The normal ankle-brachial index (ABI) range for most adults is 1.00 to 1.40. The test compares blood pressure at the ankle with blood pressure in the arm to assess blood flow to the legs. A result of 0.91 to 0.99 is considered borderline, while 0.90 or lower is abnormal. A result above 1.40 may mean the ankle arteries are stiff and need further assessment.
What Is Considered a Normal Ankle-Brachial Index?
A normal resting ankle-brachial index (ABI) is between 1.00 and 1.40. This range generally suggests that blood is flowing adequately through the arteries in the legs. Healthcare professionals use the ABI to help assess for peripheral artery disease (PAD), a condition in which narrowed arteries reduce blood flow to the limbs.
The 2024 American College of Cardiology and American Heart Association guideline defines four main categories for resting ABI results. These categories help clinicians describe findings consistently and determine whether further testing may be appropriate.
| ABI value | Classification | What it may mean |
|---|---|---|
| 1.00–1.40 | Normal | Generally suggests adequate blood flow to the legs. |
| 0.91–0.99 | Borderline | May indicate an early or uncertain reduction in arterial blood flow. |
| 0.90 or lower | Abnormal | Suggests reduced blood flow that may be associated with peripheral artery disease. |
| Above 1.40 | Noncompressible | May indicate arteries that are too stiff to compress adequately for a reliable measurement. |
These categories apply to resting ABI measurements. The number is interpreted alongside symptoms, medical history, physical examination findings, and, when needed, additional vascular tests.
What Does the Ankle-Brachial Index Measure?
The ankle-brachial index compares the systolic blood pressure at the ankle with the systolic blood pressure in the arm. Systolic pressure is the pressure in the arteries when the heart contracts and pumps blood.
In a typical ABI assessment, a healthcare professional measures blood pressure at both ankles and both arms. A blood pressure cuff and a handheld Doppler ultrasound device help detect blood flow in the arteries. The measurements are then used to calculate a separate ABI value for the right and left legs.
According to Mayo Clinic, the ABI is a quick, noninvasive test used to check for peripheral artery disease. It usually requires lying on your back while the measurements are taken and generally takes only a few minutes.
How Is the ABI Calculated?
The ABI is calculated by dividing the selected systolic blood pressure measurement at the ankle by the higher systolic blood pressure measured in either arm. For each leg, the healthcare professional generally uses the higher pressure measured in the two ankle arteries.
For example, if the selected ankle pressure is 120 mmHg and the higher arm pressure is 120 mmHg, the ABI is 1.00. If the ankle pressure is 96 mmHg and the arm pressure is 120 mmHg, the ABI is 0.80. The second result falls below the normal range and would generally prompt clinical assessment for reduced blood flow.
What Do Low, Borderline, and High ABI Results Mean?
ABI of 1.00 to 1.40: Normal range
A result within this range generally indicates that blood pressure at the ankle is appropriate in relation to blood pressure in the arm. It makes significant peripheral arterial obstruction less likely, although it does not rule out every circulation problem.
If a person continues to experience leg discomfort during walking or other symptoms that raise concern about reduced circulation, a healthcare professional may recommend additional assessment despite a normal resting ABI.
ABI of 0.91 to 0.99: Borderline range
A borderline result falls just below the normal range. It may reflect a mild reduction in blood flow or an early arterial abnormality, but the result alone does not establish the cause of any symptoms.
Further evaluation depends on the person's clinical history and examination. When symptoms suggest peripheral artery disease despite a borderline resting result, an exercise ABI test may help identify changes in blood flow that become apparent during physical activity.
ABI of 0.90 or lower: Abnormal range
An ABI of 0.90 or lower is considered abnormal and suggests that blood pressure at the ankle is lower than expected compared with the arm. This finding is associated with peripheral artery disease, in which narrowed or blocked arteries limit blood flow to the legs.
The degree of reduction can provide useful information, but it should not be used alone to determine the severity of a person's symptoms or the treatment they need. A clinician may consider further testing, including vascular ultrasound, to understand the location and extent of an arterial problem.
The Merck Manual Professional Edition explains that a low ABI is an important finding when assessing for peripheral artery disease. The result is considered together with the clinical picture and other relevant test findings.
ABI above 1.40: Noncompressible arteries
A result above 1.40 is not considered normal. It may occur when the arteries in the ankle have become stiff and cannot be compressed normally by a blood pressure cuff. Arterial calcification, in which calcium builds up in the vessel walls, can contribute to this problem.
These measurements can be particularly difficult to interpret in people with long-standing diabetes or advanced chronic kidney disease. A healthcare professional may recommend a toe-brachial index (TBI), which compares blood pressure in the big toe with blood pressure in the arm. Toe arteries may provide more useful measurements when ankle arteries are difficult to compress.
Can a Normal ABI Rule Out Peripheral Artery Disease?
A normal resting ABI makes significant arterial narrowing less likely, but it does not exclude peripheral artery disease in every situation. Some people experience leg pain or cramping during walking even when their resting ABI falls within the normal range.
The American Heart Association notes that diagnosing peripheral artery disease involves a person's medical history, physical examination, and appropriate tests. If symptoms remain concerning despite a normal or borderline resting ABI, a clinician may recommend an exercise ABI test or other vascular investigations.
An exercise ABI test measures blood pressure at the ankle before and after activity, often walking on a treadmill. Comparing the results can help clinicians identify an abnormal change in blood flow that may not be evident while a person is resting.
When Should You Discuss an ABI Result With a Healthcare Professional?
Discuss the findings with the healthcare professional who ordered the test, particularly if the value is below 1.00 or above 1.40. The appropriate next step depends on the result, symptoms, medical history, and whether the test measurements were reliable.
Evaluation is especially important when leg pain repeatedly occurs during walking, wounds on the feet or lower legs heal slowly, or symptoms are persistent or worsening. Sudden severe pain in a leg or foot, especially with new coldness, pallor, numbness, or weakness, requires urgent medical assessment rather than waiting for a routine ABI review.
The National Heart, Lung, and Blood Institute explains that healthcare professionals use the ABI alongside medical history, physical examination, and other diagnostic tests to assess peripheral artery disease. Depending on the findings, additional tests may help evaluate blood flow more completely.
Key Points About the Normal ABI Range
For most adults, a normal resting ankle-brachial index is 1.00 to 1.40. Values of 0.91 to 0.99 are borderline, values of 0.90 or lower are abnormal, and values above 1.40 suggest noncompressible arteries. These ranges provide a standard way to describe test results, but they do not replace clinical interpretation. Symptoms, examination findings, and other vascular tests may influence what a particular result means and whether follow-up is needed.