Unconsciousness is a medical emergency that can occur suddenly and without warning. While some episodes, such as simple fainting. It can be brief and harmless or a sign of a serious medical emergency.
In Australian first aid education, the acronym FISHSHAPED is a helpful memory tool for the common causes of unconsciousness:
Below is a detailed overview of each cause, based on guidance from trusted Australian health authorities including healthdirect Australia, Heart Foundation, Stroke Foundation, Diabetes Australia, and Better Health Channel.
Fainting (Syncope): The Most Common Cause of Temporary Unconsciousness
Fainting — also known as syncope — is a brief loss of consciousness caused by a temporary drop in blood flow to the brain.
According to healthdirect Australia, common triggers include:
- Dehydration
- Standing up too quickly
- Prolonged standing
- Emotional stress or pain
- Heat exposure
Before fainting, a person may feel dizzy, lightheaded, nauseous, sweaty, or have blurred vision.
Most fainting episodes are short and recovery is quick once the person lies flat. However, recurrent fainting, fainting during exercise, or fainting with chest pain should be medically assessed, as it may signal heart rhythm problems.
Imbalance of Temperature: Heatstroke and Hypothermia Risks in Australia
Australia’s climate makes temperature-related illness particularly relevant.
Heatstroke
Heatstroke occurs when the body temperature rises above 40°C and the body cannot cool itself effectively. The Better Health Channel warns that symptoms may include:
- Confusion
- Collapse
- Seizures
- Loss of consciousness
Heatstroke is a medical emergency and requires immediate cooling and urgent medical assistance.
Hypothermia
Hypothermia occurs when body temperature drops below 35°C. While less common in many parts of Australia, it can occur in alpine regions or after prolonged exposure to cold water.
Severe hypothermia can cause slowed breathing, confusion, and unconsciousness.
Shock: A Life-Threatening Circulatory Failure
Shock happens when the body’s tissues do not receive enough oxygenated blood. Causes include:
- Severe bleeding
- Major burns
- Serious infection (septic shock)
- Allergic reaction (anaphylactic shock)
The Better Health Channel explains that signs of shock include:
- Pale, cold, clammy skin
- Rapid pulse
- Shallow breathing
- Confusion or agitation
- Collapse
Without urgent treatment, shock can rapidly lead to unconsciousness and organ failure.
Head Injury: Traumatic Brain Injury (TBI)
A significant blow to the head can disrupt normal brain function and cause temporary or prolonged unconsciousness.
According to Healthdirect Australia, warning signs after a head injury include:
- Loss of consciousness (even briefly)
- Persistent headache
- Vomiting
- Confusion or drowsiness
- Seizures
Any loss of consciousness following a head injury requires urgent medical assessment, as bleeding inside the skull can worsen over time.
Stroke: When Blood Flow to the Brain Stops
A stroke occurs when blood supply to part of the brain is interrupted by a clot or bleeding.
The Stroke Foundation promotes the FAST warning signs:
- Face drooping
- Arm weakness
- Speech difficulty
- Time to call 000
While not all strokes cause unconsciousness, severe strokes — particularly those affecting the brainstem — may result in collapse or coma.
Stroke is a medical emergency. Immediate treatment improves survival and recovery outcomes.
Heart Attack: Cardiac Emergencies and Collapse
A heart attack occurs when blood flow to part of the heart muscle is blocked. According to the Heart Foundation, symptoms can include:
- Chest pressure, tightness or pain
- Pain spreading to arm, neck or jaw
- Shortness of breath
- Sweating
- Nausea
In some cases, a heart attack can trigger dangerous heart rhythms (cardiac arrest), causing sudden unconsciousness.
If a heart attack is suspected, call Triple Zero (000) immediately.
Asphyxia: Oxygen Deprivation
Asphyxia occurs when the body does not receive enough oxygen. Causes include:
- Choking
- Drowning
- Suffocation
- Severe asthma attack
- Smoke inhalation
The brain can begin to suffer irreversible damage after just a few minutes without oxygen. Loss of consciousness can occur rapidly if airflow is not restored.
Immediate emergency response and CPR may be required.
Poisons: Toxic Substances and Overdose
Poisoning can occur through ingestion, inhalation, injection, or skin contact. Substances may include:
- Medications (accidental or intentional overdose)
- Alcohol
- Illicit drugs
- Household chemicals
- Carbon monoxide
According to Healthdirect Australia, poisoning symptoms may include confusion, abnormal breathing, seizures, vomiting, and unconsciousness.
In Australia, suspected poisoning cases can also contact the Poisons Information Centre on 13 11 26 for urgent advice.
Epilepsy: Seizures and Loss of Awareness
Epilepsy is a neurological condition involving recurrent seizures.
Some seizures involve full loss of consciousness (generalised tonic-clonic seizures), while others may involve altered awareness.
The Healthdirect Australia notes that seizures lasting longer than five minutes require emergency medical assistance.
Proper diagnosis, medication management, and seizure action plans significantly reduce risk.
Diabetes: Blood Sugar Emergencies
Both low and high blood sugar levels can cause unconsciousness.
Hypoglycaemia (Low Blood Sugar)
According to Diabetes Australia, symptoms include:
- Sweating
- Shaking
- Confusion
- Drowsiness
- Collapse
Severe hypoglycaemia can lead to unconsciousness if not treated promptly with glucose.
Hyperglycaemia (High Blood Sugar)
Severely high blood sugar can lead to diabetic ketoacidosis (DKA) or hyperosmolar hyperglycaemic state (HHS), both of which may cause coma if untreated.
What To Do If Someone Is Unconscious in Australia
If a person is unconscious:
- Check for danger.
- Check response.
- Call 000 immediately.
- Open airway and check breathing.
- If breathing normally, place in the recovery position.
- If not breathing, begin CPR.
Australian first aid follows the DRSABCD action plan.
Final Thoughts: Recognising the FISHSHAPED Causes of Unconsciousness
The FISHSHAPED acronym is a practical tool to remember the major causes of fainting and unconsciousness in Australia — from common fainting episodes to life-threatening emergencies like stroke, heart attack, shock, or diabetic crisis.
Understanding the warning signs and responding quickly can save lives.
If you would like, I can now optimise this further for a specific audience (workplace first aid, schools, childcare, or community training).
Sources:
Better Health Channel. (n.d.). Heatstroke. Victorian Department of Health. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/heatstroke
Better Health Channel. (n.d.). Hypothermia. Victorian Department of Health. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/hypothermia
Better Health Channel. (n.d.). Shock. Victorian Department of Health. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/shock
Diabetes Australia. (n.d.). Hypos (hypoglycaemia). https://www.diabetesaustralia.com.au/living-with-diabetes/hypos/
Diabetes Australia. (n.d.). Hyperglycaemia. https://www.diabetesaustralia.com.au/living-with-diabetes/hyperglycaemia/
healthdirect Australia. (n.d.). Choking. https://www.healthdirect.gov.au/choking
healthdirect Australia. (n.d.). Epilepsy. https://www.healthdirect.gov.au/epilepsy
healthdirect Australia. (n.d.). Fainting. https://www.healthdirect.gov.au/fainting
healthdirect Australia. (n.d.). Head injury. https://www.healthdirect.gov.au/head-injury
healthdirect Australia. (n.d.). Poisoning. https://www.healthdirect.gov.au/poisoning
Heart Foundation. (n.d.). Heart attack. https://www.heartfoundation.org.au/your-heart/heart-attack
Stroke Foundation. (n.d.). Stroke symptoms. https://strokefoundation.org.au/About-Stroke/Stroke-symptoms