The ankle-brachial index compares blood pressure at your ankle with blood pressure at your arm. It takes about fifteen minutes, involves no needles and no radiation, and it is the first-line test for peripheral artery disease.
What happens during the test
- You lie flat for about five to ten minutes so the pressures settle. This rest period is part of the test, not waiting room time.
- Blood pressure cuffs go on both arms and both ankles.
- A small handheld Doppler probe with gel is used to listen to the pulse while each cuff is inflated and released. It makes a whooshing sound.
- The highest ankle pressure for each leg is divided by the highest arm pressure. That ratio is the ABI, calculated separately for each leg.
It is no more uncomfortable than an ordinary blood pressure check. No fasting, no preparation, no need to stop medicines.
Reading the number
| ABI | Usually interpreted as |
|---|---|
| Above about 1.40 | Non-compressible vessels — the arteries are too stiff to squeeze. Not reassuring; a toe pressure is needed |
| About 1.00 to 1.40 | Normal range |
| About 0.91 to 0.99 | Borderline — an exercise ABI may be added |
| About 0.90 or below | Consistent with peripheral artery disease |
| Around 0.40 or below | Severe disease; significant concern for healing and for limb threat |
These ranges are the conventional thresholds, and they are a starting point rather than a verdict. What a number means depends on your symptoms, your other conditions, and whether there is a wound that needs to heal.
The most important limitation
A normal or high ABI does not always mean healthy arteries. In diabetes, chronic kidney disease and long-standing arterial disease, calcium in the vessel wall makes the ankle arteries hard to compress — so the cuff has to be inflated to a high pressure, and the ratio comes out normal or falsely elevated. A normal ABI in someone with real symptoms is a reason for more testing, not for reassurance.
The toe-brachial index
Toe arteries are much less prone to calcification, so a small cuff on the big toe gives a more trustworthy reading in exactly the groups where the ABI misleads. A TBI is routinely added when you have diabetes or kidney disease, when the ABI reads above about 1.40, or when the ABI looks normal but the clinical picture does not.
A toe-brachial index around 0.70 or above is generally considered normal. Absolute toe pressures also matter in their own right, particularly when a wound needs to heal — the question then is not just whether there is disease, but whether there is enough pressure for healing.
The exercise ABI
If your resting ABI is normal but your story is convincing, walking on a treadmill until symptoms appear and repeating the measurement can reveal a pressure drop that only happens under demand. A fall after exercise, in someone with a normal resting number, is a meaningful result.
What the ABI does not tell you
- Where the narrowing is — that needs ultrasound or other imaging.
- Anything about your veins. It is an arterial test. Swelling, varicose veins and clots are not what it measures.
- Anything about your nerves. Numbness and burning need sensory testing, which is a separate examination.
- Whether a wound will heal on its own — toe pressures and the clinical picture do more of that work.
Common questions
Can I do an ABI at home?
Not meaningfully. It needs a Doppler probe, the correct cuff sizes, a proper rest period and correct technique, and it is the kind of measurement where small errors change the category. Home blood pressure cuffs on the ankle do not produce a valid ABI. This is a fifteen-minute test in a clinic that has the equipment.
Does it hurt?
No more than a blood pressure check. The cuffs squeeze briefly. If you have rest pain or a painful wound, mention it beforehand — the technician can adjust how the test is done.
My ABI was 1.5. Is that good?
It is not a good result — it usually means the ankle arteries are too stiff to compress properly, which is itself a marker of disease. A high ABI should lead to a toe pressure rather than to reassurance.
Do I need to repeat it?
Often yes — to track change, after a procedure, or if symptoms alter. Because it is quick and non-invasive it is well suited to follow-up, and comparing against a previous number is frequently more informative than the number alone.
Can a podiatry office do this?
Some do and some refer for vascular studies. Ask the specific practice what they have in-house before the visit rather than assuming either way.
Where to go next
Sources
- National Heart, Lung, and Blood Institute. PAD — Diagnosis.
- American College of Cardiology. 2024 Lower Extremity PAD Guideline.
- Society for Vascular Surgery. Peripheral Artery Disease.
- MedlinePlus. Peripheral Arterial Disease.
Written by Tom Biernacki, DPM, FACFAS. Published 20 September 2026. General education, not medical advice. Interpretation of any result belongs with the clinician who knows your history.