Substance use

Substance use is a broad term for using alcohol, nicotine, medicines, or other drugs. It describes an activity, not a disease or diagnosis.

Substances may be legal, prescribed, sold without a prescription, or illegal. Examples include alcohol, tobacco and nicotine products, cannabis, opioid pain medicines, sleeping pills, stimulants like methylphenidate or lisdexamfetamine, inhalants, and drugs such as heroin or cocaine.

Use can range from occasional exposure to regular or compulsive use. Taking a prescribed medicine exactly as directed is also substance use, although it is different from taking that medicine in an unsafe or unintended way.

Clinicians may use the term substance use disorder when a pattern of use causes significant problems or loss of control. This is a medical diagnosis based on a careful assessment. A person does not have a substance use disorder simply because they use a substance or have a positive drug test.

Words such as “abuse” can carry judgment. Clearer terms include substance use, risky use, non-medical use, and substance use disorder.

Substances enter the body by being swallowed, inhaled, smoked, injected, or absorbed through the skin or lining of the mouth. The route affects how quickly the substance reaches the bloodstream and brain.

Different substances act in different ways. Some slow brain activity, some increase alertness, and some change perception, mood, pain, or coordination. Effects also depend on the amount used, product strength, other substances taken, health conditions, age, and previous exposure.

Several related terms have distinct meanings:

• Intoxication means temporary changes in thinking, behaviour, coordination, or body function after recent use
• Tolerance means the same amount has less effect over time
• Physical dependence means the body has adapted to regular exposure
• Withdrawal means physical or emotional changes after reducing or stopping a substance
• Substance use disorder means an ongoing pattern involving impaired control, health risks, or major problems in daily life

Tolerance and physical dependence can develop while someone takes a medicine as prescribed. They do not, by themselves, mean that the person has an addiction.

Combining substances can change their effects. Alcohol, opioids like oxycodone or morphine, and sedating medicines can all slow breathing and alertness. Using them together can be much more dangerous than using one alone.

Substance use can affect judgment, reaction time, sleep, mood, memory, blood pressure, breathing, and coordination. The effects may matter when driving, swimming, working with machinery, caring for someone, or making important decisions.

Regular use may also interact with health conditions or treatments. For example, a substance may make a medicine less effective, increase side effects, or hide signs that a condition is getting worse. A pharmacist can check for known interactions involving prescription medicines, non-prescription products, supplements, alcohol, or other drugs.

Pregnancy and breastfeeding can change the health considerations. Some substances can reach the fetus or pass into breast milk. If you are pregnant, breastfeeding, or planning pregnancy, discuss your use and medicines with a prenatal clinician. Do not stop a prescribed medicine suddenly unless you have been told how to do so safely.

The source of a product also matters. Counterfeit pills and unregulated drugs may contain unexpected ingredients or strengths. Appearance alone cannot confirm what they contain.

Problems linked with substance use include accidental injury, poisoning, overdose, harmful interactions, withdrawal, and substance use disorders. Use can also contribute to relationship, work, school, financial, or legal difficulties.

An overdose happens when a substance causes toxic effects that the body cannot safely manage. It may be accidental. Risk can rise when substances are combined, after a period of not using, or when product strength is unknown.

Alcohol and sedative medicines such as benzodiazepines like diazepam or lorazepam can cause dangerous withdrawal in someone whose body has become dependent. Severe withdrawal may involve seizures, hallucinations, or profound confusion. Stopping regular heavy use suddenly without medical support may not be safe.

Injection can lead to skin infections and infections passed through blood, including hepatitis B, hepatitis C, and HIV. Smoking or inhaling substances can injure the lungs. Impaired judgment can also increase the chance of falls, crashes, violence, or sex without intended protection.

Call emergency services now if someone:

• Cannot be woken or has collapsed
• Is breathing very slowly, irregularly, or not at all
• Has blue, grey, or unusually pale lips or skin
• Has a seizure, severe breathing trouble, or new chest pain
• Has severe confusion, hallucinations, or extreme agitation
• May have overdosed or taken an unknown substance
• Is at immediate risk of harming themselves or someone else

If an opioid overdose may be involved, give naloxone if it is available and you know how to use it. Call emergency services even if the person wakes up. Stay with them, place them on their side if they are breathing, and follow the emergency operator’s instructions. Do not make them vomit.

Seek prompt medical advice for possible withdrawal, increasing loss of control, repeated blackouts, an infected injection site, use during pregnancy, or substance use that is interfering with health or daily life. These concerns need timely assessment but are not always emergencies.

You can give a clinician or pharmacist an accurate list of what you use. Include alcohol, nicotine, cannabis, prescription medicines, non-prescription products, supplements, and other drugs. Note how often you use them and whether you combine them.

Useful actions include:

• Ask whether a substance could interact with your medicines or conditions
• Keep prescription medicines in their original containers
• Do not share medicines or take pills prescribed for someone else
• Avoid driving or hazardous tasks when your judgment may be affected
• Record changes in amount, frequency, cravings, blackouts, or withdrawal
• Ask about confidential screening and treatment options if you are concerned
• Ask a pharmacist or community service about naloxone if opioid exposure is possible

Screening questionnaires can identify patterns that may need a closer look. Examples ask about frequency, loss of control, consequences, and attempts to cut down. Screening is not the same as diagnosis.

Blood, urine, saliva, or hair tests can sometimes show exposure to particular substances. Their detection windows differ. A positive result usually cannot show the exact amount taken, prove current impairment, or diagnose a substance use disorder by itself.

If you regularly use alcohol, benzodiazepines, or another sedating medicine, ask how to reduce safely before stopping. Medical support may include monitoring, counselling, medicines, or a structured withdrawal plan.

Does any substance use mean addiction?

No. Substance use covers many situations, including prescribed treatment and occasional use. Addiction generally involves impaired control and continued use despite harm. A clinical assessment is needed to diagnose a substance use disorder.

Can prescribed medicines cause dependence?

Yes. Some medicines can lead to physical dependence even when taken correctly. This means stopping suddenly may cause withdrawal. It does not necessarily mean you have lost control over use.

Does a positive drug test show impairment?

Usually not. It may show that a substance or its breakdown products were present during a certain period. It often cannot establish when the substance was taken or whether it was affecting you at the time of testing.

Is there one safe amount for every substance?

No. Risk depends on the substance, strength, route, pattern of use, other substances, and your health. Unregulated products may not contain what their label or appearance suggests.

Can treatment help if use feels difficult to control?

Yes. Treatment can include counselling, peer support, medicines for certain substance use disorders, and care for related physical or mental health needs. An assessment can help identify which options fit your goals.