A 24-year-old woman with asthma presented with symptoms of upper airway infection and tachypnoea and wheezes. She had a history of admissions to intensive care units (ICU) due to respiratory insufficiency. The initial lactate concentration was 2.1 mmol/l. The treatment consisted of inhaled and intravenous β ² agonists. Hereafter, the lactate concentration rose to 9.8 mmol/l, and the patient was admitted to the ICU due to severe asthma exacerbation. The elevation of lactate concentration cleared after discontinuation of β ² agonist therapy. Although lactic acidosis is a rare side effect to β ² agonist treatment, it is important to recog-nize it when present.