Ankle-Brachial Index: The Test Before Compression

An ankle brachial index, or ABI, compares the blood pressure at your ankle to the blood pressure in your arm. Divide the first by the second and you get a number for each leg. A result of 1.00 to 1.40 is normal. A result of 0.90 or below means blood is not reaching the lower leg the way it should, and is consistent with peripheral artery disease. The test is short, painless, and involves no needles.

It is also the number that decides whether compression therapy is safe for a given leg, which is why we ask about it before we fit anyone.

September is Vascular Disease Awareness Month. This article is written for two readers: patients who have been told to get an ABI and want to know what it is, and referring clinicians who want a plain reference to hand a patient. If you would rather ask a question directly, Lumi, our 24/7 chatbot, is at the bottom right of every page on mcbdme.com.

The quick answer

• What it measures: ankle systolic pressure divided by arm systolic pressure, done on both legs.
• What happens: you lie flat and rest for a while, cuffs go on both arms and both ankles, a small handheld Doppler finds the pulse, and the clinician records the pressures. No needles, no dye, no radiation.
• The number that matters: 0.90 or below is consistent with PAD. 0.91 to 0.99 is borderline. 1.00 to 1.40 is normal. Above 1.40 means the arteries are too stiff to compress, which is its own finding.
• Who orders it: primary care, vascular surgery, podiatry, cardiology, and wound care all order ABIs routinely.
• Why we ask about it: compression is the correct treatment for venous and lymphatic swelling and can cause harm on a leg with poor arterial flow. The ABI is how that gets settled.
• It is not the whole picture. A normal ABI at rest does not always rule out PAD, and in diabetes the number can read falsely high.

Everything below explains how this works in practice.

What the test actually is

You lie flat on your back and rest first, because standing or sitting changes the pressures. Then a standard blood pressure cuff goes on each upper arm and each ankle.

Instead of a stethoscope, the clinician uses a small handheld Doppler, a pen-sized probe with gel on the tip that makes the sound of blood flow audible. It gets placed over the artery on the top of the foot (dorsalis pedis) and behind the inner ankle bone (posterior tibial), and over the brachial artery in each arm. The cuff inflates until the sound stops, then deflates slowly until it returns. That pressure is the systolic reading for that spot.

For each leg, the highest ankle pressure is divided by the higher of the two arm pressures. Each leg gets its own ABI, and the two can differ substantially. Cleveland Clinic has a good patient-level walkthrough of the procedure, and notes that the blood pressure measurements typically take 10 to 20 minutes after a rest period beforehand.

You keep your clothes on apart from rolling up sleeves and trouser legs. It does not hurt beyond the ordinary squeeze of a blood pressure cuff. The Society for Vascular Surgery describes it simply as a non-invasive test that uses inflatable cuffs to gauge circulation.

Some offices also run an exercise ABI, where you walk on a treadmill and the ankle pressures are repeated immediately afterward. This catches people whose resting numbers look acceptable but whose arteries cannot keep up under demand. If you have classic walking pain and a normal resting ABI, this is the test to ask about.

Reading the number

The normal, borderline, abnormal, and non-compressible ranges come from the 2024 ACC/AHA peripheral artery disease guideline, which reports a resting ABI as abnormal at 0.90 or below, borderline at 0.91 to 0.99, normal at 1.00 to 1.40, and non-compressible above 1.40. The National Heart, Lung, and Blood Institute describes an ABI below about 0.40 as a sign of severe PAD.

Two things people misread about this table.

A single number is not a diagnosis. It is one input alongside your symptoms, your pulses, your risk factors, and sometimes imaging. A borderline ABI in someone with no symptoms and no risk factors means something different than the same number in a 68-year-old smoker with diabetes.

Left and right are separate. It is common to have a normal ABI on one side and an abnormal one on the other. Ask for both numbers, not "the" number.

The falsely high result

This is the part worth understanding if you have diabetes or kidney disease.

The ABI works by squeezing an artery closed with a cuff. If the artery walls have become stiff and calcified, the cuff cannot compress them properly, so it takes an unusually high pressure to stop the flow. The math then produces a high number, sometimes above 1.40, on a leg that may in fact have serious arterial disease.

Medial arterial calcification is common in long-standing diabetes, chronic kidney disease, and advanced age. Cleveland Clinic notes that a high ABI can reflect stiff, calcified vessels from age or diabetes, and that when arteries are calcified, an ABI test cannot reliably diagnose PAD.

When that happens, the usual next step is a toe-brachial index. The small vessels in the toes calcify far less, so a cuff around the big toe gives a more trustworthy reading. Under the 2024 guideline, a TBI of 0.70 or below is considered abnormal.

The practical takeaway: if you have diabetes and someone tells you your ABI is fine, it is reasonable to ask whether the number was above 1.40, and whether a toe pressure should be checked.

