Causes of left loin pain

The loin is the area between the lower ribs and the pelvis at the side of the back. Kidney stones often cause severe pain that comes in waves and may travel toward the groin; nausea or blood in the urine can occur. A kidney infection may cause steadier flank pain with fever, chills, feeling unwell, or painful and frequent urination. A urinary tract infection can cause burning, urgency, and lower abdominal discomfort, and may spread upward. Pain that changes with movement, lifting, twisting, or pressing the area can come from muscles or the back. These patterns overlap, so location alone cannot identify the cause.

Rest from movements that worsen the pain, drink normally unless a clinician has restricted your fluids, and note urinary changes, temperature, vomiting, and whether the pain travels. Do not use leftover antibiotics. A clinician may test urine, examine your abdomen and back, and decide whether imaging or treatment is needed. If you are pregnant, have one kidney, or have a weakened immune system, seek advice sooner.

Get urgent medical help for severe or rapidly worsening pain, fever with loin pain, repeated vomiting, confusion, faintness, inability to pass urine, or visible blood in the urine. Seek immediate care if pain follows a significant injury or occurs with marked weakness. A blocked or infected urinary system can require prompt treatment.

Tell the clinician when the pain began, whether it is constant or wave-like, and about fever, urine changes, bowel symptoms, periods, pregnancy possibility, and recent exertion. Ask whether you need urine testing, imaging, or pain relief advice.