Blood Pressure Differs Between Arms: Which Arm Should You Use?

Short answer: One pair of different readings does not diagnose vascular disease. Repeat both arms under the same conditions. If one arm remains consistently higher, that is usually the arm to use for ongoing home readings, and the difference itself should be shown to a clinician. NICE advises repeating a systolic difference greater than 15 mmHg and, if it remains greater than 15 mmHg, using the higher-reading arm for future measurements. Korean hypertension guidance likewise recommends measuring both arms at the first assessment and using the higher arm afterward.

Who is this for?

This general guide is for adults who get different right- and left-arm readings with a validated upper-arm monitor or during a clinic visit. It is particularly useful at an initial hypertension assessment, when starting a new monitor, or when a difference appears after years of measuring only one arm.

If you have a dialysis fistula, lymphedema risk after breast or underarm surgery, an injured or paralyzed arm, or a cast, ask your care team which arm is safe to use instead of repeatedly compressing both arms.

Why can a single pair differ?

Blood pressure varies from minute to minute. Anxiety during the first reading, talking, arm position, an incorrect cuff size and the order of measurements can create a difference. Research suggests that sequential measurement can overestimate inter-arm differences compared with simultaneous measurement. A single reading from one arm immediately after rest and another several minutes later is therefore not a reliable comparison.

How can you recheck at home?

  1. Sit quietly for about five minutes with your back supported and feet on the floor.
  2. Use a cuff that fits your bare upper arm and support the arm at heart level.
  3. Measure both arms initially. When repeating, change which arm is measured first rather than always starting on the same side.
  4. Record the date, time, arm, systolic and diastolic values, pulse and measurement order.
  5. If the same arm is repeatedly higher, use that arm for routine tracking and show both-arm records at the next visit.

Do not average the two arms together before deciding on a reference arm, and do not select only the lower arm. Medication changes and personal blood-pressure targets should not be based on one day of inter-arm readings.

How large a difference needs review?

Thresholds vary somewhat by guideline and measurement method. NICE uses a repeated systolic difference greater than 15 mmHg as the point for continuing with the higher-reading arm. Small differences are common, but individual-participant meta-analyses indicate that larger persistent differences can carry cardiovascular risk information.

If a difference persists across several carefully measured sessions or is newly much larger than before, bring the log and monitor to a clinical visit. A clinician can repeat the measurements and decide whether vascular risk assessment is appropriate. Inter-arm difference alone cannot diagnose a blocked artery or aortic disease.

When is it an emergency?

Do not spend time repeating measurements if the difference appears with sudden severe chest or upper-back pain, collapse, new speech difficulty or one-sided weakness, sudden vision change, or an arm that becomes acutely cold, pale, very painful, numb or weak. Use emergency services now. In Korea call 119; elsewhere call your local emergency number. These combinations can rarely occur with emergencies such as aortic dissection, stroke or acute loss of blood flow.

Questions to ask at a visit

  • Which arm should I use for future home readings?
  • Could cuff size or technique explain the difference?
  • Should both arms be repeated in the clinic or measured simultaneously?
  • Does this pattern warrant assessment for peripheral artery disease or other vascular risk?
  • Which readings should be used for my personal target and medication review?

Related resources

Sources and review date

Reviewed: October 7, 2026

This is general health information, not personal diagnosis or medication advice. Interpretation can differ with symptoms, conditions and measurement technique.