Introduction: In vitro hemolysis is the primary cause of sample/test rejection by the laboratory., Case Report: A 10-year-old, admitted with an asthma attack in the emergency-room, medicated with albuterol sulphate (intravenous bronchodilator that could induce hypokalemia), needed laboratory test monitoring. The physician prescribed the technical-nurse to perform blood sampling for: complete blood count, electrolytes, glucose, and blood gas analysis-within 30min after therapy. Samples were delivered to laboratory with a note "I had difficult to locate an appropriate access to perform the blood collection"., Laboratory Results: Glucose: 4.77 mmol/L. Complete blood count revealed discreet eosinophilia 0.13x10 9 /L, and thrombocytopenia 18x10 9 /L. However, platelet clumps were observed in peripheral blood smear. Blood gas analysis was unreported, laboratory informed that sample had micro clots.Electrolytes: laboratory did not report the results; sample hemolyzed. 0.9 g/L of free hemoglobin is the cut-off defined by the laboratory; the sample presented 2.3 g/L of free hemoglobin. 3.9 mmol/L of potassium was the unreported result vs 2.1 mmol/L in the new sample.Briefly, the laboratory technician was trained to hide potassium results on hemolyzed sample due to the potential overestimation. Even if the hemolyzed sample presented a potassium value close to the lower reference range value (3.5-5.1 mmol/L), reporting the potassium result could allow the physician starting proper therapy to revert the hypokalemia by albuterol sulfate., Conclusion: The laboratory should be aware of the clinical patient conditions and of the related physician needs, before hiding results. Therefore, both the laboratory and the clinic personnel should communicate in order to guarantee the patient safety., Competing Interests: *These graduation-students contributed equally to this work. Therefore, their names are listed in alphabetical order., (Copyright © 2020 International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). All rights reserved.)