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uk Health & medical scares blood thinners new headache • anticoagulant headache and bruising • warfarin unexplained bruises • doac bruising for no reason • apixaban bruising and headache • rivaroxaban new headache • dabigatran easy bruising • edoxaban bruising concern • sudden severe headache on anticoagulant • headache after bump on blood thinners • unexplained large bruises • bruises getting bigger • possible internal bleeding signs • bleeding risk blood thinner • anticoagulant side effects worry • warfarin inr too high symptoms • new headache not like usual • bruising without injury • blood thinner safety check

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

Short answer

Treat this as urgent. If the headache is sudden/severe, you have any stroke-like symptoms, or you’ve had a recent head knock/fall, call 999 or go to A&E now.

Do not do these things

  • Do not ignore a new or unusual headache while on blood thinners, especially if it’s getting worse.
  • Do not take aspirin or NSAIDs such as ibuprofen (and similar anti-inflammatories) unless a clinician has already told you it’s safe with your anticoagulant.
  • Do not start any new over-the-counter medicines (including cold/flu products) or herbal supplements without checking with a pharmacist/clinician first.
  • Do not drive yourself to get help if you feel faint, confused, or your vision/speech is affected.
  • Do not stop or skip doses “just in case” without urgent clinical advice. If you’re being sent to A&E/999 for suspected serious bleeding, do not take further doses unless a clinician tells you to, and bring the medicine with you.

What to do now

  1. Check for emergency red flags (act immediately if any apply).
    Call 999 (or go to A&E) if you have:

    • a sudden, very severe headache, or the “worst” headache you’ve had
    • confusion, collapse, fainting, severe drowsiness, seizure
    • weakness/numbness on one side, face droop, trouble speaking, vision changes, new imbalance
    • a headache after a fall, bump, or blow to the head (even if you felt “OK” at the time)
    • bleeding you can’t control, vomiting blood/“coffee grounds”, black/tarry poo, or red/pink/brown urine

  2. If it’s not an emergency, get urgent clinical advice today.

    • Call NHS 111 now, or contact your GP / local anticoagulation clinic if you’re under one.
    • Say clearly: “I’m on a blood thinner and I have a new headache and/or unexplained bruising.”

  3. Work out which blood thinner you’re on and when you last took it (so you can tell the clinician).

    • Warfarin? Apixaban? Rivaroxaban? Dabigatran? Edoxaban?
    • Note the dose and the time of the last dose.

  4. If you take warfarin, expect they may want an urgent INR check.

    • Have your INR record/booklet (often a “yellow book”) or app/clinic details ready.
    • Mention any recent missed/double doses, illness with vomiting/diarrhoea, or new medicines (especially antibiotics) or supplements.

  5. Quickly scan for other bleeding clues you might not have linked to this.
    Look for: bleeding gums, frequent nosebleeds, unusually heavy periods, bruises that are larger than expected, appear without injury, or keep growing, plus blood in vomit/poo/urine or unusual dizziness/weakness.

  6. Make it safer while you wait for help.

    • Avoid falls/knocks: sit down if dizzy, avoid stairs/risky tasks.
    • If possible, ask someone to stay with you.
    • Gather medication packets and any anticoagulant alert card you have.

What can wait

  • You do not need to figure out the exact cause of the headache or bruises right now.
  • You do not need to decide whether you should stop anticoagulation long-term — that decision should be made with a clinician based on your clotting risk.
  • You do not need to “test” the headache with painkillers first (some are unsafe with anticoagulants).
  • You do not need to contact multiple services at once: one urgent clinical contact (111/GP/anticoag clinic) is enough unless red flags develop.

Important reassurance

It’s common to feel alarmed by a new headache or unexpected bruising on blood thinners. Many causes are treatable, and getting advice early is the safest way to prevent serious bleeding complications without making risky medication changes in panic.

Scope note

This guide covers first steps only for the next few hours. Ongoing decisions (dose changes, switching anticoagulants, investigating bruising) may need your GP, anticoagulation clinic, or hospital team.

Important note

This is general information, not medical diagnosis or personal medical advice. If symptoms are severe, sudden, worsening, or you’re unsure, choose the safer option and seek urgent care.

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