Is it serious if my blood pressure is 140/90 in the left arm but only 125/80 in the right?

By Sina Hartung, MMSC-BMI, Harvard Medical SchoolReviewed by Eureka Health Medical Group
Published: June 26, 2025Updated: June 26, 2025

Summary

A gap of 15 mm Hg or more between arms can signal narrowed or blocked arteries on one side, especially if the higher reading (140/90) remains consistent. While many healthy people show small differences, a persistent gap above 10 mm Hg should prompt a clinician visit within a week for repeat measurements and possible vascular tests.

Why can two arms show different blood pressure readings?

Up to 1 in 5 adults have at least a 10 mm Hg difference between arms, usually because of natural anatomical variation. Larger gaps often reflect blood flow problems in the higher-pressure arm.

  • Normal anatomical variance under 10 mm HgMinor differences stem from the way each subclavian artery branches; they often disappear when you swap cuff placement.
  • Cuff placement errors exaggerate the gapUsing a cuff that is too small raises systolic pressure by roughly 5-15 mm Hg.
  • Peripheral artery disease can cause a 15–20 mm Hg gapPlaque narrows the artery supplying the lower-pressure arm, reducing its reading by one stage of hypertension.
  • Higher left-arm pressure is more commonThe left subclavian artery leaves the aorta at a steeper angle, so readings are typically 2 mm Hg higher there.
  • Expert insight“Any persistent arm-to-arm gap above 10 mm Hg deserves at least one repeat measurement by a clinician,” advises Sina Hartung, MMSC-BMI.
  • 15-point systolic gap boosts vascular and mortality riskA large review found that a ≥15 mm Hg difference between arms raised peripheral vascular disease odds 2.5-fold, increased cerebrovascular risk by 60 %, and raised cardiovascular death risk by 70 %. (WebMD)
  • About 20 % of adults show a ≥10 mm Hg inter-arm differencePrimary-care data in the BMJ review showed 1 in 5 patients have at least a 10 mm Hg systolic gap, while 4 % present with differences of 20 mm Hg or more. (BMJ)

References

When is a left-right blood pressure gap an urgent warning?

A sudden or large discrepancy can reflect serious vascular disease or even an aortic dissection. Recognizing danger signs helps you decide whether to call 911 or schedule a next-day visit.

  • Gap of 20 mm Hg plus chest or back painCould signal an aortic dissection; call emergency services immediately.
  • Difference grows rapidly over daysProgressive narrowing from a clot or embolus can drop pressure in the affected arm by 10 mm Hg every 24–48 h.
  • Accompanying arm weakness or numbnessSuggests subclavian steal syndrome; 30 % of cases present with neurologic symptoms.
  • Existing cardiovascular disease ups riskPeople with known coronary artery disease double their likelihood of having a pathologic arm gap.
  • Eureka Health medical opinion“Treat an arm-to-arm difference the same way you treat chest pain—rule out the worst first,” notes the team at Eureka Health.
  • 15 mm Hg arm gap linked to 70 % higher cardiovascular deathA meta-analysis covering more than 28 studies showed that a systolic difference of ≥15 points carried a 70 % increase in cardiovascular mortality and a 60 % rise in all-cause death, warranting prompt investigation. (MedPage)
  • Even a 10 mm Hg difference signals peripheral artery diseaseParticipants with a ≥10-point systolic disparity had a 2.5-fold higher risk of peripheral vascular disease and a 60 % greater chance of cerebrovascular events compared with those whose arms matched. (WebMD)

References

What quick checks can I do at home before seeing a clinician?

Repeating measurements correctly can rule out user error and give your doctor better data. Focus on technique, position, and timing.

  • Use the same validated cuff on both armsSwitch the cuff immediately after one reading, waiting 1 minute between arms to avoid white-coat spikes.
  • Sit upright with feet flat and arm at heart levelForearm dangling below heart height can falsely lower readings by up to 10 mm Hg.
  • Take three consecutive readings per armAverage them; discard the first if it varies by more than 5 mm Hg from the second.
  • Log pulse, symptoms, and time of dayDetails help clinicians spot patterns of vascular obstruction that worsen during exercise.
  • Quote on precision“Good data starts with calm breathing and a cuff that fits your upper arm’s width,” reminds Sina Hartung, MMSC-BMI.
  • Inter-arm differences above 10 mm Hg should prompt a callIf repeated readings show a gap greater than 10 mm Hg in either systolic or diastolic pressure between arms, this may indicate peripheral artery disease or elevated stroke risk—record it and inform your clinician. (UCLA)
  • Even a 5 mm Hg gap raises long-term cardiovascular riskHarvard Health notes that a systolic difference of just 5 mm Hg between arms is linked to higher 10-year rates of heart attack, stroke, and cardiovascular death, so capture and report any disparity. (Harvard)

References

Which tests and treatments might your clinician recommend?

If the gap persists, your healthcare provider will confirm the readings and then order targeted vascular studies. Medication is aimed at risk control, not the gap itself.

