With high blood pressure, caffeine spikes it; 2 weeks of coffee didn't
In people with high blood pressure, 200 to 300 mg of caffeine raised it for three hours or more. Over about 2 weeks, coffee raised it no more than going without caffeine.
What the study found
A caffeine dose raised high blood pressure; 2 weeks of coffee did not
With high blood pressure, 200 to 300 mg of caffeine raised it 8.1 mmHg systolic and 5.7 diastolic within an hour, for three hours or more. Over about 2 weeks, coffee raised it no more than going without caffeine, and seven long-term studies tied coffee to no extra cardiovascular disease.
The caveat · Test doses, not a morning cup
The hour-by-hour rise comes from single doses given in short test sessions, which may not match a regular drinker's morning cup. Only three trials, of about 2 weeks each, looked past the first day, too short to catch a change that builds more slowly. An older review found the rise strongest in people who already have high blood pressure, so it may be smaller in others.