How Is Diabetes Diagnosed? Key Tests and Criteria
Main Diagnostic Tests for Diabetes
This test measures blood sugar after an overnight fast (at least 8 hours).
Prediabetes: 100–125 mg/dL
Diabetes: 126 mg/dL or above
This test reflects average blood glucose levels over the past 2–3 months.
Prediabetes: 5.7%–6.4%
Diabetes: 6.5% or above
The use of the A1C test has increased significantly, especially in countries like Australia, where screening rates more than doubled between 2015 and 2019.
This test measures blood glucose before and after drinking a glucose-rich beverage.
Prediabetes: 140–199 mg/dL
Diabetes: 200 mg/dL or above
OGTT use has declined in favor of A1C testing in many regions.
This test measures blood glucose at any time, regardless of when you last ate.
This test checks for sugar or ketones in the urine, which may indicate diabetes or complications related to it.
Test Accuracy
- A1C Test: Sensitivity ranges from 24%–78%, and specificity ranges from 79%–100% at the 6.5% threshold for diagnosing diabetes.
- Fasting Plasma Glucose (FPG): Sensitivity ranges from 40%–94%, and specificity ranges from 83%–100% at the 126 mg/dL threshold.
These tests are most reliable when used together or confirmed with repeat testing.
Global Diabetes Statistics
People living with diabetes in 2022 (up from 200 million in 1990)
Of adults worldwide had diabetes in 2022
Deaths linked to diabetes in 2021
Early diagnosis is critical to prevent complications like blindness, kidney failure, heart attacks, and strokes.
Diagnostic Thresholds
| Test | Normal | Prediabetes | Diabetes |
|---|---|---|---|
| A1C | < 5.7% | 5.7%–6.4% | ≥ 6.5% |
| Fasting Plasma Glucose | ≤ 99 mg/dL | 100–125 mg/dL | ≥ 126 mg/dL |
| OGTT (2 hours) | ≤ 139 mg/dL | 140–199 mg/dL | ≥ 200 mg/dL |
| Random Plasma Glucose | — | — | ≥ 200 mg/dL |
Key Facts
- Most diabetes diagnoses require at least two abnormal test results, unless symptoms are severe.
- The use of A1C as a diagnostic tool has increased, and in some countries, its screening rates now surpass those of the OGTT.
- Timely diagnosis reduces the risk of life-threatening complications related to diabetes.
Conclusion: Diabetes is diagnosed using several key blood sugar tests with well-established thresholds. The A1C, FPG, OGTT, and random plasma glucose tests are the most commonly used, each with specific cutoffs for normal, prediabetes, and diabetes. With the global increase in diabetes cases, early and accurate diagnosis has never been more important.
At NAMG, we are committed to offering high-quality care for diabetic patients. By utilizing RPM (Remote Patient Monitoring) services, we not only help patients manage their diabetes more effectively but also empower them to take control of their health in a convenient and less invasive way.
Whether you're managing Type 1 or Type 2 diabetes, our RPM services can help you:
- Maintain stable blood sugar levels
- Reduce the risk of complications
- Receive timely medical interventions
- Live a healthier, more balanced life
Contact NAMG Today!
If you're ready to start managing your diabetes more effectively with our RPM services, contact Northern Arizona Medical Group today!
Call us at 928-757-8440 or visit our website at namg.us to learn more about our RPM services and how we can help you take charge of your health.
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