What are the effects of taking drugs?

Drugs have different effects depending on the drug itself, the person taking it and their surroundings. Learn how your body processes drugs and about the short-term and long-term effects. Taking drugs can affect not just your physical and mental health, but your whole life. Just one pill can kill.

Drugs affect your whole life

Drugs don’t just affect your physical body and health, they can affect your mental health, your finances, your relationships, your social life and your criminal record.

Physical effects can vary

The way a drug affects you depends on:

  • the drug itself
    • what type of drug it is
    • how you took it
    • how much you took
    • how strong or pure it is
    • how often you take it
  • your own body
    • your gender
    • physical size
    • mood
    • personality
    • expectations
    • how recently you ate
    • your general health
    • have you become tolerant?
    • what other drugs you took with it – for example, alcohol.

Each drug causes different physical reactions, depending on the type of drug. Some will make you feel more awake, alert and energetic. Others will give you a calm, relaxed feeling. Some alter your perceptions and can cause hallucinations. Others may make you feel numb.

Long-term use and larger doses have negative effects that can seriously harm your health, even cause death, including disease risks from sharing needles, and permanent damage to the brain and other organs.

Visit the Alcohol and Drug Foundation website to learn about individual drugs and their effects.

Other effects

Mental health

Studies show that drug use increases your risk of mental health issues such as anxiety, depression and psychosis. People with mental health issues also have a higher rate of drug use problems.

Financial issues

Some drugs can be very expensive – the street price of illicit drugs depends on availability and demand. If you have become dependent on a drug, you could end up in financial trouble.

Illicit drug use causes a significant burden to the Australian economy. For example, the estimated total social costs for methamphetamine alone are around $5 billion annually – through crime, loss of productivity and increased health care costs.


Because drugs can change your behaviour, they can affect your relationships with family and friends. There is an increased risk of injury and/or assault to both yourself and other people.

Legal issues

Many drugs are illegal and you can be fined, or sent to prison, for having them. If convicted of a drug offence, you could end up with a criminal record – this can make it harder to get a job, apply for a loan, or travel overseas.

Learn more about Australia’s drug laws.

Drugs in sport

Sports people and professional athletes who use illegal substances risk damaging not only their physical health, but also their reputation and the integrity of their sport.

The Australian Sports Anti-Doping Authority (ASADA) protects the health of athletes and implements anti-doping programs, including drug testing.

Drugs and driving

Alcohol and other drugs can seriously affect your driving skills. You are more likely to have an accident, injuring yourself and/or others. The crash could be fatal.

The different types of drugs affect your driving ability in the following ways:

  • stimulants – driving too fast or erratically, being aggressive behind the wheel, reduced vision, you can feel overconfident
  • depressants – driving too slowly, falling asleep at the wheel, veering out of your lane, your reactions are slower
  • hallucinogens – distorted vision, hard to correctly judge distances, seeing things that aren’t there.

Mixing drugs, including alcohol, only increases your risk of having a crash.

It's illegal to have any trace of illicit drugs in your system when driving.

Learn more about the consequences of driving under the influence of alcohol and other drugs on the Alcohol and Drug Foundation website.

How your body processes drugs

Your body processes drugs in 4 stages:

  1. Absorption

    When you use a drug it is absorbed into your bloodstream. How quickly this happens depends on how you took the drug.
  2. Distribution

    Once a drug is in your bloodstream it circulates through your body, being distributed to different organs and the brain. The drug affects chemicals and receptors within the brain, causing different effects depending on the type of drug.
  3. Metabolism

    Your body then metabolises the drug or breaks it down into simpler molecules (known as metabolites) which can be more easily eliminated. Sometimes these metabolites can also affect your body.
  4. Excretion

    Metabolised drugs go through your digestive system and exit your body, usually in urine or faeces.

How long your body takes to eliminate a drug varies. It depends on many factors, including the drug itself (how much you took, how strong, etc) and you as an individual (your metabolism, age, health, environment, etc).

Read more about how drugs are detected.

Come down

As drugs are processed and eliminated from your body, the effects wear off – you experience a ‘come down’. The after-effects vary depending on what drugs were taken and can be mental and/or physical. They commonly include:

  • depression
  • insomnia or sleepiness
  • extreme tiredness.

You may also experience:

  • headaches
  • nausea
  • loss of appetite.

Read more about managing the effects of a come down on the ReachOut website.

Drug tests

Testing to see if there are drugs in your body may be done:

  • to detect illegal drug use
  • when you’re driving
  • in some workplaces
  • in sports.

There are different types of drug tests – they look for traces of drugs in your:

  • saliva
  • blood
  • urine
  • breath
  • sweat
  • hair.

A negative test result only happens if:

  • you have not taken any drugs
  • your body has broken down the drug and eliminated it from your body.

Drugs stay in your system for varying lengths of time. Visit the Drug Aware website for more information on how long drugs can be detected.

What is a bad reaction or ‘trip’?

A person using drugs can sometimes have a bad reaction – also called a ‘bad trip’. This is often linked to hallucinogenic drugs.

The intensity of the high experienced during a bad trip can be overwhelming and frightening and the user can become unstable, even violent. They risk harming themselves and/or others around them.

Contact the National Alcohol and Other Drug Hotline if you need help or advice. Of course, if it’s an emergency, phone 000 and ask for an ambulance.

Drug overdose

Taking too much of a drug, including prescription drugs, can result in an overdose. Each person will react differently, but death can occur in some cases. Even if the person recovers there can be permanent damage to their body.

If you or someone you know is at risk of overdosing, this is a medical emergency. Phone 000 immediately and ask for an ambulance.

Polydrug use

Mixing drugs or taking multiple drugs together is known as polydrug use. Examples of polydrug use include:

  • smoking cannabis after drinking alcohol
  • mixing alcohol with energy drinks containing caffeine
  • combining alcohol with prescription drugs.

This can be extremely dangerous as the effects can be unpredictable — they will depend on which drugs have been taken together. For example, combining drugs with similar effects (stimulants, depressants or hallucinogens) increases the impact on your body.

Read more about mixing drugs on the Drug Aware website.

Drug addiction and dependence

Anyone can become addicted to alcohol or drugs.

Not everyone who tries drugs will become regular users, and not all regular users become dependent. There are many factors involved and it varies between people and drugs.

Using a drug regularly can lead to tolerance – your body becomes used to the drug and needs increasingly larger doses to achieve the same effect.

Regular use can also lead to dependence – where you need the drug to feel good and function normally. Dependence can be physical, psychological or both.

Being addicted means continuing to use a drug even though you’re aware of the harmful consequences. Addiction can be:

  • physical – your body craves the drugs, for example, alcohol, nicotine
  • mental – your mind needs the drug in order to forget your problems or relax
  • social – you feel you need the drug in order to fit in or enjoy social events.

If you stop taking a drug or try to reduce the amount you’re taking you may experience withdrawal symptoms. These can be physically and mentally unpleasant and may include:

  • tiredness
  • hunger
  • depression
  • being irritable
  • aggression
  • anxiety
  • paranoia
  • cravings for the drug.

Learn more about withdrawal on the Alcohol and Drug Foundation website.

Find out how you can reduce or quit drugs.

Date last updated:

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