Diabetes diagnosis is confirmed based on your symptoms as well as some laboratory tests. Type 2 diabetes is common and there are several diagnostic tests available to confirm its presence. However, diabetes often goes undiagnosed at an early stage and therefore almost 25% people are diagnosed with diabetes while they have already developed some complications. This means detection of high blood sugar at an early stage using right diagnosis, can result in appropriate treatment initiation as well as reduction in cardiovascular complications.
Types of diagnostic tests
Current preferred tests for diagnosis of diabetes are classified into two groups: serum glucose-based tests and glycated proteins. Serum glucose-based tests include fasting plasma glucose (FPG), random plasma glucose (RPG), and the oral glucose tolerance test (OGTT). The most well-studied and useful test for diabetes diagnosis is glycated haemoglobin test (HbA1C).
There is no diagnostic test that represents the “gold standard” for diabetes diagnosis. ADA recommendations focus on the FPG, whereas the World Health Organization (WHO) focuses on the OGTT. However, most practicing physicians also recommend other measures in such urinary glucose, RPG, and HbA1C in addition to the recommended tests. One survey revealed that 80% physicians use HbA1C, and 64% used FPG to confirm the diagnosis of diabetes.
1. Fasting Plasma
Diabetes diagnosis is confirmed based on specific laboratory tests at a clinic setting. If you present with some early symptoms of diabetes, your doctor may ask you to do one or more of the following tests,
|Result||Fasting Plasma Glucose (FPG)|
|Normal||less than 100 mg/dl|
|100 mg/dl to 125 mg/dl|
|Diabetes||126 mg/dl or higher|
2. Oral Glucose Tolerance Test (OGTT)
The oral glucose tolerance test (OGTT) determines your body’s response to sugar (glucose). During the test, first your fasting blood sugar levels are measured after which you need to consume a glucose solution containing 75 grams of sugar. Two hours after you have had the glucose solution, the blood sample is taken again to measure your blood glucose levels. This test helps to determine how well your body can handle glucose that is ingested through meals.
|Result||Oral Glucose Tolerance Test (OGTT)|
|Normal||less than 140 mg/dl|
|140 mg/dl to 199 mg/dl|
|Diabetes||200 mg/dl or higher|
3. Random Plasma Glucose Test
This test refers to blood sugar check that is done at any time of the day. The test that is performed at home using a glucometer (self-monitoring of blood glucose) is a random glucose test. Reading above 200 mg/dl indicated you have diabetes.
Also known as glycated haemoglobin test, HbA1c gives average blood glucose levels over past 2 to 3 months. This test basically determines the percentage of red blood cells, more precisely the haemoglobin that is coated with glucose. You need no do any fasting before going for this test. The frequency at which this test is decided by your doctor. Ideally Your HbA1c should be tested every 3 to 6 months. However, it might be done more often if your blood glucose levels are changing quickly.
The HbA1c reading reveals following results,
|Normal||less than 5.7%|
|5.7% to 6.4%|
|Diabetes||6.5% or higher|
- Cox ME, Edelman D. Tests for Screening and Diagnosis of Type 2 Diabetes Clinical Diabetes 2009 Oct; 27(4): 132-138.
- Diabetes Tests & Diagnosis. https://www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosis
- Diagnosing Diabetes and Learning About Prediabetes. http://www.diabetes.org/diabetes-basics/diagnosis/
- Diabetes Mellitus: An Overview: Diagnosis and Tests. https://my.clevelandclinic.org/health/diseases/7104-diabetes-mellitus-an-overview/diagnosis-and-tests