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Screening Guide
Diabetes Screening
Diabetes screening uses HbA1c or fasting glucose to find raised blood sugar early, when lifestyle changes and treatment work best.
Overview
Type 2 diabetes often creeps up quietly. Many people feel completely well while their blood sugar has been high for years.
The World Health Organization (WHO) estimates that about 14% of adults worldwide had diabetes in 2022, double the figure in 1990. Over time, high blood sugar can damage the eyes, kidneys, nerves, heart and blood vessels.
The good news is that a simple blood test can find it early. Catching raised blood sugar at the prediabetes stage gives you a real chance to slow it down or stop it progressing.
Who may want to understand this screening
WHO primary care guidance suggests testing adults aged 40 and above who are overweight (BMI above 25), and people with risk factors such as physical inactivity or a family history of diabetes.
The US Preventive Services Task Force (USPSTF) recommends screening adults aged 35 to 70 who are overweight or obese. It notes that a lower BMI cut-off of 23 may be more suitable for people of Asian background, which matters for many of us in Malaysia. If your result is normal, repeating the test about every 3 years is a reasonable approach.
You may need earlier or more frequent checks if you have had diabetes in pregnancy, have high blood pressure or high cholesterol, or already have prediabetes. Your doctor will guide you.
If you have symptoms, please don't wait for screening. See a doctor soon if you are very thirsty, passing urine often, losing weight without trying, or have blurred vision or wounds that heal slowly.
What screening may involve
Screening is a blood test. The two most common are HbA1c, which reflects your average blood sugar over the past two to three months, and fasting blood glucose, which measures your sugar level after not eating.
On the day, a nurse takes a small blood sample from your arm. It only takes a few minutes. Your doctor may also check your weight, BMI and blood pressure, as these are closely linked to diabetes risk.
Sometimes an oral glucose tolerance test is used instead. You have a fasting blood test, drink a sugary solution, then have another test two hours later.
What screening can — and cannot — tell you
WHO uses an HbA1c of 6.5% or higher, or a fasting plasma glucose of 7.0 mmol/L or higher, to diagnose diabetes. If you have no symptoms, the test is usually repeated on another day to confirm the result before a diagnosis is made.
An HbA1c between 5.7% and 6.4% is often called prediabetes. It means your risk is higher, and it's a good time to act on weight, activity and diet.
A normal HbA1c does not completely rule out diabetes. WHO notes that a value below 6.5% does not exclude diabetes found on glucose tests. HbA1c can also be less reliable in some anaemias and in inherited haemoglobin conditions such as thalassaemia, so your doctor may use glucose tests instead.
Screening does not diagnose you on its own. Your doctor will explain your results and plan any repeat tests or follow-up.
Practical considerations
If you are having a fasting glucose test, you'll need to avoid food and sugary drinks beforehand, usually overnight. Plain water is fine. An HbA1c test on its own does not need fasting, but check with the clinic in case other tests are planned.
Bring a list of your medicines and any previous sugar test results. Let the doctor know if you have anaemia, thalassaemia or are pregnant.
If your results are raised, your doctor will talk you through the next steps. This may include repeat testing, lifestyle advice and checks of your kidneys, eyes and feet.
Sources
1. Diabetes (fact sheet) — World Health Organization, 2024
2. Use of Glycated Haemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus: Abbreviated Report of a WHO Consultation — World Health Organization, 2011
3. Training Manual: WHO Package of Essential NCD Interventions (PEN) – Management of Type 2 Diabetes — World Health Organization, n.d.
4. Prediabetes and Type 2 Diabetes: Screening (Final Recommendation Statement) — US Preventive Services Task Force, 2021
Common questions
Do I need to fast for diabetes screening?
It depends on the test. A fasting glucose test needs you to avoid food beforehand, usually overnight, while HbA1c alone does not.
What HbA1c level means diabetes?
WHO uses an HbA1c of 6.5% or higher to diagnose diabetes. Levels from 5.7% to 6.4% are often called prediabetes and mean your risk is higher.
How often should I be screened?
If your result is normal, the USPSTF suggests about every 3 years is reasonable. You may need more frequent checks if you have prediabetes or other risk factors.
I feel fine. Could I still have diabetes?
Yes. Type 2 diabetes often causes no symptoms for years, which is why a blood test is useful.
Can prediabetes be reversed?
Often, yes. Losing some weight, being active and eating well can bring blood sugar back towards normal or delay diabetes.