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Lab Tests for Pre-Diabetes and Diabetes

Updated: Oct 28, 2023

Diabetes is a chronic condition that affects millions of people in India. According to the International Diabetes Federation (IDF), India has the second-highest number of people with diabetes in the world, with an estimated 77 million adults living with the disease in 2019. Pre-diabetes is also a common condition in India, where an estimated 77.2 million adults had impaired glucose tolerance in 2019. Early detection of pre-diabetes and diabetes is crucial for managing the disease and preventing complications. In this article, we'll discuss some of the lab tests that can help diagnose pre-diabetes and diabetes in the Indian context.

Fasting Plasma Glucose (FPG) Test

The FPG test is a simple blood test that measures your blood glucose level after an overnight fast. The test is usually performed in the morning after you've fasted for at least 8 hours. A normal FPG level is below 100 mg/dL. A level between 100 to 125 mg/dL may indicate pre-diabetes, while a level of 126 mg/dL or higher on two separate occasions is considered diagnostic for diabetes.

Oral Glucose Tolerance Test (OGTT)

The OGTT is another blood test used to diagnose pre-diabetes and diabetes. The test involves drinking a glucose solution, followed by blood tests at timed intervals to measure your blood glucose levels. The OGTT is more sensitive than the FPG test and can detect abnormalities in glucose metabolism before fasting glucose levels become elevated. In India, an OGTT is usually performed for pregnant women as a screening test for gestational diabetes. A 2-hour plasma glucose level between 140 to 199 mg/dL on two separate occasions is considered diagnostic for pre-diabetes, while a level of 200 mg/dL or higher on two separate occasions is considered diagnostic for diabetes.

Hemoglobin A1c (HbA1c) Test

The HbA1c test measures your average blood glucose level over the past two to three months. The test is a useful tool for monitoring diabetes control, but it may not be as accurate for diagnosing pre-diabetes and diabetes as the FPG and OGTT tests. In India, an HbA1c level of 5.7% to 6.4% is considered diagnostic for pre-diabetes, while a level of 6.5% or higher is considered diagnostic for diabetes.

Insulin and C-Peptide Tests

Insulin is a hormone produced by the pancreas that helps regulate blood glucose levels. C-peptide is a byproduct of insulin production. Measuring insulin and C-peptide levels can provide information about insulin resistance and insulin secretion, which are both important factors in the development of pre-diabetes and diabetes.

The Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) is a blood test that calculates insulin resistance based on fasting glucose and insulin levels. In India, HOMA-IR is increasingly being used as a tool for diagnosing pre-diabetes and diabetes. A HOMA-IR value of 1.0 or lower is considered normal, while a value between 1.0 to 1.9 is considered indicative of insulin resistance and pre-diabetes, and a value of 2.0 or higher is considered diagnostic for diabetes.

The insulin and C-peptide tests may also be used to distinguish between type 1 and type 2 diabetes. In type 1 diabetes, the pancreas produces little or no insulin, while in type 2 diabetes, the pancreas produces insulin, but the body is resistant to its effects. Insulin and C-peptide levels are usually lower in type 1 diabetes and higher in type 2 diabetes.


In India, diabetes is a major public health concern, with high rates of pre-diabetes and diabetes affecting millions of people. Early detection and management of pre-diabetes and diabetes is crucial for preventing complications and improving outcomes. Lab tests such as the FPG test, OGTT, HbA1c test, insulin and C-peptide tests, and HOMA-IR can help diagnose pre-diabetes and diabetes and provide valuable information for managing the disease. If you are at risk for pre-diabetes or diabetes, talk to your healthcare provider about which tests are appropriate for you and how often you should be tested. Remember, early detection and management can make all the difference in preventing complications and improving your quality of life.


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