Immediate health effects

The effects of marijuana use can be different for everyone. Common effects may include:
  • A happy, relaxed or “high” feeling.
  • Slower reactions and hand/eye coordination.
  • Distorted perceptions of time and distance.
  • Trouble thinking, learning and remembering.
  • Anxiety, panic or paranoia.
  • Faster heart rate.
  • Increased blood pressure.
  • Less interest in normal activities.
  • Increased appetite.
  • Dry mouth.
  • Red eyes.
  • Psychosis — seeing or hearing things that aren't real (more common with higher doses of THC).
These effects typically last two to four hours after marijuana is smoked or inhaled. When marijuana is eaten, the effects take longer to start and may last four to 10 hours. Marijuana can vary in its potency, or strength, depending on the plant and extraction process.

For occasional users, using 10 mg or more of THC is likely to cause impairment. This impacts your ability to drive, bike or perform other safety-sensitive activities.
People may think that they’re “safer” drivers while stoned since they drive more slowly. However, research shows that driving while high may increase your risk of a crash. If you’re high, you shouldn’t drive, bike or operate machinery. 
  • Smoking:
    • Wait at least six hours after smoking up to 35 mg of THC before driving or biking. If you’ve smoked more than 35 mg, wait longer.
  • Eating or drinking:
    • Wait at least eight hours after eating or drinking up to 18 mg of THC before driving or biking. If you’ve consumed more than 18 mg, wait longer.
  • Marijuana affects individuals differently.  
  • Multiple substances:
    • Using alcohol and marijuana at the same time is likely to result in greater impairment than either one alone.
Vape products can contain nicotine, marijuana (THC or CBD), or other substances like flavoring agents or additional chemicals. While vaping products have grown in popularity, we have seen outbreaks of lung illnesses linked to vaping. The long-term health effects of vaping are unknown, and as information on the illness emerges, our best advice is to not vape at all. See here for Colorado-specific updates on the outbreak.
Used too much?
The symptoms of using too much marijuana are similar to the typical effects of using marijuana, but more severe. These symptoms may include:
  • Extreme confusion, anxiety, panic or paranoia.
  • Fast heart rate.
  • Hallucinations or delusions.
  • Increased blood pressure.
  • Severe nausea and vomiting.
Increasing numbers of people are going to the emergency room after using marijuana, possibly because they used too much. This may happen because they:
  • Thought a marijuana product was regular food.
  • Used a product with more THC than they thought, either because they’re using marijuana for the first time or trying a high-THC product.
  • Consumed homemade edibles without a clear understanding of the THC content.
  • Consumed more marijuana edibles than they needed since they didn’t feel the effects right away. The effects of marijuana edibles may take up to four hours to peak after ingesting.
If you or someone you know has any of the symptoms above, call the poison control hotline at 1-800-222-1222 for free, fast, expert help anytime. If the symptoms are severe, call 911 or go to an emergency room.
All information on the health effects of marijuana is taken from the Retail Marijuana Public Health Advisory Committee’s systematic review of available, high-quality research. For more information about its findings, review Monitoring Health Concerns Related to Marijuana in Colorado: 2016.