What should you know about flank pain worse at night?

Pain at the side of the back may be muscular and change with movement or position. Kidney infection or a stone can cause flank pain with urinary changes, fever, nausea, or waves of severe discomfort. Pain that is deep, persistent, or not eased by rest can also involve a rib, spine, or other bone. Persistent bone pain is a presentation of several conditions, including [Stress Fracture](/conditions/stress-fracture/), vitamin D deficiency, and some cancers; the pain itself does not show which cause is present. A clinician may ask about injury, fever, urine, bowel symptoms, weight change, and previous cancer.

Record when the pain begins, its exact location, severity, triggers, and whether it wakes you. Note fever, urinary symptoms, numbness, weakness, or a rash. Avoid activities that clearly worsen it, but gentle movement may help a positional strain. Arrange a clinical assessment when pain persists, recurs, or interferes with sleep. Depending on the findings, care may include urine tests, blood tests, or imaging. Do not start supplements or strong pain medicines without checking interactions and kidney safety.

Seek urgent help for flank pain with fever and chills, vomiting, blood in the urine, inability to pass urine, severe sudden pain, fainting, or a very unwell feeling. Emergency assessment is also needed for new leg weakness, numbness around the groin, or loss of bladder or bowel control. If cancer has affected the bones, sudden severe pain after a minor movement may signal a fracture and needs prompt review.

Ask which features point toward muscle, kidney, nerve, or bone pain and whether you need tests. If a cancer-related cause is found, ask about [Cancer Pain](/conditions/cancer-pain/), [Bone-Strengthening Therapy](/treatments/supportive-and-palliative-care/bone-strengthening-therapy/), or [Palliative Radiotherapy](/treatments/radiation-oncology/palliative-radiotherapy/).