Blood pressure different in each arm

It is common to get a slightly different reading in your left and right arm. A small difference is usually nothing to worry about. A large one that keeps coming back is worth telling your doctor about.

Is a difference between arms normal?

Yes, a small one. The American Heart Association says you can use either arm for home readings, and that there usually isn't a big difference between them. Part of what you see is also ordinary variation: two readings on the same arm a minute apart are rarely identical either.

How big a difference matters?

Guidelines and studies look at the difference in the top number (systolic):

• The UK's NICE guideline says that when hypertension is being diagnosed, blood pressure should be measured in both arms. If the difference is more than 15 mmHg, the readings are repeated, and if it is still more than 15 mmHg, later readings are taken on the arm with the higher reading.
• A 2020 analysis of 24 studies with more than 53,000 people, published in the journal Hypertension, proposed 10 mmHg as the upper limit of normal, because a difference that large was linked with a higher risk of heart and circulation problems.

Those numbers come from readings taken carefully by health care professionals. At home, a one-off difference can easily come from how the cuff was fitted, posture, or moving or talking during the reading. Repeat the readings before drawing any conclusion.

How to compare your arms at home

1. Get ready as you would for any reading: no caffeine, smoking or exercise for 30 minutes, then sit quietly for 5 minutes.
2. Take a reading on one arm, then on the other, with the cuff on bare skin and each arm supported at heart level. Use the right cuff size for each arm.
3. Repeat once or twice, and write down every reading with the arm you used.
4. If one arm is clearly and repeatedly higher, show your log to your doctor.

Which arm should I use for my home readings?

If there's no meaningful difference, either arm is fine; just use the same one each time so your readings can be compared. If your doctor has found that one arm reads higher, they will usually ask you to use that arm. Always note the arm in your log.

When to tell your doctor

Mention it at your next appointment if one arm is repeatedly higher by around 10 to 15 mmHg or more. Your doctor can repeat the readings properly and decide whether anything else needs to be checked. Contact them sooner, or call your local emergency number, if you have symptoms such as chest pain, shortness of breath, numbness, weakness, vision changes or difficulty speaking.

Record the arm with every reading

Our free printable blood pressure logs have a notes column for the arm. In the BP Notebook app you can tag each reading with the arm (left or right) and your position, so your history shows which arm each reading came from.

Sources

• American Heart Association. Monitoring your blood pressure at home. Last reviewed August 14, 2025.
• National Institute for Health and Care Excellence (NICE). Hypertension in adults: diagnosis and management (NG136), recommendation 1.2.1.
• Clark CE, et al. Associations between systolic interarm differences in blood pressure and cardiovascular disease outcomes and mortality: individual participant data meta-analysis. Hypertension, 2021; 77(2): 650–661.

Updated November 3, 2026