What THC does to the body

THC binds to CB1 receptors in the brain and CB2 receptors in the immune system. CB1 receptors sit in the heart, blood vessels, gut, and salivary glands. Physical effects start within minutes when smoked or vaped. They start in 30 to 60 minutes when eaten.

physical side effects of thc

Heart and circulation

Heart rate

THC raises resting heart rate by 20 to 50 beats per minute. The peak comes 10 to 30 minutes after smoking. Heart rate stays elevated for up to 3 hours. A 2021 study in the Journal of the American Heart Association found cannabis use linked to a higher risk of heart attack in the hour after use.

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Blood pressure

Blood pressure can drop, causing dizziness and fainting. It can also rise in some people. Standing up after using THC can cause a sudden drop.

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Eyes, mouth, and skin

Red eyes come from dilated blood vessels in the conjunctiva. Dry mouth comes from reduced saliva flow. These effects last 1 to 4 hours. Sweating and flushing can occur.

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Stomach and gut

THC can reduce nausea at low doses. At high doses, it can cause vomiting. Cannabinoid hyperemesis syndrome (CHS) causes repeated vomiting, abdominal pain, and a strong urge to take hot showers. CHS occurs in chronic daily users. Emergency room visits for CHS rose in states with legal cannabis.

Coordination and muscles

THC impairs balance, reaction time, and hand-eye coordination. Muscles may feel relaxed or heavy. Driving within 3 hours of use raises crash risk.

Lungs

Smoking THC exposes the lungs to tar and irritants. Symptoms include cough, wheezing, and phlegm. Vaping THC with vitamin E acetate caused EVALI. CDC counted 2,807 hospitalizations and 68 deaths in 2019 and 2020.

How long effects last

Inhaled THC: 1 to 3 hours for most physical effects. Edibles: 4 to 6 hours, with peak at 2 to 3 hours. High doses last longer.

When to get help

Seek medical care for chest pain, severe vomiting, fainting, or trouble breathing.