• Serum creatinine, urea, sodium, potassium, calcium and bicarbonate
• Blood glucose
• Arterial blood gases and lactate if venous bicarbonate low or there is evidence of severe hypoperfusion or sepsis
• Full blood count
• Coagulation screen, blood film, reticulocyte count and LDH if the patient has purpura or jaundice, or low platelet count
• Blood culture if sepsis possible or cannot be excluded
• Urine stick test for glucose, blood and protein
• Urine protein to creatinine ratio if proteinuria detected by stick test
• Urine microscopy and culture
• ECG
• Chest X-ray
• Ultrasound of the kidneys and urinary tract if the cause of AKI is not known or obstruction of the urinary tract suspected

For later analysis

• Full biochemical profile, including urate
• Creatine kinase if suspected rhabdomyolysis (urine stick test positive for blood, but no red blood cells on microscopy; see Appendix 25.1)
• Erythrocyte sedimentation rate and C-reactive protein
• Serum and urine protein electrophoresis
• Serum complement and other immunological tests (antinuclear antibodies, antineutrophil cytoplasmic antibodies, antiglomerular basement membrane antibodies) if suspected acute glomerulonephritis/vasculitis
• Ultrasound of kidneys and urinary tract if not already done
• Echocardiography if clinical cardiac abnormality, major ECG abnormality, or suspected endocarditis
• Serology for HIV and hepatitis B and C if clinically indicated or dialysis is needed