Heroin is made from morphine, a substance that comes from the opium poppy. The drug produces a pleasurable and relaxed sensation. But it also causes many negative mental and physical side effects. An overdose can be fatal.

Heroin is a highly addictive drug and the withdrawal symptoms can be painful. Learn about heroin and how it affects the brain and body.

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About heroin

Heroin (also known as dope, dust, junk, smack and horse) is a depressant. It slows down the activity of the nervous system.

Pure heroin is a fine, white, bitter-tasting powder. However, it is frequently mixed with other things that look similar to it. These include sugars, starch or quinine (a drug made from cinchona bark).

When sold on the street, heroin may vary in colour, consistency and purity, depending on how it is made. It may look like white powder, a brown grainy substance or a dark sticky gum.

Heroin is consumed in several ways. The powder may be:

  • sniffed up the nose
  • smoked (known as chasing the dragon)
  • dissolved in water
    • injected into a vein (known as mainlining)
    • injected into a muscle or under the skin (known as skin-popping)

How quickly heroin affects a person depends on how it is taken. When heroin is injected, it quickly enters the brain and produces a pleasurable feeling. This occurs within seconds and lasts anywhere from 45 seconds to a few minutes. When smoked or snorted, the effects are less intense.

A period of tranquillity or sedation that may last up to about an hour follows. When heroin is injected in a muscle or under the skin, the effects occur more slowly, usually within 10 minutes.

The effects of heroin usually last for about 3 to 5 hours. To avoid symptoms of withdrawal, individuals who use heroin may feel the need to use every 6 to 12 hours.

While heroin use produces pleasant feelings, it also has less desirable effects.

Short-term effects of heroin

Heroin use can lead to short-term mental and physical effects.

Mental effects

Short-term effects include:

  • dizziness
  • confusion

Physical effects

Short-term effects include:

  • drowsiness
  • nausea and vomiting
  • constricted pupils
  • itching or burning sensation of the skin
  • headaches
  • slowed breathing


The risk of a heroin overdose is high. Individuals rarely know the actual strength of the drug they take. The drug takes effect very quickly, especially when injected. A person who takes too much may lose consciousness almost immediately.

Symptoms of an overdose include:

  • clammy or bluish skin
  • slowed breathing
  • loss of consciousness
  • vomiting

In large enough quantities, heroin can suppress breathing, which can be fatal.

An overdose is more likely if heroin is taken along with other depressant drugs. Combining drugs can increase each drug's effects and puts a person at increased risk of overdosing. These include:

In cases of an overdose, a drug called naloxone can block the depressant effects of heroin. Learn more about opioid overdoses.

Remember that if you or someone else is in need of medical help, you do not need to be afraid of police involvement. Saving a life is the number one priority for emergency responders. Canada’s Good Samaritan Drug Overdose Act protects individuals who seek help for an overdose from charges and conditions related to the possession of drugs.

Long-term effects of heroin

With long-term use, heroin has many harmful effects on a person's body and mind. The more a person uses heroin, the more their health is affected.

Mental effects

Long-term heroin use can cause:

  • learning and memory problems
  • difficulty controlling impulsive behaviour
  • lack of emotion (apathy)
  • unstable moods
  • depression

Physical effects

Many long-term physical effects of heroin use are due to using unclean needles and syringes. Sharing drug equipment can lead to:

  • infectious diseases, such as:
  • blood poisoning
  • skin sores
  • infection of the lining of the heart

Other effects include:

  • insomnia
  • constipation
  • sexual problems in men
  • irregular menstrual cycles in women
  • collapsed veins
  • liver and kidney disease
  • substance use disorder

Heroin use during pregnancy can be harmful to an unborn child. It is associated with:

  • premature delivery
  • low birth weight
  • high infant mortality

Substance use disorders and withdrawal

Physical dependence and substance use disorder can develop quickly – within weeks of regular use. The need to get heroin can take over a person’s life.

The severity of withdrawal symptoms from heroin depends on the:

  • amount and frequency of use
  • length of time a person has used the drug
  • person's health
  • conditions under which withdrawal happens

Symptoms of withdrawal from heroin can begin 8 to 12 hours after the last dose. Symptoms may reach their peak between 24 and 48 hours. They subside substantially after about 5 days to a week. Individuals will often inject heroin to avoid withdrawal symptoms.

In addition to intense cravings for the drug, during the withdrawal period, a person may experience:

  • abdominal cramping
  • nausea, vomiting and diarrhea
  • insomnia
  • a racing heartbeat
  • involuntary muscle spasms
  • anxiety, restlessness and depression
  • sweating or cold flashes with goose bumps (also known as "cold turkey")

Heroin withdrawal is rarely fatal for adults.

A substance use disorder to heroin can be treated with medications such as buprenorphine and methadone. Opioid substitution treatments work by binding to the same receptors as heroin. Treatment can prevent heroin withdrawal and reduce or eliminate the cravings.

A child may be born with withdrawal symptoms. A baby going through heroin withdrawal may be:

  • irritable
  • cry excessively
  • be sweaty
  • exhibit shaky or jerky movements

The baby may have trouble feeding or have diarrhea and a need to vomit. A baby with severe heroin withdrawal can develop seizures and die. Babies undergoing withdrawal need to be treated in a hospital.

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