insulin levels or further glucose testing is clinically appropriate, although this isn’t routinely offered.
If you’re testing privately in the UK, a broader metabolic panel often includes HbA1c, fasting glucose, fasting insulin, and sometimes an OGTT or CGM access depending on the provider. Private pricing varies by provider and package, so it’s worth comparing what is actually included rather than just looking at the headline price, and we guide our clients accordingly.
How Integral Wellness uses the full testing picture with clients
At Integral Wellness, we look beyond a single marker to build a fuller picture of metabolic health. That means considering HbA1c alongside fasting insulin, fasting glucose, and post-meal patterns so we can spot issues earlier and support clients with a more personalised plan.
Blood sugar is only one part of that picture. The same insulin resistance that shows up in these markers also shapes your cholesterol, which is why the two are best understood together.
If you want to understand what is happening inside more clearly, you can download our free Cholesterol Explained guide, book a one off wellness check, or arrange a free call with us.
This is often the point where people stop guessing and start seeing what their body is actually doing.
