Background: Severe pneumonia (SP) is a clinically critical acute disease which has a higher mortality rate among infectious diseases. In this report, a rare case of severe pneumonia with severely high lactic acid (up to 24 mmol/L) and relatively normal pH was analyzed. Methods: The case was discussed from different angles including acid-base balance disorder, the use of extractor-poreal membrane oxygenation (ECMO), dialysis treatment, circulatory disturbance, and inspection methodology. Results: Hypoxia and dissolution of muscles caused by circulatory disorders may be the cause of the abnormal in-crease of lactate in this case; while the relatively normal pH may be caused by the dialysis treatment. Conclusions: Such a high blood gas lactic acid value is extremely rare, and this increase is not due to the limita-tions of the test method. High lactic acid may not result in the significant decrease of pH when the patient receives continuous systemic treatment. © 2021 Verlag Klinisches Labor GmbH. All rights reserved.