What Your HbA1c Result Means

If you have been told that your HbA1c is high, you may be wondering what that number actually means.

Unlike a blood sugar test taken at one particular moment, HbA1c gives us a longer-term picture of your blood sugar levels.

It is one of the tests I find particularly useful when assessing diabetes and monitoring how well blood sugar is being controlled.

What is HbA1c?

HbA1c is a blood test that looks at how much glucose has attached itself to haemoglobin, a protein found inside your red blood cells.

Because red blood cells circulate for several months, HbA1c gives us an idea of your average blood glucose over roughly the previous 2 to 3 months.

That makes it different from a random or fasting blood sugar.

For example, you may have a normal blood sugar when you visit the clinic today, but if your blood sugar has been consistently high over the previous weeks, your HbA1c may still be elevated.

What does the HbA1c number mean?

HbA1c is commonly reported as a percentage.

In general:

• Below 5.7% is considered normal
• 5.7% to 6.4% is in the prediabetes range
• 6.5% or higher is in the diabetes range

A diagnosis should still be interpreted in the clinical context and, when appropriate, confirmed with repeat or additional testing.

The number is not simply a score. It gives us information about your average blood glucose exposure over time.

Why is HbA1c useful?

Imagine two people.

Person A checks their blood sugar today and gets a normal result.

Person B also checks their blood sugar today and gets a normal result.

From that single reading, both appear fine.

But suppose Person A has generally had normal blood sugar while Person B has had frequent high blood sugar over the past few months.

Their HbA1c results may tell a very different story.

That is the advantage of HbA1c.

It helps us look beyond what is happening on one particular day.

Does HbA1c require fasting?

Usually, no.

Unlike a fasting blood glucose test, HbA1c generally does not require you to fast before the blood sample is taken.

This makes it convenient because the test can generally be performed at different times of the day.

However, if your clinician has requested other blood tests at the same time, you may still be asked to fast depending on those tests.

What if my HbA1c is high?

A high HbA1c generally means that your blood glucose has been higher than it should be over the preceding months.

If you already have diabetes, the result helps us assess how well your current treatment and lifestyle measures are controlling your blood sugar.

If you have not previously been diagnosed with diabetes, a high result may lead to further assessment to determine whether you have diabetes.

The next step depends on the actual result and your clinical situation.

Does a high HbA1c mean I have been eating too much sugar?

Not necessarily.

This is something I would want patients to understand.

Diabetes is more complicated than simply eating sugar.

Blood glucose is affected by insulin production and sensitivity, body weight, physical activity, genetics, illness, medications and overall dietary patterns, among other factors.

So I would not look at an elevated HbA1c and simply tell someone that they "eat too much sugar."

The important thing is to understand what is driving the elevated blood glucose and what can realistically be changed.

What HbA1c target should someone with diabetes have?

There is no single HbA1c target that is appropriate for every person with diabetes.

The target may depend on factors such as:

• Age
• Duration of diabetes
• Other medical conditions
• Risk of low blood sugar
• Pregnancy
• Current treatment
• Ability to safely follow the treatment plan

For many non-pregnant adults with diabetes, a target around 7% is commonly used, but individual targets may be higher or lower.

The goal is good control without creating unnecessary risks, particularly hypoglycaemia.

Can HbA1c be too low?

Lower is not automatically better.

If someone is taking medication that can cause low blood sugar, aggressively lowering glucose may increase the risk of hypoglycaemia.

Symptoms of low blood sugar can include:

• Sweating
• Shaking
• Hunger
• Dizziness
• Confusion
• Weakness
• Palpitations

Severe hypoglycaemia can cause loss of consciousness or seizures.

This is why treatment targets should be individualized rather than simply trying to achieve the lowest possible HbA1c.

Can HbA1c sometimes be misleading?

Yes.

HbA1c depends on red blood cells and haemoglobin, so conditions that affect them can sometimes make the result less reliable.

Examples include certain forms of anaemia, blood loss, recent blood transfusion and some haemoglobin disorders.

Kidney disease and other medical conditions can also affect interpretation.

This is why I don't interpret an HbA1c result in isolation when the clinical picture does not make sense.

If your HbA1c does not seem to match your home glucose readings or symptoms, tell your clinician.

Sometimes another method of assessing glucose may be more appropriate.

HbA1c versus fasting blood sugar

These tests answer slightly different questions.

Fasting blood glucose tells us what your blood glucose is at a particular time after fasting.

HbA1c gives us a longer-term picture of average glucose exposure.

For example, someone can have a normal fasting glucose but an elevated HbA1c.

That is why both tests can be useful depending on the situation.

How often should HbA1c be checked?

The frequency depends on your situation.

Someone whose diabetes is stable may not need testing as frequently as someone who has recently changed treatment or whose blood sugar is not well controlled.

Your clinician can determine an appropriate testing interval based on your treatment and glucose control.

What can I do if my HbA1c is high?

The answer depends on why it is high.

Possible steps include:

• Reviewing your diet
• Increasing appropriate physical activity
• Reviewing your medications
• Taking prescribed medication consistently
• Monitoring blood glucose when advised
• Managing body weight where appropriate
• Addressing other cardiovascular risk factors
• Following up regularly with your healthcare team

Do not stop diabetes medication because your HbA1c has improved.

The improvement may actually be evidence that the treatment is working.

What I want patients to remember

HbA1c is not a measure of how "good" or "bad" you have been.

It is a clinical measurement that helps us understand what your blood glucose has been doing over time.

If the result is high, the useful question is not simply:

"Why did I fail?"

It is:

"What is causing my blood sugar to remain high, and what can we do about it?"

That is where proper assessment and a realistic treatment plan come in.

The bottom line

HbA1c gives us a picture of your average blood glucose over roughly the previous 2 to 3 months.

It is useful for diagnosing diabetes in appropriate circumstances and monitoring glucose control in people who already have diabetes.

A result of 6.5% or higher is in the diabetes range, while 5.7% to 6.4% is generally considered the prediabetes range.

But don't interpret the number alone.

Your age, medical conditions, medications and other factors all matter.

If you have an HbA1c result you do not understand, take the actual number to your clinician and discuss what it means for you.