Back left flank pain: causes and next steps

Flank pain is located along the side of the back beneath the ribs and above the hip. Pain that follows exercise or worsens when the back moves or is pressed can fit a muscle problem. Kidney infection often presents with flank pain accompanied by fever, chills, nausea, or painful urination. Kidney stones may produce sudden, severe waves of pain, sometimes with nausea or blood in urine. Urinary tract infection may cause urgency, frequency, or burning, but flank pain with fever requires prompt attention.

Pause activities that strain the back and continue gentle movement as tolerated. A warm pack can be useful for muscular tightness. Note the pain’s duration, movement triggers, urine changes, temperature, and any nausea. Arrange an appointment if the pain lasts, recurs, or interferes with normal activity. A clinician can decide whether examination, urine testing, or imaging is appropriate.

Seek urgent care for sudden severe pain, fever, shaking chills, ongoing vomiting, faintness, confusion, difficulty passing urine, or blood in urine. Get prompt assessment after trauma, during pregnancy, or with known kidney problems. If pain is mild but unexplained and continues, contact a healthcare professional rather than repeatedly self-treating it.

Ask which features make a muscle cause more likely, whether you need a urine test, and how to manage pain safely with your health conditions. Share recent lifting or sport, injuries, fever, bowel or urinary symptoms, and any history of stones or infections.