Physiological derangements such as hypoxemia and hyperkalemia are medical emergencies that warrant prompt interventions to prevent further patient clinical deterioration. However, in patients with myeloproliferative diseases or malignancies that result in extreme leukocytosis, hypoxemia and hyperkalemia demonstrated in laboratory results could be deceiving due to in vitro reactions and may not reflect actual patient condition. Clinicians have to be familiar with these phenomena so as to not cause harm by treating these spurious laboratory values.