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What to do if…
you have sudden watery diarrhea after starting antibiotics and feel increasingly unwell

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

Short answer

Call NHS 111 now for urgent same-day advice, or use 111 online where it is available. Call 999 or go to A&E now if you are confused, difficult to wake, have sudden severe tummy pain, severe breathing difficulty, cold or blotchy skin, or feel dangerously unwell.

Do not do these things

  • Do not take medicines to stop diarrhoea, such as loperamide or Imodium, unless a clinician tells you to.
  • Do not rely on alcohol hand gel alone if C. difficile is possible; wash hands with soap and water.
  • Do not decide on your own whether to stop or continue the antibiotic while you are getting worse; get urgent advice before the next dose if you can do so safely.
  • Do not take leftover antibiotics, someone else’s antibiotics, or colon cleanse products.
  • Do not drive yourself to A&E if you feel faint, confused, very weak, or severely unwell.

What to do now

  1. Get urgent triage first.

    • Call 999 or go to A&E now if you are confused, difficult to wake, fainting or collapsing, have sudden severe tummy pain, severe breathing difficulty, cold or blotchy skin, or you feel dangerously unwell.
    • Otherwise, call NHS 111 now for same-day advice. Use 111 online where it is available, or phone 111 if you are unsure.
    • Ask for urgent advice today if you have diarrhoea while taking, or soon after taking, antibiotics; bloody diarrhoea; worsening weakness; dizziness on standing; repeated vomiting; or signs of dehydration.

  2. Say clearly that this started after antibiotics.

    • Give the name of the antibiotic, when you started it, and when you last took it.
    • Say how many watery stools you have had in the last 24 hours and whether it is getting worse.
    • Mention fever, tummy pain or cramps, blood, recent hospital or care home contact, a previous C. difficile infection, pregnancy, age over 65, a weakened immune system, or medicines that reduce stomach acid such as PPIs.
    • Say whether you are peeing less than normal, very thirsty, dizzy when standing, very weak, or unable to keep fluids down.

  3. Start rehydrating while you arrange care.

    • Take small, frequent sips of water or an oral rehydration drink.
    • Ask a pharmacist about oral rehydration sachets if you can do that without delaying urgent advice.
    • Escalate to 111 again, urgent care, 999, or A&E if you cannot keep fluids down, become confused or very drowsy, or feel much worse.

  4. Reduce spread at home until you have been assessed.

    • Wash your hands with soap and water after using the toilet and before preparing food.
    • Use a separate towel if you can.
    • Use a separate toilet if possible. If not, clean the toilet seat, flush handle, taps, and nearby high-touch surfaces after use with a household disinfectant or cleaning product used as directed.
    • Do not prepare food for other people if you can avoid it.

  5. Be ready for same-day next steps.

    • You may be asked for a stool sample if C. difficile is suspected.
    • Keep the antibiotic packet, your regular medicine list, and any recent discharge paperwork nearby.
    • Follow the plan you are given about whether to continue, pause, change, or stop any medicine.

What can wait

  • You do not need to work out the exact cause right now.
  • You do not need to decide today about probiotics, supplements, or a special diet.
  • You do not need to deep-clean your whole home now; focus on handwashing, towels, and bathroom surfaces.
  • You do not need to search for treatment options before getting urgent triage.

Important reassurance

Diarrhoea can happen with antibiotics and does not always mean C. difficile. Feeling increasingly unwell with watery diarrhoea after antibiotics is still a valid reason to get urgent help today, especially because dehydration can build up quickly.

Scope note

These are first steps for the next few hours only. Later decisions may need a GP, NHS 111 clinician, urgent care team, pharmacist, or hospital team, depending on your symptoms, risk factors, examination, and any stool test.

Important note

This is general information, not medical advice or a diagnosis. If you feel severely unwell, deteriorate quickly, become confused or very drowsy, or cannot keep fluids down, use urgent services and follow their instructions.

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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