Anticoagulants prevent and treat blood clots in conditions such as atrial fibrillation, deep vein thrombosis, pulmonary embolism and mechanical heart valves. They save lives, but they are also among the medicines most often involved in serious harm. The Institute for Safe Medication Practices lists anticoagulants as high-alert medications. Nurses give them, monitor patients and teach them how to stay safe.
Types
| Drug | How it’s given | Monitoring | Reversal |
|---|---|---|---|
| Warfarin | Oral, once daily, dose varies | INR blood tests | Vitamin K; prothrombin complex concentrate for major bleeding |
| DOACs (apixaban, rivaroxaban, edoxaban, dabigatran) | Oral, fixed doses | No routine INR; kidney function | Specific agents for some (e.g. idarucizumab for dabigatran, andexanet alfa for some anti-Xa drugs) where available |
| Low molecular weight heparin (enoxaparin, dalteparin) | Subcutaneous injection | Weight and kidney function; platelets | Protamine (partial) |
| Unfractionated heparin | IV infusion or SC | aPTT | Protamine |
Warfarin and the INR
- The INR measures how long blood takes to clot. Normal without warfarin is about 1.0.
- Target INR is usually 2.0–3.0 for most indications (e.g. AF, DVT, PE); higher for some mechanical heart valves, as specified by the prescriber.
- INR is affected by diet (sudden changes in vitamin K-rich foods such as leafy green vegetables), alcohol, illness, and many medicines, including antibiotics, antifungals, amiodarone, some anticonvulsants and herbal remedies.
- Always check the latest INR and the prescribed dose before giving warfarin.
Giving LMWH injections
- Check weight-based dose and kidney function.
- Inject subcutaneously into the abdomen (at least 5 cm from the umbilicus), rotating sites. Don’t expel the air bubble from pre-filled syringes and don’t rub the site.
- Check platelets as per policy (heparin-induced thrombocytopenia is rare but serious).
Signs of bleeding
- Bleeding gums, nosebleeds, easy bruising.
- Blood in urine; black or bloody stools; vomiting blood. See our GI bleeding guide.
- Heavy periods.
- Severe headache, confusion, weakness: possible brain bleed. An emergency, especially after any fall or head injury. See our head injury guide.
- Falling haemoglobin, rising pulse, falling BP.
Before procedures
Anticoagulants usually need to be paused or adjusted before surgery, biopsies, lumbar punctures and some injections. Always flag anticoagulant use and follow the specific plan from the prescriber. Never stop or restart without instructions.
Patient education
- Why they take it, and the importance of taking it at the same time every day.
- What to do if a dose is missed (depends on the drug).
- Carry an anticoagulant alert card.
- Tell every health worker, dentist and pharmacist that they take an anticoagulant.
- Avoid NSAIDs (ibuprofen, diclofenac) and check before starting any new medicine or herbal remedy.
- Warfarin: keep diet consistent, limit alcohol, attend INR checks.
- Recognise bleeding signs and when to seek urgent help.
Related: Rights of medication administration · Stroke · Atrial fibrillation on ECG
Based on NICE guidance on anticoagulation, BNF information and ISMP high-alert medication guidance. Educational content: follow your prescription and local policy.