DOACs vs warfarin: how they differ, who gets which, and what to counsel
10 November 2026 · 8 min read · By the PharmacySkills team
If you work in a pharmacy for more than a week, someone will ask you about DOACs vs warfarin. A patient switched from warfarin to apixaban wants to know why. A GP wants to know which DOAC suits a frail 84-year-old. An exam question hands you a creatinine, a weight and an age and asks for the right dose. This guide walks through what actually differs between the two groups, when warfarin is still the better drug, and the counselling points that keep patients safe.
What both groups are trying to do
Every anticoagulant has the same job: stop clots forming where they shouldn't, without causing too much bleeding. In atrial fibrillation (AF) the upper chambers of the heart quiver instead of squeezing, blood pools, and clots form that can travel to the brain and cause a stroke. In deep vein thrombosis (DVT) and pulmonary embolism (PE), clots form in the veins and can travel to the lungs.
The difference between the two groups is where in the clotting chain they act.
- Warfarin is a vitamin K antagonist. The liver needs vitamin K to make working versions of clotting factors II, VII, IX and X. Warfarin blocks the recycling of vitamin K, so over several days the blood runs short of those factors. Because it works indirectly, its effect is slow to start, slow to wear off and very sensitive to diet, illness and other drugs. That is why it needs INR monitoring (covered in detail in our warfarin and the INR guide).
- DOACs (direct oral anticoagulants) block one clotting factor directly. Apixaban, rivaroxaban and edoxaban block factor Xa. Dabigatran blocks thrombin (factor IIa). A direct block means a predictable effect within a few hours, a short half-life, and no routine blood test to adjust the dose.
DOACs vs warfarin at a glance
| Warfarin | DOACs | |
|---|---|---|
| How it works | Stops vitamin K recycling, lowering factors II, VII, IX, X | Directly blocks factor Xa (apixaban, edoxaban, rivaroxaban) or thrombin (dabigatran) |
| Onset | Several days; often needs a loading regimen | Within a few hours |
| Monitoring | Regular INR checks, dose changes | No INR; renal function, liver function, full blood count and weight at least yearly |
| Dosing | Variable, adjusted to INR | Fixed dose, reduced for certain patient factors |
| Food | Big swings in vitamin K intake change the INR | Mostly not affected (rivaroxaban 15 mg and 20 mg must be taken with food) |
| Interactions | Many (antibiotics, azoles, enzyme inducers, alcohol, cranberry) | Fewer, but important with strong CYP3A4 and P-glycoprotein inhibitors or inducers |
| Missed doses | Long half-life gives some forgiveness | Short half-life, so a missed dose quickly leaves the patient unprotected |
| Reversal | Vitamin K and prothrombin complex concentrate | Idarucizumab (dabigatran); andexanet alfa (apixaban, rivaroxaban) |
| Kidneys | Fine in severe renal impairment | All need dose checks against creatinine clearance; avoided in the most severe impairment |
What NICE says about choosing
For AF, NICE guideline NG196 says to offer a DOAC to people with a CHA2DS2-VASc score of 2 or more, and to consider one in men with a score of 1, taking bleeding risk into account. Apixaban, dabigatran, edoxaban and rivaroxaban are all listed as options. A vitamin K antagonist such as warfarin is offered when a DOAC is contraindicated, not tolerated or not suitable. NICE recommends the ORBIT score, rather than older tools, to assess bleeding risk.
NICE does not pick a single DOAC. In practice your local integrated care board will have a preferred choice, usually based on price and on the patient in front of you. Apixaban is often first line because it is twice daily (a missed dose leaves a smaller gap), works in a wide range of kidney function and has a good bleeding profile in trials. Once-daily rivaroxaban or edoxaban can suit people who struggle with twice-daily medicines or need a carer or compliance aid.
For DVT and PE, NICE guideline NG158 also makes apixaban or rivaroxaban the usual first choice.
When warfarin is still the right drug
This is where exam questions like to catch people. DOACs are not suitable for everyone, and warfarin (or another option) is still preferred in these situations:
- Mechanical heart valves. Dabigatran caused more clots and more bleeding than warfarin in this group in trials. DOACs should not be used.
- Moderate to severe mitral stenosis. Patients with this valve problem were excluded from the major DOAC trials, so warfarin remains standard.
- Antiphospholipid syndrome, especially in people who test positive for all three antibodies. The MHRA warned in 2019 that DOACs are not recommended here because of a higher rate of clots compared with warfarin.
- Severe renal impairment. With a creatinine clearance below 15 mL/min, DOACs are generally avoided (dabigatran below 30 mL/min).
- Interacting drugs that can't be changed, such as rifampicin, carbamazepine, phenytoin or St John's wort, which can drop DOAC levels, or some HIV and antifungal treatments that can raise them.
- Pregnancy and breastfeeding. DOACs should be avoided; low molecular weight heparin is normally used in pregnancy instead.
A patient who is stable on warfarin, with a good time in therapeutic range and no wish to change, can stay on it. Switching is a conversation, not a rule.
