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What to do if…
you develop sudden, wave-like flank pain that makes it hard to get comfortable

Produced and maintained by PanicStation.org Published: Last reviewed: Editorial policy UK guide

Short answer

Get urgent same-day medical advice now through NHS 111, your GP, or your local urgent NHS advice service. Call 999 or go to A&E now if you are confused, drowsy, faint, very weak, having difficulty speaking, or cannot travel safely.

Do not do these things

  • Do not try to sleep it off if you have fever, shivering, worsening pain, repeated vomiting, blood in your urine, or you have not passed urine all day.
  • Do not exceed the label dose of any pain medicine.
  • Do not take ibuprofen, naproxen, or another anti-inflammatory if you have been told to avoid them, may have a kidney infection, have kidney disease, are pregnant, take blood-thinning medicine, or have a stomach ulcer, unless a clinician says it is safe for you.
  • Do not drink alcohol or take recreational drugs to cope with the pain; they can make dehydration, drowsiness, and assessment harder.
  • Do not drive yourself if the pain is distracting, you feel faint, or you might need stronger pain relief; ask someone to take you or call 999 if you cannot travel safely.
  • Do not ignore burning when peeing, cloudy or bad-smelling urine, blood in urine, fever, or shivering.

What to do now

  1. Check for danger signs first. Call 999 or go to A&E now if:
    • you are confused, drowsy, faint, very weak, or having difficulty speaking
    • you feel seriously unwell and cannot travel safely
    • you cannot pass urine and you feel very unwell
  2. If you are not in immediate danger, still seek urgent same-day advice. Contact NHS 111, your GP, or your local urgent NHS advice service now if:
    • the pain is severe, hard to control, or comes in waves
    • you have a high temperature, feel hot, cold, sweaty, or shivery
    • you see blood in your urine
    • it burns or stings when you pee
    • you have pain in your side, lower back, groin, or under the ribs
    • you are repeatedly vomiting or cannot keep fluids down
    • you have not passed urine all day
    • you are pregnant, have a single kidney, have kidney disease, or have a weakened immune system
  3. Say the key words clearly when you ask for help. Use: “Sudden flank or loin pain, coming in waves, and I cannot get comfortable.” Add whether you have fever, shivering, vomiting, blood in urine, burning when peeing, pregnancy possibility, kidney disease, or a previous kidney stone.
  4. Write down three details for triage.
    • when the pain started and where it travels
    • when you last passed urine, and whether it was painful, bloody, cloudy, or bad-smelling
    • what pain relief you took, including the name and time
  5. Use cautious comfort measures while arranging care.
    • Sip water if you can keep it down, but do not force large amounts during severe pain or vomiting.
    • If you can take it safely, paracetamol may be used exactly as directed on the packet.
    • Avoid anti-inflammatory painkillers unless you know they are safe for you or a pharmacist, GP, NHS 111, or clinician has advised them.
    • A warm bath or heat pack on the sore side may help some people. Stop if it makes you feel faint, worse, or light-headed.
  6. Prepare for assessment. Bring your medicines list, allergies, key medical conditions, and any pregnancy information. Be ready to provide a urine sample if asked. Arrange transport because the pain can spike suddenly.

What can wait

  • You do not need to decide right now whether this is a kidney stone, kidney infection, pulled muscle, appendix problem, or something else.
  • You do not need to force lots of fluid while you are in severe pain or vomiting.
  • You do not need to plan scans, procedures, prevention, diet changes, or long-term follow-up today.
  • The first priority is getting urgent advice, controlling pain safely, and checking for infection or blockage.

Important reassurance

Wave-like flank or loin pain that makes it hard to get comfortable is a common reason to need urgent assessment. Getting help promptly is a protective step, especially because fever, shivering, vomiting, blood in urine, or trouble passing urine can change how quickly you need care.

Scope note

These are first steps for the next few hours only. Later decisions about tests, imaging, antibiotics, pain relief, procedures, or prevention need assessment by an appropriate clinician.

Important note

This is general information, not a diagnosis or medical advice. If symptoms are severe, worsening, or you feel unsafe, seek urgent medical care immediately.

Additional Resources

Closely connected guides that may be useful during the same situation or its immediate aftermath.

About this guide

This guide was produced and is maintained by PanicStation.org using its published editorial process. Official and specialist sources are checked where relevant, and AI-assisted tools may be used for drafting, organisation, and consistency checks. The site operator remains responsible for publication, revision, and removal decisions.

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