Diabetes Screening: A1c, Fasting Blood Glucose, and OGTT#

Prediabetes means your blood sugar is higher than normal but not yet in the diabetic range. It is a strong signal to act now: lifestyle changes can prevent or significantly delay progression to type 2 diabetes. Roughly 5 to 10% of people with prediabetes progress to diabetes each year without intervention. With sustained lifestyle change (weight loss of 5 to 7%, 150 minutes of moderate exercise per week, and a Mediterranean-style or DASH eating pattern), many people return to normal numbers.

A single result above 7.0 mmol/L meets the threshold for diabetes, but Canadian guidelines recommend a second confirmatory test on a different day before making the diagnosis - unless you also have clear symptoms (excessive thirst, frequent urination, unexplained weight loss). The repeat can be a fasting glucose, an A1c, or an OGTT. A TeleTest clinician will arrange the confirmatory test and explain next steps once both results are in.

Yes. A1c reflects how long red blood cells are exposed to sugar in the bloodstream. Anything that makes red blood cells live longer than normal can falsely raise A1c. Common causes:

• Iron-deficiency anemia (untreated)
• B12 or folate deficiency anemia
• Recent loss of a spleen (asplenia)

In these situations, a fasting glucose or OGTT is a better test.

Yes. Anything that shortens the lifespan of red blood cells lowers A1c independent of your actual blood sugar. Common causes:

• Thalassemia and other hemoglobinopathies
• Sickle cell trait or disease
• Hemolytic anemia
• Recent blood transfusion
• Pregnancy (red blood cells turn over faster)
• Recent treatment for iron, B12, or folate deficiency
• Some kidney and liver diseases
• Erythropoietin treatment

If your A1c does not match your symptoms or your fasting glucose, ask your clinician about using a different test.

Yes, modest ones. People of African, South Asian, and East Asian backgrounds tend to have slightly higher A1c values for the same average blood sugar compared to white populations. Diabetes Canada uses the same diagnostic cutoffs regardless of ethnicity, but clinicians keep this in mind when results are borderline.

A fasting glucose itself measures the sugar in your blood at that moment - there is no biological "false positive" the way A1c can be skewed by red cell lifespan. However, a single fasting glucose can be misleading in two situations:

• Recent illness, surgery, or major stress: blood sugar can run higher for days to weeks.
• Inadequate fasting: even a small amount of food, juice, coffee with milk, or sugary medication within 8 hours can raise the result.

Repeat testing on another day - properly fasted, when you are well - is how clinicians sort this out.

This happens. The two tests measure different things, and a mismatch is not unusual. A clinician usually relies on:

• The higher of the two if both are abnormal
• Symptoms (excessive thirst, weight loss) tip toward diabetes
• Repeat testing or an OGTT to settle borderline cases

Canadian Choosing Wisely guidance does not recommend repeated finger-prick testing for people who are not on insulin and do not have recurrent low blood sugar episodes. For most people with prediabetes or type 2 diabetes managed without insulin, A1c every 3 to 6 months is sufficient to track control. If you are concerned about low blood sugar symptoms, please see a clinician in person at a walk-in or urgent care centre.

A CGM is a small sensor worn on the arm or abdomen that measures glucose in the fluid under your skin every few minutes. It is most useful for people on insulin or with frequent low blood sugar episodes. For people with prediabetes or type 2 diabetes managed with pills and lifestyle, a CGM is not routinely recommended, although some patients use one for short periods to learn how meals and exercise affect their numbers.

TeleTest can issue a prescription for a CGM if you have a confirmed diabetes diagnosis. CGMs are also available for purchase over the counter at most pharmacies without a prescription, but private insurance plans usually require a prescription for reimbursement and most plans only reimburse for type 1 diabetes or insulin-treated type 2.

Yes. Pregnancy uses a separate set of guidelines (gestational diabetes screening) and different thresholds. Most pregnant patients are screened between 24 and 28 weeks with a 50g oral glucose challenge test, followed by a 75g OGTT if the screen is abnormal. TeleTest does not currently manage prenatal care; if you are pregnant, please see your prenatal-care provider or family doctor for gestational-diabetes screening.

TeleTest can order monitoring labs (A1c, kidney function, cholesterol) for patients with type 1 diabetes who have an established care plan. We can issue prescriptions for insulin only when type 1 diabetes is documented and we have access to your most recent specialist or family-doctor records. For ongoing dose adjustment and complex management, type 1 diabetes is best handled by an endocrinology team or family doctor with a diabetes focus.

For type 2 diabetes, TeleTest can:

• Order A1c, lipids, kidney function, and other monitoring labs
• Issue prescriptions for first- and second-line oral diabetes medications when clinically appropriate
• Issue prescriptions for newer injectable diabetes and weight-management medications when criteria are met
• If your management becomes complex, you would arrange ongoing care with your family doctor or seek a local in-person endocrinologist

Yes, A1c responds within 6 to 12 weeks to genuine changes in average blood sugar. A drop of 0.5 to 1.0% after starting a new medication or significant weight loss is common and reflects real improvement. Repeat A1c every 3 months until you are stable, then every 6 to 12 months.

Often yes, particularly with prediabetes or recently diagnosed diabetes. Studies show that sustained weight loss of 5 to 10% combined with regular physical activity can return A1c to normal in a substantial proportion of people. The DiRECT trial in the UK showed that about 46% of people with early type 2 diabetes achieved remission (A1c below 6.5% without medication) at one year with structured weight loss.

Prediabetes and diabetes rarely travel alone. They cluster with high blood pressure, high cholesterol (especially elevated triglycerides and low HDL), and abdominal weight gain - together called metabolic syndrome. If your A1c or fasting glucose is abnormal, your clinician will usually recommend checking your blood pressure, a lipid panel, and a kidney-function test (creatinine plus a urine albumin/creatinine ratio) to get the full cardiovascular picture.

Diabetes Canada recommends:

• If you have classic symptoms (thirst, frequent urination, unexplained weight loss) plus a single test in the diabetic range, the diagnosis is confirmed.
• Without symptoms, a second confirmatory test on a different day is required. The second test can be the same test or a different one.

A TeleTest clinician will arrange the confirmatory test once we see the first result.