CBD reduces blood pressure after 2.5 weeks of use

In this randomized, placebo-controlled, crossover study, the goal was to determine the effects of oral CBD on high blood pressure (hypertension) over a 5 week period. It was published in the journal Cannabis & Cannabinoid Research in April 2023.

It included 70 patients with mild or moderate primary hypertension, who were "randomly assigned to receive either 5 weeks of oral CBD or placebo-matched controls". 

It took an average of 2.5 weeks of daily use to show improvements which is consistent with some patient anecdotes that CBD effects can take several weeks of daily use to be most effective (for other conditions, especially pain).

They also observed that once an effective CBD dose was found, increasing that dose (uptitration) did NOT show increasing benefits. The 'statistically significant' range of REDUCTION in blood pressure varied among patients:

• mean (1.01 to 5.44 mmHg)
• systolic (1.72 to 7.42 mmHg)
• diastolic (0.30 to 6.01)

Unfortunately, the full text study is behind a paywall, so we don't know much about the most effective dosages.

The results in the authors' words:

Administration of CBD reduced average 24 h mean, systolic, and diastolic BP after 2.5 weeks

these values largely remained stable following the uptitration of CBD dosing

There were no changes in liver enzymes or serious adverse events

Author conclusions:

chronic administration of CBD reduces ambulatory BP in those with untreated and treated hypertension

lack of serious AEs [adverse events, or side effects] implies safety and tolerability of the above-noted CBD formulation.

The abstract is here at PubMed.