DOAC doses in atrial fibrillation
These are the standard stroke prevention doses for non-valvular AF. Always check the BNF and the product's SmPC, because doses for DVT and PE treatment are different and include an initial higher-dose phase.
| DOAC | Usual dose | Reduced dose and when |
|---|---|---|
| Apixaban | 5 mg twice daily | 2.5 mg twice daily if 2 or more of: age 80 or over, weight 60 kg or less, serum creatinine 133 micromol/L or more. Also 2.5 mg twice daily if creatinine clearance is 15 to 29 mL/min |
| Rivaroxaban | 20 mg once daily with food | 15 mg once daily with food if creatinine clearance is 15 to 49 mL/min |
| Edoxaban | 60 mg once daily | 30 mg once daily if any one of: creatinine clearance 15 to 50 mL/min, weight 60 kg or less, or taking ciclosporin, dronedarone, erythromycin or ketoconazole |
| Dabigatran | 150 mg twice daily | 110 mg twice daily if age 80 or over, or taking verapamil. Consider 110 mg for ages 75 to 80, creatinine clearance 30 to 50 mL/min, gastritis or reflux, or high bleeding risk |
Notice the trap with apixaban: one criterion is not enough. Underdosing is a well-known problem in practice, and a patient given 2.5 mg twice daily when they only meet one criterion is less protected against stroke. Edoxaban works the other way round: one criterion is enough.
Worked example: getting the renal check right
DOAC dosing uses creatinine clearance calculated with the Cockcroft-Gault equation, not the eGFR printed on the blood result. eGFR is standardised to an average body size and can overestimate kidney function in older, lighter patients, which are exactly the people at most risk of bleeding.
Mrs A is 78, weighs 52 kg and has a serum creatinine of 140 micromol/L. She has AF and is starting apixaban.
Cockcroft-Gault for a woman: CrCl = (140 minus age) x weight x 1.04 / serum creatinine
CrCl = (140 minus 78) x 52 x 1.04 / 140 = 62 x 52 x 1.04 / 140 = about 24 mL/min
Now check the dose. Her creatinine clearance is in the 15 to 29 band, so apixaban 2.5 mg twice daily is indicated on that alone. She also meets two of the three criteria (weight 60 kg or less, creatinine 133 or more), which points the same way. If she were on rivaroxaban, the dose would be 15 mg once daily. Dabigatran would be contraindicated.
Which weight to use for very heavy or very light patients varies between local guidelines, so follow your trust's policy. If you want more practice with this formula, it appears in our GPhC calculations worked examples.
Counselling points for DOACs
Many patients have heard about warfarin from relatives and assume DOACs work the same way. The key messages:
- Take it at the same time every day, and don't stop without talking to the prescriber. Protection fades within a day of stopping, so the stroke risk returns quickly.
- Missed doses: don't take two doses to make up. The exact rule differs by drug (for example, a twice-daily dose can be taken if remembered within a few hours), so check the patient leaflet for their specific DOAC.
- Rivaroxaban 15 mg and 20 mg must be taken with food, or much less is absorbed. The MHRA issued a reminder about this.
- Dabigatran capsules must be swallowed whole, not opened, because opening them greatly increases absorption. They need to stay in the original pack to keep out moisture, so they don't go in a compliance aid.
- Bleeding signs to report: blood in urine, black or tarry stools, coughing or vomiting blood, nosebleeds that won't stop, unusual bruising, and any head injury (go to A&E even if they feel fine).
- Avoid over-the-counter NSAIDs like ibuprofen and aspirin unless prescribed. Paracetamol is the usual choice for pain. Check any herbal products, especially St John's wort.
- Carry an anticoagulant alert card and tell dentists, pharmacists and anyone doing a procedure.
- Blood tests still happen, just not INRs. Kidney function, liver function and full blood count are checked at least yearly, and more often in older people or when kidney function is reduced.
Switching from warfarin to a DOAC
Stop warfarin and start the DOAC once the INR has fallen to a safe level. The thresholds differ:
- Apixaban and dabigatran: when INR is below 2
- Edoxaban: when INR is 2.5 or below
- Rivaroxaban (AF): when INR is 3 or below
Starting too early stacks two anticoagulants on top of each other. Starting too late leaves a gap.
Exam tips: key points to remember
- Mechanism: warfarin is indirect (vitamin K); DOACs are direct (Xa or thrombin).
- Valves and APS: mechanical valve, moderate to severe mitral stenosis or antiphospholipid syndrome means warfarin, not a DOAC.
- Apixaban needs 2 of 3 (80, 60 kg, 133); edoxaban needs only 1.
- Cockcroft-Gault creatinine clearance, not eGFR, for DOAC dosing.
- Rivaroxaban with food; dabigatran whole and in its original pack.
- Reversal: idarucizumab for dabigatran; andexanet alfa for apixaban and rivaroxaban; vitamin K and prothrombin complex for warfarin.
The PharmacySkills course covers anticoagulants in more depth, with lessons and practice questions you can work through at your own pace.
Sources: BNF (apixaban, rivaroxaban, edoxaban, dabigatran etexilate and warfarin monographs); NICE NG196 Atrial fibrillation: diagnosis and management; NICE NG158 Venous thromboembolic diseases; NICE CKS Anticoagulation: oral; MHRA Drug Safety Update: DOACs not recommended in antiphospholipid syndrome (2019) and rivaroxaban 15 mg and 20 mg tablets to be taken with food.
This article is for revision and education. Always check the current BNF, NICE guidance and your local policies before applying it in practice.