Getting high from cannabis typically raises your blood pressure in the short term, not lowers it. This surprises many people, but research consistently shows that THC increases both systolic and diastolic blood pressure within minutes of inhaling. The full picture is more complicated, though, because cannabis triggers a sequence of cardiovascular changes that can include a blood pressure drop later, especially when you stand up.
What Actually Happens to Blood Pressure Right After Use
Within minutes of smoking or vaping THC-dominant cannabis, your blood pressure rises modestly. A study published in Circulation measured an average increase from 109/64 to 113/69 mmHg, with mean arterial pressure climbing about 5 points. That bump is relatively small for most healthy people, but it happens reliably regardless of whether you smoke or vape.
At the same time, your heart rate jumps significantly. Cannabis can increase heart rate by 20% to 100%, and that elevated rate can persist for two to three hours. This spike happens because THC causes blood vessels to widen (reducing resistance), and your heart compensates by beating faster to maintain blood flow. That reflex is the reason many people feel their heart pounding after using cannabis.
Animal research has mapped out a three-phase blood pressure response to THC: an immediate brief drop, followed within about 30 seconds by a rise in blood pressure from vessel constriction, and then a longer-lasting drop driven by reduced activity in the nervous system pathways that keep blood pressure elevated. In practice, what most people experience is the middle phase (the rise) and sometimes the later drop, particularly if they stand up quickly.
Why Some People Feel Dizzy or Faint
Even though cannabis raises blood pressure overall while you’re sitting or lying down, it can cause a noticeable drop when you stand. This is called orthostatic hypotension, and it’s one of the most recognized side effects. THC relaxes blood vessel walls by triggering the release of nitric oxide, a molecule that signals vessels to dilate. When you’re horizontal, this widening doesn’t cause problems. But when you stand, gravity pulls blood toward your legs, and your relaxed blood vessels can’t constrict fast enough to push it back up to your brain.
The result is dizziness, lightheadedness, or even fainting. Higher doses make this more likely. If you’ve ever stood up too fast after getting high and felt the room tilt, this is the mechanism behind it. It’s not that cannabis lowered your overall blood pressure in a sustained, therapeutic way. It’s that the normal reflex your body uses to adjust blood pressure to position changes gets temporarily blunted.
THC vs. CBD: Different Effects on the Heart
THC and CBD affect blood pressure differently. Research published in the Journal of the American Heart Association directly compared the two and found that THC-dominant cannabis raised heart rate by about 16 to 17 beats per minute and mean arterial pressure by 5 to 7 mmHg. CBD-dominant cannabis, by contrast, produced no meaningful change in either heart rate or blood pressure.
The same study found that THC impaired markers of how well the heart relaxes between beats (diastolic function), while CBD did not. The researchers concluded that THC appears to be the primary driver of the cardiovascular effects people experience from cannabis. If you’re using a CBD-only product, you’re unlikely to notice any blood pressure changes at all.
Does Long-Term Use Change Baseline Blood Pressure?
People who use cannabis regularly over months or years sometimes wonder whether it’s slowly raising or lowering their resting blood pressure. The available longitudinal research suggests it does neither. Studies tracking cannabis users over time, including findings from the Multi-Ethnic Study of Atherosclerosis, have found no association between regular use and elevated systolic or diastolic blood pressure, and no increased incidence of hypertension.
Interestingly, chronic use does seem to change how the body responds to cannabis itself. Regular users develop tolerance to the heart rate spike and the orthostatic hypotension. Their blood volume increases slightly, and their cardiovascular system shifts toward a calmer baseline state with lower sympathetic nervous system activity. In other words, the acute effects that new or occasional users feel strongly tend to fade with repeated use.
Cardiovascular Risks Beyond Blood Pressure
Even though cannabis doesn’t appear to cause lasting changes in blood pressure, it’s not cardiovascularly harmless. Daily cannabis use has been associated with higher rates of heart attack and stroke in large population studies. The American Heart Association has flagged this connection, noting that the data is consistent across multiple studies. The exact mechanism isn’t fully understood, but the repeated stress of heart rate spikes, temporary blood pressure swings, and reduced diastolic function likely plays a role over time.
These risks are most relevant for people who already have heart disease, high blood pressure, or other cardiovascular risk factors. For a young, healthy person using cannabis occasionally, the acute blood pressure and heart rate changes are temporary and generally well-tolerated. But for someone with an underlying heart condition, the combination of a 20% to 100% heart rate increase and fluctuating blood pressure creates a window of vulnerability each time they use.
The Bottom Line on Cannabis and Blood Pressure
Cannabis does not lower blood pressure in the way some people hope. THC raises blood pressure and heart rate acutely, and while it can cause position-related drops that feel like low blood pressure, that effect is a temporary disruption of normal cardiovascular reflexes rather than a beneficial reduction. Long-term use doesn’t appear to shift baseline blood pressure in either direction, but it does carry cardiovascular risks that go beyond blood pressure numbers alone. If you’re taking blood pressure medication or managing a heart condition, the unpredictable swings cannabis causes are worth taking seriously.