Medical laboratories have significant role in diagnosis, management and follow up of the patients. Occasionally, some results are “critical”, meaning that urgent/emergent  intervention is required in order to prevent major morbidities or mortality. During the last 40 years, significant attention has been paid to these results by laboratory specialists or clinicians. Rapid communication and reporting of critical results to management team has been emphasized and been considered as a requirement by some regulators. While rapid reporting of critical values has been accepted universally, the details of confirmation and rout of reporting has not been standardized. Herein, we present a brief review of various aspects of critical value results, such as how to diagnose, confirm and report them and describe theses process in our country and  through the world in order to reach a rather harmonized protocol capable of being established based on regional conditions.