PanicStation.org
UK USA
uk Health & medical scares

What to do if…
you are on blood thinners and develop a new headache or unexplained bruising

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

Short answer

A new or unusual headache, severe bruising, or unexplained bruising while taking a blood thinner needs same-day clinical advice. Call 999 now if the headache is sudden or severe, you have stroke-like symptoms, you have had a head injury, or there are signs of serious bleeding.

Do not do these things

  • Do not ignore a new, unusual, worsening, or severe headache while taking a blood thinner.
  • Do not drive yourself to A&E if you may be having stroke symptoms, feel faint or confused, or your vision, speech, balance, or strength is affected.
  • Do not take aspirin, ibuprofen, naproxen, diclofenac, or other anti-inflammatory painkillers unless a doctor or pharmacist has told you they are safe with your blood thinner.
  • Do not start cold and flu remedies, herbal remedies, vitamins, or supplements without checking with a pharmacist or clinician.
  • Do not take extra doses to “catch up”.
  • Do not stop, skip, or change doses in panic. If you think you may have serious bleeding, ask 999, A&E, NHS 111, your GP, or your anticoagulation clinic what to do about your next dose.

What to do now

  1. Call 999 now if any emergency sign applies.
    This includes:

    • a sudden, very severe headache, or the worst headache you have had
    • face drooping, arm weakness, one-sided numbness or weakness, trouble speaking, confusion, new vision loss, new imbalance, collapse, seizure, or severe drowsiness
    • a headache after a fall, bump, blow to the head, or other head injury
    • bleeding that will not stop
    • vomiting blood or material that looks like coffee grounds
    • black or tarry poo, red poo, or red, pink, or brown urine
    • severe dizziness, faintness, unusual weakness, or looking very pale with bleeding or bruising

  2. If you hit your head but feel mostly OK, still get urgent advice today.
    Tell 111 if it is available where you are, your local urgent medical advice service, your GP, your anticoagulation clinic, or A&E that you are on a blood thinner and have had a head injury. People on anticoagulants may need assessment even when symptoms seem mild.

  3. If there are no emergency signs, contact one urgent service now.
    Use NHS 111 if available where you are, your local urgent medical advice service, your GP, or your anticoagulation clinic if you have one. Say clearly: “I take a blood thinner and I have a new headache, unexplained bruising, or bruises that are getting bigger.”

  4. Get the medicine details ready.
    Find the packet, bottle, alert card, or app record. Be ready to say:

    • the name of the blood thinner, such as warfarin, apixaban, rivaroxaban, dabigatran, or edoxaban
    • the dose
    • when you last took it
    • whether you have missed a dose, taken an extra dose, or taken the wrong dose

  5. If you take warfarin, have your INR details ready.
    Find your INR booklet, yellow book, clinic letter, app, or recent result if you have it. Tell the clinician about recent antibiotics, new medicines, vomiting, diarrhoea, illness, alcohol changes, missed doses, or double doses.

  6. Check for bleeding clues before you speak to someone.
    Look for bleeding gums, frequent nosebleeds, unusually heavy periods, bruises that appear without injury, bruises that are larger than expected, bruises that keep spreading, blood in vomit, blood in poo, blood in urine, or unusual dizziness or weakness.

  7. Make the next hour safer.
    Sit down if you feel dizzy. Avoid stairs, ladders, sharp tools, heavy lifting, sport, or anything where a fall or knock is more likely. If possible, ask someone to stay nearby while you get advice.

  8. Bring the blood thinner with you if you are told to go in.
    Take the medicine packet, anticoagulant alert card, INR details if relevant, and a list of other medicines, including over-the-counter medicines and supplements.

What can wait

  • You do not need to work out the exact cause of the headache or bruising right now.
  • You do not need to decide whether blood thinners are right for you long-term.
  • You do not need to search for every possible side effect before asking for help.
  • You do not need to contact several services at once. Use one urgent medical advice route unless symptoms worsen or emergency signs appear.
  • You do not need to try painkillers first. Some painkillers can increase bleeding risk with blood thinners.

Important reassurance

New symptoms on blood thinners can feel frightening, but asking for advice early is a sensible safety step. Many causes of headache or bruising are manageable, and getting checked helps avoid risky decisions such as changing the medicine on your own.

Scope note

These are first steps only for the next few hours. Later decisions about INR checks, scans, dose changes, switching medicines, or investigating bruising may need your GP, anticoagulation clinic, pharmacist, or hospital team.

Important note

This is general information, not medical diagnosis or personal medical advice. If symptoms are sudden, severe, worsening, linked to a head injury, or you are unsure, choose urgent help.

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.

Support us