What Is an ABI Test and How Is It Performed?

The Ankle-Brachial Index (ABI) test is a simple, painless way to check how well blood is flowing in your legs. It works by comparing the blood pressure in your ankles with the blood pressure in your arms. If the pressure in your legs is much lower than in your arms, it may be a sign of peripheral artery disease (PAD), a condition where narrowed or blocked arteries reduce circulation to the legs.

Doctors often order an ABI test if you have leg pain when walking, wounds on your feet or legs that are slow to heal, or risk factors such as smoking, diabetes, high cholesterol, high blood pressure, or a family history of vascular disease. Symptoms like cramping, numbness, or cold feet may also point toward PAD, making the ABI an important first step in diagnosis.

The test itself is quick and non-invasive, usually taking just 10–15 minutes in a doctor’s office or vascular lab. While you lie flat, a technician places blood pressure cuffs on both arms and ankles. Using a Doppler ultrasound device, they measure your blood flow and record the pressures. By dividing the ankle pressure by the arm pressure, your ABI number is calculated. A normal ABI is between 1.0 and 1.3, meaning blood flow to your legs is healthy. A borderline result falls between 0.91 and 0.99, while anything below 0.90 suggests PAD. Severe disease may show a reading of 0.40 or lower, indicating a higher risk of serious complications like ulcers or tissue damage.

The ABI test is completely safe — no needles, no dye, and no radiation — and feels just like having your blood pressure checked on your arm, only on your ankles too. Results are available right away, making it a fast and reliable way to identify circulation problems early.