The HbA1c, often just called an A1C (aye-one-see), is a blood test that can give us an idea of your body’s average blood sugar over the last couple of months. Sometimes the test is sent to a lab along with other routine blood tests, and other times it may be done at the doctor’s office using a fingerstick sample.
The purpose of the test is to get some idea of how well controlled your diabetes is, and to make sure your blood sugars are not at dangerous levels.
Here’s how it works: red blood cells are like the FedEx trucks of your body. They shuttle packages of oxygen and carbon-dioxide around from your lungs to your cells and back again. Your blood stream is the highway these “trucks” drive on. Now let’s pretend that it’s winter. If the roads are muddy and icky, the trucks are going to get dirty.
In your body, sugar molecules stick to the skins of red blood cells just like the dirty slush of winter roads stick to the white trucks, making them dirty.
The percentage of the skin of the blood cells covered in sugar give us the A1C score. For most diabetics a score between 6.0 and 6.9 is considered in good control. For perspective, kidney damage can start at scores over 9.0 while non-diabetics are typically under 5.0 percent.
Now, you might wonder why you need this test if you are checking your blood sugar with a meter at home, and the simple answer is that it is a great way to double check that the meter is working right and that you aren’t missing something. For instance, let’s just say you check your blood sugar first thing in the morning and at bed time, and things look great. Your numbers are always where you want them. But what if you spent all day high? Well, then our A1C score would come back higher than expected, and we could investigate why the A1C and the meter don’t agree, and could then adjust your therapy.
The A1C score is not perfect, if you ran really high half the time and really low half the time, you could have a score that looked deceptively good. But it is still an important tool both to look at how good your diabetes control is, and if it is changing for the better or worse.
The test is usually run every three months for the simple reason that red blood cells live for three months, so any sample will reflect the sugar environment in your blood over the last three months.