Cannabis and your heart: what to know
Cannabis briefly speeds up your heart and shifts your blood pressure. Harmless for most, but worth understanding, especially with a heart condition.
Most people notice it eventually: a faster heartbeat soon after using cannabis. It’s one of THC’s most reliable physical effects, and for the most part it’s harmless. But it’s worth understanding what’s happening, and when to pay attention.
What cannabis does to your heart
Shortly after you use cannabis, THC tends to:
- Speed up your heart rate, sometimes by 20 to 50 beats per minute, usually for a few minutes up to a couple of hours.
- Shift your blood pressure, often a brief rise, then a drop, which is part of why you can feel lightheaded or get red eyes.
For a healthy heart, this is generally well tolerated and temporary. Your body handles the brief bump and returns to normal as the THC clears.
When it matters more
The extra demand on your heart is a bigger deal if your heart is already under strain. Be cautious, and talk to a doctor first, if you have:
- Heart disease or a previous heart attack
- An irregular heartbeat (arrhythmia)
- High blood pressure
- A history of stroke
There’s some evidence the strain is highest in the first hour after use, which is worth keeping in mind if you have risk factors.
High doses and the racing-heart feeling
A big dose of THC, especially from an edible, can bring on a pounding or racing heart, usually together with anxiety. It feels alarming but is the same passing reaction as greening out: find a calm spot, slow your breathing, and wait. But chest pain, fainting, or severe symptoms are reasons to seek medical care, not tough it out.
Lowering the risk
- Start low, especially with edibles, to avoid the big dose that triggers a racing heart.
- Favour lower-THC or balanced products if you’re prone to palpitations or anxiety. CBD doesn’t cause the same spike.
- Don’t stack stimulants. Pairing cannabis with lots of caffeine or other stimulants adds to the heart-rate effect.
- Know your history. If you have any heart condition, treat cannabis as something to clear with your doctor.
This isn’t a reason to be afraid of cannabis, but your heart is one part of your body where “start low and go slow” really earns its keep. See cannabis and your health for the bigger picture.
Sources
- Health Canada, Cannabis health effects
- Heart and Stroke Foundation of Canada, cannabis and heart health
Frequently asked questions
Does cannabis raise your heart rate?
Yes. THC typically speeds your heart up soon after use, sometimes by 20 to 50 beats per minute, for anywhere from a few minutes to a couple of hours. For most healthy people it's harmless and passes.
Is cannabis bad for your heart?
For most healthy adults, occasional use is low-risk. But the heart-rate spike and blood-pressure changes can add strain, which matters more if you have a heart condition or risk factors.
Who should be careful with cannabis and their heart?
Anyone with heart disease, a heart-rhythm problem, high blood pressure, or a history of heart attack or stroke should be cautious and talk to a doctor before using cannabis.
Why is my heart racing after an edible?
A high dose of THC can cause a pounding or racing heart, often alongside anxiety. It's the same effect as a 'greening out' episode. Sit calmly, breathe, and it passes, but seek care for chest pain or severe symptoms.
Know your local rules
Legal age, where to buy, and where you can use it all change by province.
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