What is A1C?
A1C, or glycated haemoglobin, glycosylated haemoglobin, haemoglobin A1C or HbA1c, is a blood test used to diagnose type 1 and 2 diabetes [1]. The test measures the proportion of your haemoglobin proteins coated with sugar (glycated) [1]. Hemoglobin — A protein within red blood cells transports oxygen throughout the body [2].
What Does A1C Do?
The A1C test lists your typical blood glucose (blood sugar) levels in the last three months [3]. It shows your average blood sugar reading over the past two to three months, letting you know exactly how much of the haemoglobin proteins in your blood are sugar (glycated) [1].
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But, to be clear, the A1C test doesn’t capture spikes and dips as a whole, though it does give you an essential overview of your blood sugar stability. This means that even if you’re diabetic, you still must periodically check your blood glucose levels using a fingerstick glucose test [4].
Benefits of A1C
A1C (glycated haemoglobin) is vital in diabetes. It represents the average blood glucose in the previous 2-3 months and gives a snapshot of diabetes management [3].
One of the most significant selling points of the A1C test is that it does not require a fast and can be administered anytime. It is an easy and convenient way to check the blood sugar [4].
Similarly, A1C is useful for monitoring the success of diabetes treatment. For example, continuous glucose monitoring has been shown to reduce A1C and assist patients in maintaining target A1C levels and avoiding biochemical hypoglycemia [5]. Also, a high-intensity lifestyle programme reduces A1C by up to 2.5% in patients with diabetes [6].
Additionally, the A1C test can save money on healthcare expenses. Lower A1C was found to cause a lower rise in healthcare costs after 1–2 years, so interventions that reduce A1C over a relatively short period may save substantial amounts of money [7].
And lastly, the A1C test can evaluate the potential risk of complications. Elevated A1C readings are related to a greater risk of developing diabetic complications, so A1C can be used to prevent and treat such complications [3].
What Do Individuals Expect From an A1C Test?
Their expectation is that the A1C test will reveal their diabetes diagnosis. For example, an A1C of less than 5.7% is expected, 5.7%-6.4% is prediabetes, and 6.5% or higher on two tests is diabetes [1].
Patients also expect the A1C test to indicate their diabetes risk. For instance, people with an A1C of 5.8% or more are at a significantly greater risk of developing poor glucose tolerance or type 2 diabetes within 5 years [8].
Furthermore, patients hope that the A1C test will dictate their treatment regimen. An A1C of less than 7% is an average treatment goal for the majority of adults with diabetes. When someone’s A1C is higher than what it needs to be, their doctor may alter the treatment regimen for diabetes [1].
Lastly, people want to know their A1C results. However, research has shown that patients know past A1C levels but do not compare those values to their control glycemic levels [9].
How Much Can A1C Drop in 3 Months?
The A1C test is a blood test that displays a person’s average blood sugar level over a 2- to 3-month pre-test period [4]. The level at which A1C will decline in 3 months varies from person to person, the type of diabetes, the initial A1C level and the treatment plan.
For type 2 diabetics, oral antidiabetic (OAD) medication reduced A1C levels by 0.5-1.25% throughout 4 to 6 months [10]. When one group of patients had an A1C>9.0%, they experienced a decrease of 0.7% in 3-6 months [11]. One study reported a 0.94 mg/dL boost to haemoglobin after administering vitamin B12 was responsible for a 0.24 drop in HbA1c (%) [12].
Another study demonstrated that CGM lowers average HbA1c for type 1 diabetic patients by 1.1% at 12 weeks [13]. Another analysis found that the highest decrease in A1C with the different types of prandial insulins was 1.3% in the measure of A1C [14].
But, of course, A1C tests provide an average and can't tell us the real spikes and dips alone [4]. Therefore, blood glucose must continue to be measured at regular intervals.