A 60-year-old man presents to the emergency department with complaints of persistent fatigue, weakness, and shortness of breath over the past week. He has a medical history of type 2 diabetes mellitus and chronic kidney disease (stage 3). His family reports that he has been increasingly lethargic and has had episodes of nausea and vomiting.

On examination, the patient appears ill and is tachypnoeic, with a respiratory rate of 24 breaths per minute. His blood pressure is 110/70 mmHg, and he has a heart rate of 100 beats per minute. Laboratory tests show a serum bicarbonate level of 18 mEq/L, a low arterial blood pH of 7.32, and an elevated serum creatinine level of 3.0 mg/dL. Urinalysis reveals a specific gravity of 1.010 and the presence of ketones.

Given his clinical presentation and lab results, the patient is diagnosed with metabolic acidosis, likely due to his chronic kidney disease and possible diabetic ketoacidosis (DKA) secondary to poorly controlled diabetes. He is started on intravenous fluids and bicarbonate therapy to correct the acidosis. The patient's diabetes management is also reviewed, and he is referred to a diabetic educator for better glycemic control. Regular monitoring of his renal function and electrolyte levels is arranged, along with follow-up appointments to address his kidney disease and overall health.