Anticoagulant
A medicine that reduces the blood's tendency to form clots.
What it means
An anticoagulant reduces the blood's ability to clot, to prevent clots forming or existing ones enlarging.
"Blood thinner" is the everyday term, though nothing is actually thinned.
Anticoagulants and antiplatelets are not the same thing, and the distinction is clinically important:
- Anticoagulants (warfarin, apixaban, rivaroxaban) act on clotting proteins. Used for atrial fibrillation, DVT and pulmonary embolism.
- Antiplatelets (aspirin, clopidogrel) stop platelets clumping. Used after heart attacks and strokes.
In practice
DOACs — direct oral anticoagulants — have largely replaced warfarin for most indications, needing no routine blood monitoring and having fewer food interactions.
Warfarin requires regular INR blood tests and is still preferred for mechanical heart valves.
Why it matters
Anyone taking an anticoagulant should tell every clinician, dentist and pharmacist before any procedure, and should carry an alert card.
A head injury while taking an anticoagulant needs assessment even if the person feels entirely well, because bleeding inside the skull can be delayed by hours.
We do not initiate or adjust anticoagulants remotely. We can review whether one is indicated and refer accordingly.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026