Pseudohyperkalaemia is an in vitro phenomenon in which the potassium (K⁺) concentration is spuriously elevated in the presence of normal circulating plasma potassium concentrations. In practice, the distinction between pseudohyperkalaemia and true hyperkalaemia is challenging especially in acutely ill patient without marked cytosis. Furthermore, a persistent critical potassium level would further bolster the suspicion of true hyperkalaemia thus leading to inadvertent administration of potassium-lowering therapy. A 21-year-old gentleman presented with a chief complaint of haematuria for 1 day duration associated with bilateral colicky flank pain and was treated as complicated urinary tract infection. The presence of persistent critical serum potassium level had led to the pursuit of anti-hyperkalaemia therapy during hospitalisation. Nonetheless, the diagnosis of pseudohyperkalaemia was eventually established via multi-modal biochemical evaluations as well as a demonstration of red cell membrane instability in the presence of Southeast Asian Ovalocytosis. This report highlights the importance of maintaining a healthy skepticism about pseudohyperkalaemia in subjects with profoundly raised serum potassium level, who lack other supporting features. An integrated approach is warranted in such cases, particularly collaboration with chemical pathologist in discriminating true hyperkalaemia from pseudohyperkalaemia as well as to establish the proper method in measuring the potassium level of such patients in the future.

假性高钾血症是一种体外现象，其中钾 (K ⁺ ) 浓度在正常循环血浆钾浓度存在的情况下虚假升高。在实践中，假性高钾血症和真性高钾血症之间的区别具有挑战性，特别是对于没有明显细胞增多的急性患者。此外，持续的临界钾水平会进一步增加对真正高钾血症的怀疑，从而导致无意中进行降钾治疗。一名 21 岁男性，主诉为持续 1 天的血尿，并伴有双侧腹绞痛，并因复杂性尿路感染而接受治疗。持续存在临界血清钾水平导致住院期间寻求抗高钾血症治疗。尽管如此，假性高钾血症的诊断最终是通过多模式生化评估以及东南亚卵圆细胞增多症存在下红细胞膜不稳定的证明而确定的。本报告强调了对于血清钾水平显着升高但缺乏其他支持特征的受试者保持对假性高钾血症的健康怀疑的重要性。在这种情况下，需要采取综合方法，特别是与化学病理学家合作，区分真正的高钾血症和假性高钾血症，并建立未来测量此类患者钾水平的正确方法。