HbA1c blood tests and type 1 diabetes
Most people are aware that type 1 diabetes (T1D) management involves closely monitoring blood glucose levels. But there’s another test you may have heard of: the haemoglobin A1c (HbA1c) test.
Here’s what you need to know about HbA1c and how it’s tested, as well as other important tests for people living with T1D.
What is HbA1c?
When you check your blood glucose level (BGL) with a blood glucose meter (finger pricks), continuous glucose monitor (CGM) or flash glucose monitor (flash GM), you’re measuring how many molecules (or mmol) of glucose are in your blood stream right then.
The glucose in your blood stream attaches itself to the haemoglobin part of your red blood cells – and that’s what’s called glycated haemoglobin, or HbA1c. If there’s a lot of glucose in your blood stream, this will result in a higher number of haemoglobin with glucose attached.
What is the HbA1c blood test?
As your blood cells (and therefore your haemoglobin) live for around 120 days, your HbA1c result looks at your overall blood glucose levels for the preceding two to three months.
The HbA1c test is a blood test, and your doctor or diabetes team might arrange for you to have it for a number of reasons, including:
- ongoing diabetes management. It’s important to schedule an HbA1c test at least twice a year, and perhaps more frequently if your results aren’t optimal, or if your medication or health conditions change. Chat with your doctor to figure out your ideal testing frequency.
- testing for prediabetes or diagnosis of diabetes. If you’re experiencing symptoms of type 1 or type 2 diabetes, your doctor might suggest an HbA1c test to confirm a diagnosis.
- during pregnancy. HbA1c tests are increasingly being used to monitor for gestational diabetes and to detect elevated HbA1c in pregnant people living with type 1 diabetes, which is associated with maternal-foetal complications.
HbA1c measurements can be reported as percentages (HbA1c as a percentage of total haemoglobin) or the scientific unit of mmol/mol (millimoles HbA1c per mole of total haemoglobin). Medicare offers a subsidy, allowing you to have the test up to four times within a year.
HbA1c and diabetes diagnosis
The HbA1c test is one of the most comprehensive tests available for type 1 diabetes diagnosis.
When it comes to diagnosing diabetes, healthcare experts recommend using an HbA1c level of 6.5% (7.8mmol/L) as the target. However, it’s important to note that having a value below 6.5% doesn’t necessarily rule out diabetes that was diagnosed using glucose tests. It’s always best to consult with your doctor for a comprehensive understanding of your specific situation.
Read about other tests for diagnosing type 1 diabetes here.
What is a normal HbA1c level?
When it comes to A1C levels:
- below 5.7% (39mmol/mol) is considered normal
- a range of 5.7% (39mmol/mol) to 6.4% (46mmol/mol) indicates prediabetes
- a value of 6.5% (48mmol/L) or higher suggests diabetes.
If your A1C falls within the prediabetes range, remember that the higher it is, the greater your risk of developing type 2 diabetes.
What HbA1c result should I aim for?
It’s recommended that adults living with type 1 diabetes aim to keep their HbA1c as close to 53mmol/mol (or 7%) as possible, as long as this can be achieved without significant episodes of hypoglycaemia.
Research has shown that keeping your HbA1c near this goal can significantly reduce your risk of developing the long-term complications of diabetes. In a recent study, researchers found that individuals with an HbA1c level of 7% or higher had a higher risk of developing retinopathy and early kidney disease compared to those with levels between 6.5% and 6.9%. The risk escalated for those with an HbA1c of 8.6% or higher.
Over time, your targets may need to change, so make sure you discuss what your target should be with your diabetes team.
HbA1c conversion chart from HbA1c % to system international (SI) units
|HbA1c (%)||HbA1c (mmol/mol)|
What about time in range (TIR)?
Now that CGM technology has made it possible to check your blood glucose levels around the clock, you may have heard people talking about time in range (TIR). TIR is a measurement that lets you know what percentage of the day your blood glucose levels are in your goal range. You might also hear TIR referred to as the hours per day spent in range.
