Your primary care provider or an endocrinologist (specialist of the endocrine system, which includes the pancreas) can run a variety of tests to determine if someone has diabetes. 

Diagnostic tests include: 

  • Fasting plasma glucose (FPG) test
  • Glycated hemoglobin (A1C) test
  • Random plasma glucose (RPG) test
  • Oral glucose tolerance test


Fasting Plasma Glucose (FPG) Test 

This test involves a blood test after fasting overnight for at least eight hours. It tests a person’s blood sugar level at a specific time, with a measure of 126 mg/dL or higher indicating diabetes. 

Glycated Hemoglobin (A1C) Test 

Instead of only looking at blood sugar levels from a specific moment, this blood test determines a person’s average levels from the past few months. A result of:

  • lower than 5.7 is normal,
  • 5.7 to 6.4 indicates prediabetes, and
  • 6.5 or higher is a diabetes indicator.   

Random Plasma Glucose (RPG) Test 

Similar to the FPG test, this blood test checks blood sugar levels at a specific moment. The difference is, it can be at any time, with fasting not required. In this case, if a person has other symptoms and has a level of 200 mg/dL or higher, it suggests diabetes.

Oral Glucose Tolerance Test 

This test is for pregnant women believed to have a specific form of this condition, known as gestational diabetes (aka, diabetes during pregnancy). It involves fasting overnight and then drinking a sugary liquid in the doctor’s office the next morning. Blood sugar levels are monitored over the next two hours.

  • Under 140 mg/dL is a healthy reading.
  • Between 140 and 199 mg/dL indicates prediabetes.
  • Over 200 mg/dL after two hours has passed indicates diabetes

Disclaimer: this article does not constitute or replace medical advice. If you have an emergency or a serious medical question, please contact a medical professional or call 911 immediately. To see our full medical disclaimer, visit our Terms of Use page.

More about Diabetes

Written by

Fact Checked by