Blood tests to diagnose diabetes are fasting plasma glucose (FPG), oral glucose tolerance test (OGTT), random plasma glucose test.
Blood tests are done to diagnose diabetes. The following tests are done for diagnosis:
- Fasting plasma glucose (FPG)
- Oral glucose tolerance test (OGTT)
- Random plasma glucose test
Fasting plasma glucose (FPG): This test measures blood glucose level in the morning (after 8 hours of fasting) before you eat or drink anything even tea or coffee. The test can help to diagnose diabetes and pre-diabetes.
Diagnosis based on fasting plasma glucose
- FPG <99 mg/dl is considered normal
- FPG between 100 to 125 mg/dl indicates pre-diabetes (or impaired fasting glucose)
- FPG >126 mg/dl indicates diabetes
Oral glucose tolerance test (OGTT): In this test the blood glucose level is measured in a person after drinking 75 grams of glucose solution. The test is done after at least 8 to 12 hours of fasting. The test can help to diagnose diabetes and pre-diabetes. OGTT is more sensitive as compared to FPG test for diagnosis of pre-diabetes, but it is more cumbersome as compared to FPG.
Based on the results of glucose tolerance test the following diagnoses may be made:
- Normal response: In people with normal glucose tolerance test the 2-hour glucose level remains lower than 140 mg/dl, and all values between 0 and 2 hours remain lower than 200 mg/dl.
- Impaired glucose tolerance: If your fasting plasma glucose is less than 126 mg/dl and the 2-hour glucose level is between 140 and 199 mg/dl you have impaired glucose tolerance test
- Diabetes: If your fasting plasma glucose is greater than 126 mg/dl and/or the 2-hour glucose level is greater than mg/dl repeatedly (done on different days)---you have diabetes.
- Gestational diabetes: A woman is diagnosed with gestational diabetes if she has any two of the following after 100g OGTT---fasting plasma glucose > 95 mg/dl, 1-hour glucose > 180 mg/dl, 2-hour glucose level > 155 mg/dl, or a 3-hour glucose level > 140 mg/dl.
Random plasma glucose test: The test measures blood glucose at any time of the day disregarding to when the person last ate. This test is usually done to diagnose diabetes but not pre-diabetes.
- Random blood glucose level > 200 mg/dL along with symptoms of diabetes (such as increased urination, increased thirst, unexplained weight loss) indicates that you may have diabetes.
- Your doctor may recommend FPG or OGTT to confirm the diagnosis.
If your blood sugar or blood glucose levels are elevated your doctor will recommend repeat testing on a different day to confirm the results.
Dr Poonam Sachdeva, our in-house medical expert talks about the why what and how in diabetes.
Read more articles on Diabetes Diagnosis
All possible measures have been taken to ensure accuracy, reliability, timeliness and authenticity of the information; however Onlymyhealth.com does not take any liability for the same. Using any information provided by the website is solely at the viewers’ discretion. In case of any medical exigencies/ persistent health issues, we advise you to seek a qualified medical practitioner before putting to use any advice/tips given by our team or any third party in form of answers/comments on the above mentioned website.