Increase in lactate levels (hyperlactataemia) is common in critically ill patients and it is a sensitive marker in early identification of patients who are critically ill. Blood lactate is also a predictor of clinical outcomes. High level of lactate is associated with high mortality as well as increased morbidity. Capillary blood sample is easy to collect, less painful, and its measurement using handheld device which may allow more rapid determination of test results in ED. This rapid lactate measurement could aid early recognition of patients at high risk of mortality and morbidity. However, the accuracy of this rapid capillary lactate measurement using handheld devices has not been well studied in ED patients.