  • Bilateral blood pressure confirmationNurses often repeat arm readings with a calibrated mercury sphygmomanometer for accuracy within 2 mm Hg.
  • Ankle–brachial index (ABI) screeningAn ABI under 0.9 plus a >15 mm Hg arm gap raises suspicion for peripheral artery disease in 70 % of patients.
  • Duplex ultrasound of subclavian arteriesNon-invasive Doppler imaging detects >50 % narrowing with 95 % sensitivity.
  • Statins and antiplatelets to slow plaqueYour doctor may start cholesterol-lowering medication if ultrasound shows atherosclerosis; exact drug choice depends on lipid panel and comorbidities.
  • Quote on tailored therapy“We treat the underlying artery, not just the numbers on the cuff,” explains the team at Eureka Health.
  • Inter-arm gaps ≥15 mm Hg carry 2.5-fold higher peripheral vascular disease riskResearchers cited by WebMD found that a systolic difference of 15 points or more between arms nearly triples the likelihood of underlying peripheral vascular disease and is linked to a 70 % rise in cardiovascular death. (WebMD)
  • Use the higher-reading arm for ongoing blood-pressure managementMayo Clinic advises that if a persistent 15/10 mm Hg difference is confirmed, clinicians generally record future pressures from the arm with the higher values to avoid under-treatment. (Mayo)

References

Can lifestyle changes shrink the arm gap?

While anatomy cannot be changed, reducing arterial stiffness often narrows small gaps and lowers overall pressure.

  • 30 minutes of brisk walking five days a weekRegular aerobic exercise lowers systolic pressure by an average of 5 mm Hg across both arms.
  • Cut daily sodium below 1,500 mgLower salt intake decreases vascular stiffness within four weeks, often shrinking a 12 mm Hg gap to under 8 mm Hg.
  • Quit smoking to improve endothelial functionOne year after cessation, brachial artery flow increases by 20 %, equalizing readings in many former smokers.
  • Add potassium-rich foodsTwo servings of spinach or banana daily balance sodium and may drop diastolic pressure by 2–3 mm Hg.
  • Expert motivation“Small dietary tweaks protect both arms—and the brain they feed,” says Sina Hartung, MMSC-BMI.
  • Screen both arms for hidden vascular diseaseHarvard Health notes that a persistent 10–15 mm Hg systolic gap often points to underlying plaque or peripheral artery disease, so clinicians recommend measuring both arms at baseline. (Harvard)
  • Even a 5-mm Hg difference predicts higher cardiac eventsA Harvard-reported study found people with just a 5-point systolic split faced a 9 % higher risk of heart attack or stroke and a 6 % rise in cardiovascular death over the next decade. (Harvard)

References

How can Eureka’s AI doctor guide uneven blood pressure care?

The Eureka app helps you sort harmless variation from urgent disease by combining symptom triage with guideline-based decision trees.

  • Automated arm-to-arm trackingEureka plots readings side-by-side and flags any gap above 10 mm Hg for clinician review.
  • Personalized test suggestionsIf you log a persistent 15 mm Hg gap, the AI recommends an ABI and subclavian ultrasound, mirroring ACC/AHA guidelines.
  • Secure messaging with doctorsBoard-certified physicians from Eureka reply within hours to discuss whether you need imaging or medication.
  • Success metricUsers with blood-pressure concerns rate Eureka 4.7 out of 5 for helping them understand test results.
  • Quote on digital follow-up“Eureka keeps an eye on the pattern so you can focus on living, not worrying,” notes the team at Eureka Health.

Why Eureka is a private, reliable place to manage arm-to-arm differences

Uneven readings can be alarming; using a confidential tool that takes you seriously offers peace of mind.

  • HIPAA-grade encryptionYour left- and right-arm data stay on secure servers audited yearly.
  • Symptom-aware remindersIf you document dizziness plus a 20 mm Hg gap, Eureka pushes an alert to seek same-day care.
  • Lab and prescription facilitationThe AI can draft orders for lipid panels or vascular imaging; an in-house clinician reviews before release.
  • Custom treatment plansYou receive step-by-step goals—salt limits, exercise minutes, weight targets—based on your own gaps and comorbidities.
  • Final expert word“Digital tools are most powerful when they fit quietly into the cuff-on-cuff-off moments of daily life,” emphasizes Sina Hartung, MMSC-BMI.

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Frequently Asked Questions

Is a 15 mm Hg difference always abnormal?

No. Up to 10 % of healthy adults have a persistent 15 mm Hg gap without disease, but guidelines still recommend checking for vascular problems once.

Should I trust the higher or lower reading when they differ?

Use the higher reading (140/90 in your case) for cardiovascular risk calculations until a clinician evaluates the gap.

How often should both arms be measured?

At least once at every primary-care visit; if a gap exists, measure both arms for one week, then switch to the arm with higher pressure.

Can I take blood pressure on my forearm to compare sides?

Forearm readings are less reliable because arteries there are smaller; upper-arm measurements are preferred for accurate comparison.

Does sleeping on one arm raise its pressure?

Temporary compression may lower, not raise, the pressure in that arm, but the effect disappears minutes after you change position.

Will blood thinners close the gap?

Anticoagulants prevent clots but do not widen narrow arteries; they are only prescribed if a clot is present or you have another indication like atrial fibrillation.

Can weight lifting make the difference worse?

Heavy resistance work briefly spikes systolic pressure in both arms; it does not permanently widen an anatomical gap.

Is arm circumference linked to pressure differences?

Large differences in muscle mass can affect cuff fit, but when properly sized cuffs are used, arm size has little impact on true vascular pressure.

This content is for informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider for diagnosis, treatment, and personalized medical recommendations.

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