Why we ask about arterial status before a compression fitting

Compression garments work by applying graduated external pressure to the leg, highest at the ankle and decreasing upward, so that fluid gets pushed back toward the body. For venous insufficiency and lymphedema, that is the core of treatment.

On a leg where arterial inflow is already reduced, the same external pressure works against blood trying to get in. The result can be tissue that was barely coping, and then is not, which is how a leg with no wound develops one. That is the whole reason compression carries contraindications at all, and we walked through the full list in Who Should Not Wear Compression Socks.

Here is how the ABI is commonly mapped to compression planning in general clinical practice. These bands are a widely used convention, not a fixed rule, and the prescribing clinician decides what is right for a given patient and a given leg.

This is why an MCB DME fitting sometimes starts with a phone call to your physician's office rather than a tape measure. We would rather wait two days for a number than fit a garment that causes a problem. Once the arterial question is settled, our measuring guide covers what the fitting itself looks like.

Getting the test in North Jersey and Rockland

You do not schedule an ABI directly with a DME supplier. It is ordered and performed by a clinical practice. Across northern New Jersey and Rockland County, that is usually one of:

• Primary care, often as part of a diabetes or cardiovascular check
• Vascular surgery, where a full lower-extremity arterial study with segmental pressures may be done instead
• Podiatry, particularly for diabetic foot care
• Wound care centers, before deciding on a compression plan for a leg ulcer
• Cardiology, alongside other vascular risk assessment

Coverage for the test itself depends on your plan and on why it is being done. The practice performing it is the right place to ask.

For referring providers

If you are sending a patient to MCB DME for compression, the fastest path is an order that already answers the arterial question. What helps most:

• The ABI value for the limb being treated, with the date it was performed, or a note that a TBI or duplex was done instead and why
• The diagnosis and ICD-10 code driving the compression need
• The compression class in mmHg, or a note that you would like our fitter to recommend one
• Any relevant contraindications: decompensated heart failure, active infection on the limb, known severe arterial disease
• Whether this is a first fitting or a replacement

That single line with the ABI value saves the most back-and-forth of anything on the list. Our provider page has current contact and fax details, and we cover the arterial side of our service in Arterial Compression Therapy for PAD.

Frequently asked questions

Does an ABI test hurt?

No. It feels like having your blood pressure taken, twice on each limb. The Doppler gel is cool. There are no needles and nothing is injected.

How long does it take?

The cuff measurements typically take 10 to 20 minutes, plus a period of lying flat and resting beforehand. An exercise ABI with a treadmill component takes longer.

Can I do an ABI at home?

Not reliably. Home blood pressure cuffs are not designed for ankle placement and do not include a Doppler, so the reading is not comparable to a clinical ABI. Consumer devices marketed for this are not a substitute for a clinician-performed test.

What if my ABI is normal but my legs still hurt when I walk?

Ask about an exercise ABI. Some people have arteries that perform adequately at rest and inadequately under demand. It is also worth ruling out spinal stenosis and arthritis, both of which cause walking pain through entirely different mechanisms. Our post on the signs of poor circulation covers how those patterns differ.

Why did my doctor test my toe instead of my ankle?

Almost certainly because your ankle arteries were too stiff to compress, which happens commonly in diabetes and kidney disease. The toe pressure is the more reliable measurement in that situation, not a lesser one.

How often should an ABI be repeated?

There is no single answer. It depends on your symptoms, your risk factors, and whether anything has changed. If your walking distance has shortened, a wound has appeared, or you are about to start compression on a leg that has not been assessed recently, that is a reason to ask.

Does MCB DME perform ABI testing?

No. We are a DMEPOS supplier, not a diagnostic facility. We coordinate with your physician's office to obtain the result, and we can tell you what to ask for.

Key takeaways

• The ABI is ankle systolic pressure divided by arm systolic pressure, done on each leg separately.
• 0.90 or below is consistent with PAD. 0.91 to 0.99 is borderline. 1.00 to 1.40 is normal. Above 1.40 means the reading is unreliable and a toe pressure is needed instead.
• Diabetes and kidney disease can produce falsely high ABI values, which is worth knowing before accepting a reassuring number.
• The test is quick, needle-free, and ordered by a clinical practice rather than by a DME supplier.
• The ABI is what makes a compression plan safe. It is the reason a fitting sometimes waits on a phone call to your doctor.

Next steps

MCB DME is a Medicare-enrolled DMEPOS supplier in Hawthorne, NJ. We serve patients across northern New Jersey and New York, including Rockland County. We fit compression garments, supply arterial and lymphedema pumps, and coordinate with your physician when arterial status needs to be confirmed first.

If you have an ABI result and are not sure what it means for compression, bring us the number and we will walk through it with you. See our compression therapy options, learn about the arterial pump program, or call (973) 553-0777. You can also reach the team here, or ask Lumi, our 24/7 chatbot, at the bottom right of any page.

This article is for general education and is not medical advice. Testing and treatment decisions belong to you and your physician.