Rationale: Ozone autohemotherapy as an alternative treatment method has been applied to the treatment of several diseases. Here, we report a patient used ozone autohemotherapy to treat her hypertension and diabetes. Nevertheless, the patient occurred sudden dizziness and black haze due to hyperkalemia. Patient concerns: A 54-year-old woman who was admitted to our emergency department complaining of sudden dizziness and black haze for 5 hours. Diagnoses: The blood potassium test showed hyperkalemia. Upon further inquiry of her medical history, the patient received ozone autohemotherapy to treat hypertension and diabetes for 9 days prior to admission. Interventions: The ozone therapy had been asked to stop. Insulin, sodium bicarbonate, and sodium polystyrene sulfonate were administered to the patient. Outcomes: After treatment, blood potassium remained in the normal range. After 3 days of treatment, the 24-hour dynamic electrocardiogram revealed sinus rhythm with an average heart rate of 82beats/min, occasional ventricular premature beats, occasional ventricular premature beats, and no ST segment depression. Lessons: Although ozone therapy is widely used in the treatment of several diseases, adverse reactions should be given attention in clinical practice, especially in patients with chronic kidney disease.