Aspirin Does Not Significantly Raise Blood Pressure
Based on the highest quality and most recent evidence, aspirin does not cause clinically meaningful increases in blood pressure in most patients. The most robust data from a 2024 randomized controlled trial of over 19,000 older adults showed no significant effect of daily low-dose aspirin on blood pressure 1, and a 2024 meta-analysis of 20,312 patients confirmed these findings 2.
Key Evidence Summary
Most Recent High-Quality Data
The ASPREE trial (2024) - the largest and most recent randomized controlled study - found that 100 mg daily aspirin produced:
- No significant change in systolic BP: difference of only -0.03 mm Hg (95% CI: -0.13,0.07) 1
- No significant change in diastolic BP: difference of only -0.05 mm Hg (95% CI: -0.11,0.01) 1
- No difference in rates of new hypertension between aspirin and placebo groups 1
These findings remained consistent across all subgroups including:
- Patients already on antihypertensive medications
- Those with diabetes or chronic kidney disease
- Different age groups and frailty levels 1
Supporting Meta-Analysis
A 2024 systematic review and meta-analysis corroborated these findings, showing aspirin had no effect on either systolic (MD = -0.78 mm Hg) or diastolic blood pressure (MD = -0.86 mm Hg) 2.
Important Caveats and Nuances
Timing-Dependent Effects (Conflicting Evidence)
Some older, smaller studies (2005-2006) suggested that aspirin's effect on blood pressure may depend on when it is taken:
- Morning dosing: May slightly increase BP by 1.5-2.6 mm Hg 3, 4
- Bedtime dosing: May decrease BP by 5.5-11 mm Hg, particularly in "non-dipper" hypertensive patients 3, 4
However, these studies were uncontrolled, unmasked, and potentially biased 5. The more rigorous 2024 ASPREE trial, which did not specify timing, found no overall effect 1.
Historical Context
Very old data (1981,1984) suggested high-dose aspirin (1.5 g/day) might transiently increase blood pressure 6, but this is not relevant to modern low-dose aspirin therapy (75-100 mg/day used for cardiovascular prevention).
NSAIDs vs. Aspirin
Critical distinction: While other NSAIDs are known to increase blood pressure and interfere with antihypertensive medications 7, low-dose aspirin appears to behave differently and does not share this effect to a clinically significant degree 8, 2, 1.
Clinical Implications
For patients with hypertension considering aspirin for primary prevention:
- Blood pressure elevation is not a contraindication to low-dose aspirin use
- No special blood pressure monitoring is required solely due to aspirin initiation
- Focus counseling on actual aspirin risks: gastrointestinal bleeding (2-4 per 1000 over 5 years) and hemorrhagic stroke (0-2 per 1000 over 5 years) 9
The decision to use aspirin should be based on: