When using cannabidiol (CBD), blood pressure and other problems associated with cardiovascular health could one day officially be a thing of the past. This might take a while, though. The available data are promising, warranting further investigation, but much more clinical research is necessary before CBD can be prescribed for blood pressure issues.
Let's take a look at what science says on this topic, as well as other established CBD benefits.
Never attempt to take high-dose CBD or replace your current blood pressure medicine with CBD without the consent of your prescribing physician.
Thus far, unfortunately, there’s a great lack of conclusive clinical data regarding CBD's effect on high blood pressure. Here, we take a look at a review and a small study to gain answers.
Preclinical data, reviewed in 2013, suggest that this cannabinoid affects the bloodwork of anesthetized rats—temporarily.
"One study has shown that in pentobarbitone anaesthetized rats, CBD (50 µg kg−1 i.v. but not 10 µg kg−1) causes a significant but transient 16 mmHg fall in mean arterial blood pressure without affecting heart rate."
The researchers go on to note that no other studies report any acute effects of in vivo treatment with CBD on baseline heart rate or blood pressure in animal studies, though. Also, CBD treatment in human subjects did not result in changes in resting blood pressure or heart rate.
They, therefore, say that "...the majority of evidence suggests there is no effect of CBD on haemodynamics."
For this, the authors offer a few possible explanations, not summarily ditching the notion that through treatment with CBD, blood pressure could be alleviated.
They say that:
"The potential ability of CBD treatment in humans to reduce the cardiovascular (as well as behavioral) response to stress could have significant effects on the development of atherosclerosis and hypertension, which are known to be accelerated by stress."
The same review listed other benefits of CBD on the cardiovascular system, including cardioprotection, vasculoprotection, and neuroprotection against ischemic strokes as well as blood cell activity.
"...these studies show that CBD influences both the survival and death of white blood cells, white blood cell migration and platelet aggregation, which could underpin the ability of CBD to delay or prevent the development of cardiovascular disorders." 
In a more recent randomized, placebo-controlled, double-blind, crossover study, the following was concluded:
"This data shows that acute administration of CBD reduces resting [blood pressure - BP] and the BP increase to stress in humans, associated with increased [heart rate] HR. These hemodynamic changes should be considered for people taking CBD. Further research is required to establish whether CBD has a role in the treatment of cardiovascular disorders." 
In this small but well-designed study, the participants were subjected to mental and physical stresses that included mental arithmetic, isometric exercise, and the cold pressor test. (The latter is designed to clinically evaluate autonomic and left ventricular function, and it is performed by pressing a subject's hand into ice-cold water for approximately a minute.) 
The researchers found, in post hoc analysis, that systolic blood pressure, diastolic blood pressure, and mean arterial blood pressure were significantly lower in volunteers who had taken CBD, especially immediately after the stress tests.
It also lauds itself for being the only traceable study of its kind that conclusively shows that "acute administration of CBD reduces resting blood pressure, with a lower stroke volume and a higher heart rate."
According to the authors, other studies in humans have not shown that CBD significantly affects baseline cardiovascular parameters. Yet, they point out that this may be due to study design and the fact that the other subjects were not "cannabis naive." Since tolerance can be developed to the hemodynamic response to cannabinoids in humans, this may explain the differences between studies, according to the authors.
They also conceded that their conclusions "...may reflect the anxiolytic and analgesic effects of CBD, as well as any potential direct cardiovascular effects," so suffice it to say that more clinical studies are needed before it can be said with certainty that acute dosing with CBD lowers blood pressure.
Cannabidiol is well known for its positive effect on anxiety, as many can attest. They are supported by science in this.
A New York-based review of the literature, published in 2015, concluded that current evidence indicates CBD has considerable potential as a treatment for multiple anxiety disorders. The reviewers also point out the great need for further study of CBD's chronic and therapeutic effects in relevant, clinical populations.
They furthermore say that preclinical evidence strongly supports CBD as a treatment for:
While anxiety doesn't cause hypertension or high blood pressure, it has been shown that episodes of anxiety can cause dramatic, temporary spikes in your blood pressure. This, in turn, can cause blood vessel and organ damage.
Writing for Mayo Clinic, Dr. S.G. Sheps also points out that when you experience anxiety, you're more likely to resort to other unhealthy habits that can increase your blood pressure, such as smoking, drinking too much alcohol, and overeating. 
So, while we cannot conclusively answer in the affirmative the question "Does CBD oil lower blood pressure?" we can speculate with some impunity that CBD protects your cardiovascular, neurologic, and organ health. As said, however, never attempt to replace any pharmaceutical drug with CBD without your doctor's prior consent.