Drug Class Guide
Blood Thinners (Anticoagulants)
Medicines that prevent dangerous clots, most often to prevent stroke in atrial fibrillation and to treat clots in the legs or lungs.
How Blood Thinners Work
Anticoagulants do not actually thin the blood. They slow the chain of clotting proteins so clots form less easily. The newer direct oral anticoagulants (DOACs) block a single clotting factor, either factor Xa or thrombin, while warfarin lowers several vitamin K-dependent factors at once. Antiplatelet drugs such as aspirin and clopidogrel work differently, by keeping platelets from clumping.
What Blood Thinners Treat
- Stroke prevention in atrial fibrillation
- Blood clots in the lungs
- Deep vein thrombosis (leg clots)
- Clot prevention after hip or knee replacement
Blood Thinners in Our Medication Guide
- ApixabanEliquisFactor Xa inhibitor taken twice daily; stroke prevention in AFib and blood clots.
- RivaroxabanXareltoFactor Xa inhibitor taken once daily for most uses; some doses must be taken with food.
- DabigatranPradaxaDirect thrombin inhibitor taken twice daily; has a specific reversal drug.
- EdoxabanSavaysaFactor Xa inhibitor taken once daily; less effective in AFib when kidney function is very high.
- WarfarinCoumadin, JantovenThe oldest oral option; needs regular INR blood tests and is required for mechanical heart valves.
- EnoxaparinLovenoxInjectable heparin; used around surgery, in hospitals and during pregnancy.
- FondaparinuxArixtraInjectable; prevents and treats blood clots.
Common Side Effects
Bleeding is the main risk: easier bruising, nosebleeds, bleeding gums, and less often blood in the urine or stool or bleeding in the brain. For most people with atrial fibrillation, the stroke protection outweighs this risk by a wide margin.
Important Cautions
- Avoid NSAIDs such as ibuprofen and naproxen unless your doctor approves; they add to bleeding risk.
- Tell every doctor and dentist that you take a blood thinner. Do not stop it on your own; stopping raises the risk of stroke and clots.
- Warfarin interacts with many drugs and with changes in vitamin K from leafy greens; keep your diet steady rather than avoiding them.
- Seek emergency care for a severe headache, vomiting blood, black stools or a serious fall.
Common Questions About Blood Thinners
Are Eliquis and Xarelto better than warfarin?
For most people with atrial fibrillation not caused by a heart valve problem, guidelines prefer a DOAC over warfarin. DOACs cause fewer brain bleeds, need no routine INR checks and have fewer food interactions. Warfarin is still the right choice for mechanical heart valves and moderate to severe mitral stenosis, and it costs less.
Can a blood thinner be reversed in an emergency?
Yes. Warfarin is reversed with vitamin K and clotting-factor concentrates, dabigatran with idarucizumab, and apixaban and rivaroxaban with clotting-factor concentrates or a specific reversal agent. Emergency departments also treat bleeding with supportive care while the drug wears off.
Is aspirin a blood thinner?
Aspirin is an antiplatelet drug, not an anticoagulant. It keeps platelets from clumping and is used after heart attacks and stents, but it does not prevent stroke in atrial fibrillation nearly as well as an anticoagulant. Taking both raises bleeding risk, so do not add aspirin without asking your doctor.
This guide is general information, not a substitute for advice about your own medicines. Do not start, stop or switch a medication without talking with your doctor. Questions about a prescription? Our internal medicine team can help.
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