Cannabis Side Effects: Common Reactions and Risks

Cannabis side effects depend on the dose, the product, and the person using it. The most common short-term effects are dry mouth, red eyes, drowsiness, slower reaction time, and trouble with short-term memory. Higher doses of THC are more likely to bring anxiety, paranoia, a racing heart, or nausea, and edibles can cause these effects hours after you eat them.

short term effects of cannabis on the body

Common short-term cannabis side effects

Most unpleasant reactions fade within a few hours, though edible effects can last longer. Typical effects include:

short term effects of cannabis on the body

• Dry mouth and dry eyes
• Drowsiness or feeling sluggish
• Slower reaction time and reduced coordination
• Short-term memory lapses and trouble concentrating
• Increased heart rate, sometimes with palpitations
• Anxiety, racing thoughts, or paranoia
• Nausea, dizziness, or headache

These effects are usually stronger in people who are new to cannabis, who use high-THC products, or who take a large dose by accident.

long term health risks of smoking weed

How THC and CBD differ

THC is the compound responsible for the psychoactive high and for most side effects people notice. CBD does not produce a high, but it is not side-effect free. Some users report drowsiness, dry mouth, stomach upset, or loose stools. CBD can also change how the body breaks down certain prescription drugs, which can raise the level of those drugs in your bloodstream.

cannabis withdrawal symptoms and side effects

Side effects by consumption method

The method you choose changes how fast effects arrive and how long they last.

• Inhalation (flower, vape, concentrate): Effects start within minutes and fade in one to three hours. Smoke and vapor can irritate the throat and lungs and cause coughing.
• Edibles and drinks: Effects can take 30 minutes to two hours to appear and may last six hours or more. Because the delay is long, it is easy to take more before the first dose hits.
• Tinctures and oils: Placed under the tongue, these often work faster than edibles but slower than inhalation.
• Topicals: Creams and balms are not absorbed into the bloodstream in meaningful amounts, so they rarely cause psychoactive effects. Skin irritation is the main concern.

Side effects that need medical attention

Most cannabis side effects are uncomfortable rather than dangerous, but some signs call for help right away.

• Chest pain, fainting, or a heart rate that will not settle
• Severe confusion, hallucinations, or thoughts of self-harm
• Repeated vomiting, especially with stomach pain or dehydration
• Panic that does not ease after a few hours

In the United States, Poison Control can be reached at 1-800-222-1222 for guidance on a possible overdose. Call 911 for chest pain, loss of consciousness, or any life-threatening symptom.

Who should avoid cannabis

Some groups face a higher risk of serious reactions and are advised to skip cannabis entirely:

• Anyone under 21, since cannabis can affect the developing brain
• People who are pregnant or breastfeeding
• People with a personal or family history of psychosis or schizophrenia
• People with certain heart conditions or uncontrolled blood pressure
• Anyone taking medications that interact with cannabis, including blood thinners, sedatives, and some antidepressants

How to lower your risk of side effects

1. Start with a low dose, especially with edibles, and wait at least two hours before taking more.
2. Check the THC content on the label. A product with 25 mg of THC per serving hits very differently than one with 5 mg.
3. Choose a balanced product with some CBD if anxiety is a concern for you.
4. Avoid mixing cannabis with alcohol or other sedatives.
5. Drink water and eat something if you feel lightheaded.
6. Keep notes on what you used, how much, and how you felt so you can repeat what works.

How long do cannabis side effects last?

Inhaled effects usually fade within one to three hours. Edible effects can last six hours or longer, and lingering grogginess may carry into the next day after a large dose.

Can you overdose on cannabis?

A cannabis overdose is rarely fatal, but it can cause intense anxiety, vomiting, and confusion. Severe cases may need emergency care, so treat any frightening reaction seriously.

Does cannabis interact with medications?

Yes. Cannabis can change how the liver processes some drugs, which may strengthen or weaken their effects. Talk with a pharmacist or doctor before combining cannabis with prescription medication.