Some commonly performed laboratory tests include pregnancy tests, renal function tests-24 hours urine and clearance test, BUN, serum creatinine, serum electrolytes, acid base imbalance, liver function test, oral glucose tolerance test (OGTT), glycosylated hemoglobin (HbA1C) and pancreatic function test amylase, lipase, ERCP and microlabumin test. These tests, their indication, procedure, normal reference range, high and low values are described. Some special tests like HbA1C, microalbumin are very important to assess early complications in diabetes and hypertension. Oral glucose tolerance test is very important for differentiating normal person, impaired glucose tolerance (IGT) and a frank diabetes. So, patient preparation for this test and necessary advice before the test are very important which is mentioned in details. Serum electrolytes, e.g. Na+, K+, Cl- and HCO3-, their normal reference ranges, causes of metabolic acidosis and alkalosis, respiratory acidosis and alkalosis are also mentioned.