Which initial investigations should I perform in a patient with suspected bloodstream infection?

Initial investigations for a patient with suspected bloodstream infection should include taking blood cultures before starting antimicrobial treatment to identify the causative organism and guide therapy. A venous blood test panel should be performed, including blood gas analysis (with glucose and lactate measurement), full blood count, C-reactive protein, urea and electrolytes, creatinine, liver function tests, and a clotting screen. These tests help assess the severity of infection, organ function, and systemic response. Additionally, investigations to find the source of infection should be tailored to the clinical history and examination findings, including urine analysis and chest X-ray as routine initial tests. If no source is identified, imaging of the abdomen and pelvis may be considered. Early involvement of surgical or interventional radiology teams is recommended if a source requiring intervention is suspected. In children under 3 months with suspected sepsis, lumbar puncture should be performed unless contraindicated. These investigations should be done promptly, ideally before antibiotic administration, to optimize diagnosis and management NICE NG51.