Which Arm Should You Use to Measure Blood Pressure?

Use the arm that gives the higher reading. The first time you measure, check both arms. If one reads consistently higher, use that arm for all future readings. For most people the difference between arms is small, but a large, consistent gap is worth mentioning to your doctor.

The arm you pick can change your numbers, and using the same one each time is part of getting readings you can trust. Here is what the guidelines say and how to put it into practice at home.

Does it matter which arm you use for blood pressure?

Yes, a little. It is normal for the reading in one arm to differ slightly from the other. When it comes to which arm for blood pressure measurement, the American Heart Association (AHA) advises checking both arms the first time, then using the arm with the higher reading for ongoing measurements. That way you avoid quietly underestimating your numbers by using the lower arm. The UK’s NHS gives similar guidance: readings can vary between arms, so it helps to know which one runs higher for you.

How to find your reference arm

You only need to do this once.

1. Sit quietly for about five minutes, feet flat on the floor, back supported.
2. Take a reading on your left arm, resting it at heart level.
3. Wait a minute, then take a reading on your right arm the same way.
4. Repeat once more on each arm and compare the averages.

Whichever arm reads higher becomes your reference arm. From then on, measure that arm each time so your day to day numbers stay comparable. If the two arms are very close, either is fine, just be consistent.

What a difference between your arms means

A small gap between arms is common and usually nothing to worry about. It becomes more meaningful when the difference is larger and shows up consistently.

According to an AHA scientific statement on blood pressure measurement, a repeated difference of 10 mmHg or more in the systolic (top) number can be linked with higher cardiovascular risk, and 15 mmHg or more is more strongly associated with underlying blood vessel disease. A single odd reading is not a diagnosis, but a pattern of large gaps is a reason to check in with your doctor.

Getting an accurate reading, whichever arm you use

The arm you choose matters less than measuring it well. Rest the arm on a table so the cuff sits level with your heart, keep your feet flat, and stay quiet without talking during the reading. Use a bare arm rather than measuring over clothing. For the full walkthrough, see our guide on how to measure blood pressure at home, and avoid the usual pitfalls with 7 mistakes that ruin your home reading. Timing helps too: measure at the best time of day and consider taking two readings and averaging them.

When to see a doctor

Home tracking is helpful, but a few situations call for professional advice:

• Seek emergency care for a reading higher than 180/120 mmHg together with chest pain, shortness of breath, weakness or numbness, vision changes, trouble speaking, or a severe headache.
• Speak to your doctor if you notice a consistent difference of about 10 to 15 mmHg or more between your arms, since this is worth checking.
• Check in if your readings are regularly 130/80 mmHg or above, or are climbing over time.

This guide is general information and does not replace personalised medical advice.

Frequently asked questions

Is blood pressure higher in the left or right arm? It varies from person to person. Neither arm is automatically higher, which is exactly why you measure both once and then stick with whichever runs higher for you.

Should I always use the same arm? Yes. Once you know your reference arm, use it every time so your readings stay comparable and any real changes are easy to spot.

Why is my blood pressure so different in each arm? A small difference is normal. A large, repeated gap can reflect differences in the blood vessels and is worth raising with your doctor, especially if it is 10 mmHg or more in the top number.

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Medically reviewed by: _________________ (clinician name and credential to be added)

Last reviewed: July 2026

Sources: American Heart Association (Measurement of Blood Pressure in Humans, Scientific Statement; Monitoring Your Blood Pressure at Home); UK National Health Service (NHS, How to check your blood pressure).

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