Pain in both lumbar/flank areas after urination for 3 days can occur with a urinary tract infection, an infection involving the kidneys, or less commonly a urinary stone or a non-urinary back problem. It cannot be diagnosed safely from this symptom alone.

Because flank/back pain with urinary symptoms can signal a kidney infection, arrange an in-person medical assessment today, ideally with a urine dipstick/urinalysis and urine culture. A clinician may also check temperature, kidney function, and consider ultrasound or CT if a stone or obstruction is suspected.

Seek urgent/emergency care now if you have any of these:

Until reviewed: drink normal amounts of water if you can keep fluids down, rest, and use paracetamol/acetaminophen as directed on the label if safe for you. Avoid self-starting antibiotics, because the correct treatment depends on urine findings and local resistance patterns. The NHS kidney-infection guidance also treats back/side pain with urinary symptoms, fever, vomiting, blood in urine, or reduced urine output as reasons for urgent assessment.

Useful details to tell the clinician: burning while urinating, frequency/urgency, cloudy or foul-smelling urine, blood in urine, fever, nausea/vomiting, pain radiating to the groin, pregnancy status, and any history of stones or UTIs.