You’ll work with your healthcare team to clarify what your own personal goal range is, but the general recommendation is between 3.9-10.0 mmol/L (while also checking the amount of time you spend with very low glucose levels, or hypoglycaemia).
The more time you spend in range, the lower your chance of developing certain diabetes complications.
When it comes to managing type 1 or type 2 diabetes, it’s generally recommended you aim for a TIR of over 70%. That means spending approximately 17 out of 24 hours in a day within the target blood glucose range.
How is TIR different from your HbA1c test?
While HbA1c results tell you your average glucose level over the past two or three months, they won’t show how much time you spent in hypoglycaemia or hyperglycaemia, or if your levels are often bouncing from high to low.
Your HbA1c gives you an estimate of the middle of your range, but your TIR gives much more insight into daily patterns and how your average glucose level is formed.
Learn more about time in range with Diabetes Australia.
Other regular health checks for people living with T1D
You may be surprised that endocrinologists and GPs don’t just focus on the blood glucose levels or HbA1c levels of people living with T1D. Optimum T1D management also requires a focus on other tests, including blood pressure and cholesterol levels, because the risk of diabetes-related complications is reduced when blood glucose levels, blood pressure and blood fats are kept as close to normal as possible.
- Have your blood pressure checked regularly (at every visit to the doctor) and treated if necessary. For someone with diabetes, the target blood pressure reading is 130/80mmHg or lower.
- Have your cholesterol checked every year. The target for total cholesterol is 4mmol/L, with target LDL (bad) cholesterol of <2mmol/L; HDL (good) cholesterol >1mmol/L and triglycerides of <1.8mmol/L.
Goals for optimal type 1 diabetes health management
There are many considerations and measurements your diabetes healthcare team will keep in mind to help guide your treatment plan and achieve healthy outcomes. Here’s an outline.
|Body mass index (BMI)||<25kg/m2 where practicable|
|Cholesterol – HDL||>1.0mmol/L|
|Cholesterol – LDL||<2.0mmol/L|
|Cholesterol – total||<4.0mmol/L|
|HbA1c||≤53mmol/mol or 7%|
|Physical activity||At least 30 minutes walking (or equivalent), five or more days/week (total ≥150 minutes/week)|
|Urinary albumin excretion||<20g/min (timed overnight collection); <20mg/L (spot collection); <2.5mg/mmol: men (albumin creatinine ratio); <3.5mg/mmol: women (albumin creatinine ratio)|
Source: Diabetes Australia, Diabetes Management in General Practice 15th Edition
Managing diabetes, especially type 1 diabetes, involves understanding key aspects like HbA1c tests, time in range (TIR), and regular health checks. Work closely with your healthcare team to set goals and achieve a healthier life with diabetes.
- All about your A1C (Centers for Disease Control and Prevention)
- Association between HbA1c levels on adverse pregnancy outcomes during pregnancy in patients with type 1 diabetes (Journal of Clinical Endocrinology & Metabolism)
- Gestational diabetes mellitus (Australian Journal of General Practice)
- Glycated haemoglobin (HbA1c) for the diagnosis of diabetes (World Health Organization)
- HbA1c (Australian Journal of General Practice)
- HbA1c and monitoring glycaemia: What do I tell my patient? (RACGP)
- HbA1c level as a risk factor for retinopathy and nephropathy in children and adults with type 1 diabetes: Swedish population based cohort study (BMJ)
- HbA1c test (Health Direct)
- Hemoglobin A1c (HbA1c) test for diabetes (WebMD)
- Medicare Benefits Schedule
- Study suggests new HbA1c “sweet spot” to reduce risks of complications in type 1 diabetes (JDRF UK)
- The role of HbA1c in the diagnosis of diabetes mellitus in Australia (Medical Journal of Australia)
- Time-in-range and diabetes (Endocrine Society)
- Time in range is an important tool (Diabetes Australia)