Diabetes Screening: Who Should Be Tested and Which Test Is Used

You feel fine, but your parent has diabetes, or your clinician mentioned your weight or blood pressure. You wonder if you should be tested, and which test is right. This guide explains who should be screened for type 2 diabetes and prediabetes, the tests clinicians use, and how Canadian and US advice compares.

Why screen for diabetes

Type 2 diabetes develops slowly. Many people have high blood sugar for years before they notice symptoms. During that time, it can start to damage blood vessels, nerves, eyes, and kidneys [2].

Prediabetes means blood sugar is higher than normal but not yet in the diabetes range. It raises the chance of developing diabetes and heart disease. Finding it gives you a chance to act early.

Common risk factors

• Age 40 or older.
• Overweight or obesity, especially extra weight around the waist.
• A parent, brother, or sister with type 2 diabetes.
• High blood pressure or high cholesterol.
• Diabetes during a past pregnancy, or a baby born weighing more than 4 kg (about 9 pounds).
• Polycystic ovary syndrome.
• Belonging to a population with higher rates of diabetes, including people of South Asian, East Asian, African, Hispanic, or Indigenous ancestry [1][2].

The screening tests

• A1C: shows average blood sugar over about 3 months. No fasting needed.
• Fasting plasma glucose (FPG): blood sugar after at least 8 hours without food.
• Oral glucose tolerance test (OGTT): blood sugar 2 hours after drinking a sweet drink with 75 g of glucose.

What your doctor looks at

The cut points

For diabetes, Canada and the US use the same cut points [2][4]:

• A1C: 6.5 percent or higher.
• Fasting glucose: 7.0 mmol/L (126 mg/dL) or higher.
• 2-hour OGTT: 11.1 mmol/L (200 mg/dL) or higher.

Without clear symptoms, a high result is confirmed with a second test.

For prediabetes, the cut points differ:

• The American Diabetes Association (ADA) uses A1C 5.7 to 6.4 percent and fasting glucose 5.6 to 6.9 mmol/L (100 to 125 mg/dL) [4].
• Diabetes Canada uses A1C 6.0 to 6.4 percent and fasting glucose 6.1 to 6.9 mmol/L [2].
• Both use a 2-hour OGTT of 7.8 to 11.0 mmol/L (140 to 199 mg/dL).

So more people are labelled with prediabetes under US criteria.

Who should be screened

US guidance

The US Preventive Services Task Force (USPSTF) 2021 recommendation [1]:

• Screen adults aged 35 to 70 who have overweight (BMI 25 or more) or obesity (BMI 30 or more).
• Consider screening earlier for people from groups with higher diabetes rates.
• Use a lower BMI cut point, 23 or more, for Asian Americans.
• Repeat about every 3 years if results are normal.
• Refer people with prediabetes to effective prevention programs.

The ADA recommends testing all adults from age 35, and earlier for adults with overweight plus other risk factors.

Canadian guidance

Diabetes Canada's guideline [2]:

• Test everyone aged 40 and older at least every 3 years with a fasting glucose or A1C.
• Test earlier or more often for people with risk factors or a high score on a risk calculator such as CANRISK.

The Canadian Task Force on Preventive Health Care 2012 guideline took a risk-first approach [3]:

• Use a validated risk calculator, such as FINDRISC or CANRISK, every 3 to 5 years.
• Do not routinely screen people at low to moderate risk.
• Screen people at high risk with A1C every 3 to 5 years, and people at very high risk every year.

The Task Force ended its mandate in March 2026, and its guideline remains posted for reference.

The key differences

• Start age: 35 in the US, 40 in Canada.
• Who: the USPSTF links screening to weight; Diabetes Canada tests all adults from 40; the Canadian Task Force used a risk calculator first.
• Prediabetes cut points are lower in the US.

What happens if you have prediabetes

Prediabetes does not always lead to diabetes. Action helps.

In the US Diabetes Prevention Program trial, adults with prediabetes who joined an intensive lifestyle program lowered their chance of developing diabetes by 58 percent over about 3 years. In absolute terms, about 1 case was prevented for every 7 people in the program [5]. The program aimed for about 7 percent weight loss and 150 minutes of activity each week.

Your clinician may suggest a lifestyle program, retesting each year, and checks of blood pressure and cholesterol. Ask your clinician or pharmacist before you start any medicine.

Questions to ask your clinician

• Based on my risk factors, should I be screened now?
• Which test do you suggest for me, and do I need to fast?
• If my result is borderline, which guideline cut point are you using?
• How often should I be retested?
• Is there a diabetes prevention program I can join?
• Should my blood pressure and cholesterol be checked too?

When to get care quickly

Go to the emergency department if you have strong thirst, passing a lot of urine, and weight loss with vomiting, stomach pain, or fast or deep breathing. Call 911 for confusion or severe drowsiness. These can be signs of dangerously high blood sugar.

Bottom line

Type 2 diabetes is often silent, so screening finds it early. The US screens adults 35 to 70 with overweight or obesity. Diabetes Canada tests everyone from 40 every 3 years, and earlier with risk factors. The diabetes cut points match, but the US labels prediabetes at lower numbers. Lifestyle programs can greatly lower the chance that prediabetes becomes diabetes.

Primary AI can show you the guideline and study sources behind this topic in plain language, so you can bring better questions to your appointment.