CoaglyWhat is a normal INR range? A plain-English chart
There is no single normal INR, and that trips up almost everyone who has just started warfarin. The number that counts as healthy depends entirely on why you are taking an anticoagulant — and for a lot of people, an INR that would be alarming in someone else is exactly where they are meant to be.
If you are not taking an anticoagulant
In a person who is not on a blood thinner, INR sits at roughly 0.8 to 1.2, and about 1.0 is treated as the reference point. INR is a standardised version of the prothrombin time — the seconds your blood takes to form a clot in the lab. Standardising it means a result from a hospital in one country means the same thing as a result from a clinic in another, which matters a great deal when the number is steering your dose.
Once you start warfarin, that baseline stops being the goal. Warfarin is supposed to push your INR up. A result of 1.1 while you are taking warfarin is not reassuring — it usually means the medication is not doing its job.
INR target range chart on warfarin
Ranges are set by your prescriber, and the table below reflects the targets used most commonly. Yours may differ for good reasons.
| Situation | Usual target INR | Midpoint aimed for |
|---|---|---|
| Atrial fibrillation | 2.0 – 3.0 | 2.5 |
| DVT or pulmonary embolism | 2.0 – 3.0 | 2.5 |
| Most mechanical heart valves | 2.5 – 3.5 | 3.0 |
| Mechanical mitral valve, or a valve plus extra risk factors | 2.5 – 3.5 or higher | 3.0+ |
| Some tissue valves, first months only | 2.0 – 3.0 | 2.5 |
| Antiphospholipid syndrome after a clot on treatment | Often 3.0 – 4.0 | 3.5 |
| Not on an anticoagulant | 0.8 – 1.2 | 1.0 |
Two things follow from this table. The first is that 2.5 is a good result for someone with atrial fibrillation and a low one for someone with a mechanical mitral valve. The second is that comparing your number with another patient's is close to meaningless unless you are being treated for the same thing.
How to find your own target range
Your range should be written on your anticoagulation record — the yellow book, the clinic card, the app your service uses, or the letter after your last appointment. If you cannot find it, ring the clinic and ask them to confirm it. It is a thirty-second phone call and it is the single most important number in your treatment, because every result you ever get is judged against it.
Ranges change
Target ranges are not permanent. Starting a new medication, a change in your heart rhythm, a planned operation or a new diagnosis can all move your target. When a clinician gives you a new range, write down the date it changed — old readings should be judged against the range that was in force at the time, not the new one.
What high and low actually mean
Below your range, your blood is clotting faster than intended. The risk being managed here is the one your warfarin was prescribed to prevent — a stroke, a clot in the leg or lung, a clot on a valve. Low readings rarely feel like anything, which is precisely the problem.
Above your range, your blood is clotting more slowly than intended and bleeding becomes easier. Most people feel nothing here either, though you may notice bruising you cannot account for, nosebleeds, gums bleeding when you brush, or periods that are heavier than usual.
Read the detail on each side in what a high INR means and what a low INR means.
Why one reading tells you less than you think
An INR result is a photograph, not a film. It tells you where you were on the morning of the blood draw, and warfarin moves slowly enough that the number can drift a long way between tests without anyone seeing it happen.
This is why anticoagulation clinics judge quality by time in therapeutic range — the share of days, not tests, that your estimated INR sat inside your target. Someone whose readings bounce between 1.6 and 3.8 and someone who sits quietly at 2.4 can both average 2.5. They are not in the same clinical position, and TTR is what separates them. Above 70% is generally considered good control, and below 60% is where clinicians start to look for what is going wrong.
You can work out your own figure right now with our free time in therapeutic range calculator — enter your past results and it applies the same Rosendaal method the clinics use.
Tracking your range in Coagly
Coagly asks for your target range once, during setup, and then does the comparison for you every time. Log a result and you get the number, a plain-language label — in range, below, above — and where it falls on your band, in colour and in words, never colour alone. Nothing is guessed: if a value was never recorded, Coagly says so rather than filling the gap with a plausible-looking number.
If your clinic changes your target, you update it once and every future reading is judged against the new band. Your time in therapeutic range is calculated in the background from the readings you have already entered, so the measure your clinic actually cares about is on your home screen instead of buried in a spreadsheet.
Common questions
Is an INR of 2.5 good?
For most people taking warfarin for atrial fibrillation, a DVT or a pulmonary embolism, 2.5 is the middle of the usual 2.0 to 3.0 target and is a good result. For someone with a mechanical mitral valve whose target is 2.5 to 3.5, the same 2.5 sits right at the bottom edge of range. Whether a number is good depends on the range you were given, not on the number alone.
What INR is dangerous?
Bleeding risk climbs noticeably above 4.0 to 5.0, and an INR above 5.0 warrants contacting your clinic the same day even if you feel completely well. On the other side, an INR near 1.0 while taking warfarin means you have very little anticoagulant protection. Both directions need a clinician, not a self-adjustment.
Why does my INR change when nothing has changed?
Warfarin is unusually sensitive to ordinary life. Vitamin K in your diet, a course of antibiotics, alcohol, illness with fever or diarrhoea, a new supplement and even a change in how well you absorb food can all move it. Recording a short note alongside each reading is often what lets you and your clinic spot the pattern later.
Does a home INR meter give the same number as the lab?
Home meters are accurate enough to steer treatment and are widely used, but a small difference from the lab value is normal, particularly at higher INRs. Clinics usually check a meter against a lab draw when you start self-testing. What matters most is consistency — record which device produced each reading.