The following tests are used to diagnose diabetes mellitus :- Fasting plasma glucose (FPG) :-This test is convenient, reliable and cost effective.In this test ,venous blood sample is drawn in a fasting state (after 8 hours of fasting)and the preferred time is morning after overnight fasting.The values of FPG are given below:- 1.Blood glucose level upto 99mg/dl is normal. 2.Blood glucose level form 100mg/dl-125mg/dl is prediabetes. 3.blood glucose level of 126mg/dl and onwards is diabetes. Oral glucose tolerance test (OGTT):- OGTT is more sensitive as compared to FPG,however the test is less convenient.In this test the patient is asked to drink 75gms of glucose mixed with water in a fasting state (after 8 hours of fasting).The blood sample is drawn just before and 2 hours after the patient drinks 75gms of glucose.The values of the test are given below:- Blood glucose levels after 2 hours 1.Blood glucose level upto 139mg/dl is normal. 2.Blood glucose level from 140mg/dl -199md/dl is prediabetes. 3.Blood glucose level of 200mg/dl and onwards is diabetes Oral glucose tolerance for diagnosing gestational diabetes :- This test is advisable to all the pregnant women in 24th-28th weeks of pregnancy.In this test the patient is asked to drink 50mg of glucose mixed with water at anytime(not necessarily in fasting state).The blood sugar levels are measured just before and 2 hours after drnking glucose and if the the blood glucose level after 2 hours is more than 140mg/dl ,then the test is repeated with 75gms. of glucose.The values of the test are given below:- 1.Fasting- 105mg/dl 2.After 1hour- 190mg/dl 3.After 2 hours- 165mg/dl 4.After 3 hours- 145mg/dl If any two out of the four readings given above are met or exceeded,a dignosis of GDM is established.