Haemolysis is one of the most common causes of samples rejection in laboratory diagnosis. It does not only prolongs the waiting period for the administration of appropriate therapy and medical care but this laboratory mistake has multiple negative effects on all the health care participants, from the patient as a an object of medical care, to the health care employees and the institution itself. The consequences of haemolysis can vary from those of low impact, which are remediable through a repeated sampling and blood analysis, to those heavier and more serious, which can impact in a severe manner the patient's health, and eventually can cause professional liability and guilt. Haemolysis is mainly caused by mistakes in a pre-analytical phase, which can be avoided by following existing guidelines, standards, prescribed sampling techniques, storage and transport of samples. Continuous education and experience contribute to diminish the laboratories' mistakes created by nursing intervention. Every deviation of values from the foreseen intervals and general condition of the patient shall be obligatorily checked and analysed again. One of the most important measures of prevention against the output of unacceptable results is team work and interdisciplinary collaboration of the entire healthcare staff involved in the healthcare procedure, as well as mutual consulting in case of ambiguities and deviations. Not only are errors during pre-analytical phase, but also errors in analytical and post-analytical phase, of the utmost importance too. Those errors can be result of human factor, irregularly handling of laboratory's equipment, or computing errors in the analysis. Being acquainted with the critical phases of the complete output process of laboratory’s test results, enable us to act preventively with more attention, in order to avoid and timely recognize the same mistakes and obtain the final results accurate, above all. Prevention of laboratory mistakes requires good recognition and timely removal of possible samples. The cooperation starts with the nurse who takes the blood sample, followed by the laboratory technicians who prepare it for the analysis and by medical biochemists who confirm the accuracy of the results. A big role in this process is played by both continuous and comprehensible communication as well as by education of all the participants in the process of release of laboratory test results.