You have a test and see the result HbA1c 5.8%, while your blood glucose that day was still normal. So is it something to worry about?
HbA1c is a test that reflects your average blood glucose level over the past 2–3 months. Unlike a blood glucose test taken at a single moment, HbA1c lets the doctor see a longer-term blood glucose trend.
This test is often used to help detect prediabetes and type 2 diabetes and to monitor blood glucose control in people who have already been diagnosed.
What HbA1c level is normal?
According to the CDC and the American Diabetes Association:
HbA1cMeaning
Below 5.7%
Normal
5.7% – 6.4%
Prediabetes
≥6.5%
Diabetes diagnostic threshold
For example:
HbA1c 5.4%
→ falls within the normal range.
HbA1c 6.0%
→ falls within the prediabetes range.
HbA1c 6.7%
→ reaches the test threshold used to diagnose diabetes.
However, an HbA1c result of ≥6.5% is not always enough on its own to conclude that you have diabetes. In many cases, the doctor will need to confirm it with a repeat test or another blood glucose test, particularly if you have no clear symptoms.
Why is HbA1c different from fasting blood glucose?
The two tests look at blood glucose health in two different ways.
Fasting blood glucose
Shows the amount of glucose in the blood at the moment the sample is taken after a period of fasting.
The result can vary from day to day depending on the meal beforehand, physical activity, stress or your state of health.
HbA1c
Shows the blood glucose trend over the past few months so it is less affected by a single meal or by one day when blood glucose rises temporarily.
So it is perfectly possible for someone to have:
Normal blood glucose today but a high HbA1c.
The two results are not necessarily contradictory. The doctor may need to look at them together to understand your blood glucose situation more clearly.
Does HbA1c show how much blood glucose rises after eating?
Not fully.
HbA1c is a long-term average value. It does not tell you exactly:
- What your blood glucose was this morning
- How high it rose after eating
- Whether you have ever had low blood glucose
- How widely your blood glucose swings during the day
Two people with the same HbA1c of 6.5% can still have very different patterns of blood glucose fluctuation.
So in people who already have diabetes, the doctor may need to combine HbA1c with blood glucose measurements at home or with a glucose monitoring device, depending on the case.
When should you have your HbA1c checked?
Your doctor may suggest a test if you have risk factors for prediabetes or type 2 diabetes.
You should speak to your doctor in particular if you have:
- A family history of diabetes
- Overweight or obesity
- Little physical activity
- High blood pressure
- A lipid disorder
- A history of gestational diabetes
- Blood glucose that has been raised before
- Unusual thirst or passing urine frequently
- Unintentional weight loss
Many people at the prediabetes stage have no clear symptoms, so testing can help detect the risk earlier.
What if your HbA1c is 5.7–6.4%?
This range is classed as prediabetes.
That does not mean you will definitely develop type 2 diabetes.
But the risk is already higher than normal, and within that 5.7–6.4% range, the higher the HbA1c, the greater the risk of progressing to diabetes.
This is the moment to pay attention to:
- Diet
- Physical activity
- Weight
- Sleep
- Blood pressure
- Lipid profile
- A re-testing schedule as advised by your doctor
Do not wait until your HbA1c reaches 6.5% before you start making changes.
What HbA1c is good if you already have diabetes?
There is no single target that is the same for everyone.
For many people with diabetes, the target is usually set around 7% or lower, but the doctor may adjust it according to your age, your risk of low blood glucose, how long you have had the condition, cardiovascular disease, kidney disease and other health problems.
So:
A lower HbA1c is not always better.
The target needs to be low enough to reduce the risk of complications while still being safe for each individual.
When might HbA1c not be accurate?
HbA1c depends on red blood cells and haemoglobin, so some conditions can make the result higher or lower than it really is.
For example:
- Severe anaemia or iron deficiency
- Recent blood loss
- Blood transfusion
- Some haemoglobin disorders such as thalassaemia
- Kidney disease
- Liver disease
- Certain stages of pregnancy
If your HbA1c and your other blood glucose results do not match, the doctor may need to assess the cause or use a different test.
The simplest way to read HbA1c
You only need to remember three thresholds:
<5.7% → Normal
5.7–6.4% → Prediabetes
≥6.5% → Diabetes diagnostic threshold
But do not stop at a single number.
Also look at:
- What was your previous result?
- Is your HbA1c rising or falling?
- What is your fasting blood glucose like?
- Do you have any other risk factors?
A single result tells you about one moment in time. Only the trend across several tests helps you see clearly which way your blood glucose is changing.
Tracking HbA1c and your health on Halza
Through Halza, you can store test results and health records so they are easy to look back at when you need them.
Tracking HbA1c across several checks makes it easier to see whether the figure is rising, falling or staying stable, instead of looking at a single isolated result.
Do not only ask “What is my HbA1c?”. Also ask: “How is it changing over time?”
The information in this article is for reference only and does not replace a doctor's advice, diagnosis or treatment. A diagnosis of prediabetes or diabetes must be made by a healthcare professional based on appropriate tests and on each person's individual situation.
Frequently asked questions
What is HbA1c?
HbA1c is also known as A1C, haemoglobin A1c or glycated haemoglobin.
Glucose in the blood can attach to haemoglobin – a protein inside red blood cells. When blood glucose stays at a higher level for a long time, the proportion of haemoglobin with glucose attached also increases.
HbA1c measures this proportion and it is expressed as a percentage (%).
Do you need to fast for an HbA1c test?
No.
You can eat and drink normally before having an HbA1c test. This is one of the differences from the fasting blood glucose test, which usually requires fasting for at least 8 hours.
Is HbA1c exactly your average blood glucose over 3 months?
It can be understood simply in that way, but not quite as an “even split across 3 months”.
HbA1c reflects blood glucose over about 2–3 months, however blood glucose levels in the most recent 30 days affect the result more than the months before that.
So HbA1c shows a long-term blood glucose trend rather than a simple average of each individual day.
References
- NIDDK – The A1C Test & Diabetes
- CDC – A1C Test for Diabetes and Prediabetes
- American Diabetes Association – Diabetes Diagnosis
- NIDDK – Diabetes Tests & Diagnosis
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