Diabetes: A1c and Fasting Blood Glucose
Commonly asked questions about diabetes screening and testing
Diabetes is a disease diagnosed when an individual has elevated blood sugars. Current Canadian Diabetes Guidelines use Fasting Blood Sugar (FBS) and Glycated Hemoglobin (a1c) to define the presence of diabetes and monitor diabetes control. The following ranges define when an individual has normal, at-risk, pre-diabetes or diabetes status:
Glycated Hemoglobin (a1c)
< 5.6 mmol/L
6.5% or higher
Canadian Diabetes Guidelines recommend screening every 3 years beginning at age 40, or earlier if you are at risk. TeleTest uses the CANRISK tool to estimate your risk based on your intake questionnaire, and determine the frequency of your desired screening and if you should be screened earlier. If you have an abnormal initial test result and qualify for more frequent insured screening, you can arrange follow-up testing at that defined interval determined by the Canadian Diabetes Association through TeleTest. Your TeleTest profile will let you order more frequent insured testing based on a risk assessment of your prior result. If you do not qualify for more frequent testing, you can pay a 3rd party lab fee to still access testing.
Yes, you can order fasting blood glucose or A1c tests as frequently as you want, but you will have to pay 3rd party lab testing fees through TeleTest to access testing. When you order the testing, if you don’t meet insured criteria - you will be prompted with an additional lab fee at checkout. Once we accept payment, simply head into the lab for testing and show them our requisition with the test information.
Glycated Hemoglobin (a1c) is the total amount of sugar attached to a red blood cell circulating in your bloodstream averaged over the typical life span of a red blood cell. The a1c correlates with the ‘average’ sugar level in your bloodstream over the most recent 8-12 weeks. It isn’t really affected by recent changes in blood sugar (i.e. whether you fast or don’t fast, the A1c is constant). This ability to track your average sugars is the best approach to managing your overall diabetic health.
Canadian Choosing Wisely guidelines DO NOT recommend repeat finger-prick glucose readings unless you are on insulin or are experiencing recurrent hypoglycemic episodes from multiple diabetic medications. The a1c level is used to guide medical therapy in diabetes, and screen for diabetes in non-diabetics. If you are concerned about experiencing hypoglycemic episodes, we suggest consulting an in-person health care provider at a local walk-in clinic or urgent care centre.
A TeleTest physician will notify you of your diagnosis, and recommend a medication and treatment plan for your diabetes. If you test positive for diabetes on an initial screen, guidelines recommend a repeat confirmatory test completed on another day (fasting blood glucose, a1c or a 2-hour plasma glucose test following a 75g glucose challenge). A 75g glucose test involves drinking a beverage (supplied by the lab) containing 75g of sugar and then checking your blood glucose levels after 2 hours. Current Canadian guidelines DO NOT recommend using the 75g glucose test as an initial screen for diabetes.
- False high A1c levels (you do not have diabetes, but the a1c is high) can occur in people with B12 or folate-deficient anemia where red blood cells live longer.
- False low a1c levels (patient has diabetes, but the a1c is normal) can occur in conditions where red blood cells are being turned over faster than normal - conditions like thalassemia, G6PD deficiency); individuals with anemia treated recently with iron/b12/folic acid.
- A fasting blood glucose cannot be a false positive or false-negative result.
If you would like a prescription for a continuous glucose monitor, we can provide a prescription for a Freestyle Libre device provided you have a diagnosis of diabetes requiring monitoring.