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uk Health & medical scares sudden flank pain • pain in side of back • pain comes in waves • can’t get comfortable • cramping side pain • severe one-sided back pain • pain radiating to groin • nausea with flank pain • vomiting with side pain • possible kidney stone pain • possible renal colic • blood in urine concern • pain with peeing • fever with back pain • shivering with pain • can’t pass urine • urgent same-day assessment • sudden abdominal side pain • one-sided lower rib pain • sudden loin pain

What to do if…
you develop sudden flank pain that comes in waves and makes it hard to get comfortable

Short answer

Get urgent same-day medical advice: contact NHS 111 (or your GP) now, and go to A&E immediately if the pain is severe/uncontrolled, you have fever/shivering, you cannot pass urine, or you’re vomiting repeatedly.

Do not do these things

  • Do not “wait it out” if you have fever/feel hot and shivery, worsening pain, persistent vomiting, or you cannot pass urine.
  • Do not exceed the label dose of any pain medicine. Do not take two anti-inflammatories (NSAIDs) together (for example ibuprofen plus naproxen). If you’re unsure what’s safe for you, ask NHS 111 or a pharmacist.
  • Do not drink alcohol or take recreational drugs to cope — they can worsen dehydration and make assessment harder.
  • Do not drive yourself to get help if you feel faint, drowsy, or are in distracting pain — ask someone to take you or call 999 if you can’t travel safely.
  • Do not ignore new blood in your urine, burning when peeing, or feeling generally unwell — these can change how urgently you need to be seen.

What to do now

  1. Do a 60-second safety check. If you have any of the following, go to A&E now or call 999 if you can’t get there safely:
    • pain that is severe or not settling with simple measures
    • a high temperature, or you feel hot, cold, sweaty, or shivery
    • you are unable to pass urine (or you’re passing very little)
    • repeated vomiting so you can’t keep fluids down
    • you are pregnant, immunocompromised, have a single kidney, or significant kidney disease
  2. If you don’t have the red flags above, but the pain is still wave-like and hard to sit still with: contact NHS 111 for urgent same-day advice (or your GP if they can see you urgently). Say: “sudden flank/loin pain in waves, can’t get comfortable,” and mention any nausea/vomiting, urinary symptoms, pregnancy possibility, or kidney history.
  3. Write down three details for triage (it speeds things up):
    • your temperature (if you can check it)
    • when you last passed urine and whether it was painful or bloody
    • what pain relief you’ve taken (name + time)
  4. Use safer comfort measures while you arrange care.
    • If you can take them safely, use over-the-counter pain relief exactly as directed on the packet (avoid anything you’re allergic to or have been told not to take).
    • A warm bath or heat pack on the sore side can help some people. Stop if it makes you feel worse or light-headed.
  5. Prepare to be assessed. If you’re going to urgent care/A&E:
    • bring a list of medicines, allergies, and key conditions
    • be ready to provide a urine sample
    • arrange transport (pain can spike suddenly)

What can wait

  • You do not need to decide right now what the cause is (kidney stones are one possibility, but not the only one).
  • You do not need to force large amounts of fluid during severe pain or active vomiting.
  • You do not need to plan follow-up tests or long-term prevention today; first priority is ruling out infection/obstruction and getting pain controlled.

Important reassurance

Wave-like flank/loin pain that makes you restless and unable to get comfortable is a common reason for urgent assessment. Getting checked promptly is a sensible, protective step — especially because infection with blockage needs fast treatment.

Scope note

This is first-steps-only guidance for the next few hours. Further decisions (tests, imaging, antibiotics, procedures, prevention) depend on what clinicians find.

Important note

This is general information, not a diagnosis. If you are worried, symptoms are severe, or you have fever/shivering, persistent vomiting, or trouble passing urine, seek urgent medical care immediately.

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