Basic life support, often shortened to BLS, is the immediate care given to someone whose breathing or circulation has failed. It includes recognising cardiac arrest, calling 999, starting CPR and using an automated external defibrillator (AED) as quickly as possible.

These are practical emergency skills that can help keep oxygenated blood moving around the body until professional medical help arrives.

You do not need to be a healthcare professional to learn basic life support. CPR and AED skills can be learned by members of the public, workplace first aiders, parents, carers and people who may need to respond to an emergency.

What Does BLS Mean?

BLS stands for Basic Life Support.

In simple terms, basic life support describes the immediate actions used to support a casualty’s airway, breathing and circulation during a life-threatening emergency.

For an adult in cardiac arrest, the priorities include:

recognising that something is seriously wrong
calling 999
recognising absent or abnormal breathing
starting chest compressions
providing rescue breaths if trained and able
using an AED as soon as one is available
continuing CPR and following the AED until professional help takes over

These actions form an important part of the response to cardiac arrest.

Is Basic Life Support the Same as CPR?

Not quite.

CPR is part of basic life support, but BLS is broader than CPR alone.

CPR refers to cardiopulmonary resuscitation. It uses chest compressions and, where appropriate, rescue breaths to help maintain blood flow and oxygen delivery when someone is in cardiac arrest.

Basic life support includes the wider emergency response around CPR.

That means recognising cardiac arrest, summoning emergency help and using an AED are also important parts of BLS.

Our Seven Steps of CPR guide looks specifically at how CPR is performed.

Why Is Basic Life Support Important?

When the heart stops effectively pumping blood around the body, the brain and other vital organs are deprived of oxygen.

Immediate action matters.

Resuscitation Council UK states that bystander CPR and early use of an AED can increase the chances of survival following an out-of-hospital cardiac arrest.

The person standing nearby when someone collapses may therefore have an extremely important role.

You do not have to diagnose exactly what has happened before calling for help.

The priority is to recognise an emergency, call 999 and act.

Basic Life Support: What Should You Do?

Current Resuscitation Council UK guidance provides a simple community approach:

Check. Call. CPR.

If someone appears to be unresponsive:

Make sure it is safe to approach.
Check whether they respond.
Call 999 if they are unresponsive.
Assess their breathing while waiting for the call to be answered.
If they are unresponsive and not breathing normally, start CPR.
Use an AED as soon as one becomes available.
Continue following the AED and ambulance service instructions.

The ambulance call handler can help you recognise cardiac arrest and talk you through CPR if necessary.

Step 1: Check for Danger and Response

Before approaching a collapsed person, make sure you are not putting yourself or anyone else in danger.

Look for obvious hazards such as:

traffic
electricity
machinery
fire
falling objects
violence
other environmental dangers

Once it is safe, check whether the casualty responds.

Speak loudly to them and gently try to get a response.

If they are unresponsive, get help immediately.

Step 2: Call 999

This is an important part of the current basic life support sequence.

If an adult is unresponsive, call 999 without delay.

If someone else is present, ask them to make the call. If you are alone, call yourself and use speakerphone where possible.

Current Resuscitation Council UK guidance changed in 2025. Rescuers no longer need to establish that the casualty is not breathing normally before making the emergency call.

Instead, call 999 when you identify that the person is unresponsive and then assess their breathing while waiting for the call to be answered.

The ambulance service call handler can help you decide whether the casualty is in cardiac arrest.

Step 3: Check Their Breathing

Assess whether the casualty is breathing normally.

One of the difficulties with cardiac arrest is that the casualty may still make occasional gasps or unusual breathing movements.

These can include:

slow, laboured breathing
gasping
panting
irregular or abnormal breaths

These are not necessarily normal breathing.

Agonal gasps can occur during cardiac arrest and should not be mistaken for a sign that the casualty is breathing adequately.

If someone is unresponsive and their breathing is absent or abnormal, assume cardiac arrest and start CPR.

If you are unsure, the ambulance service call handler can help you.

Step 4: Start Chest Compressions

Place the casualty on their back and start chest compressions as quickly as possible.

For an adult:

place the heel of one hand on the lower half of the breastbone, in the centre of the chest
place your other hand on top
interlock your fingers
keep your arms straight
position your shoulders above the casualty’s chest
compress the chest 5 to 6 cm
aim for 100 to 120 compressions per minute
allow the chest to fully recoil after each compression
keep interruptions to an absolute minimum

Good-quality chest compressions help maintain blood flow to the brain and other vital organs.

Do You Have to Give Rescue Breaths?

If you have been trained and are able to provide rescue breaths, use:

30 chest compressions followed by 2 rescue breaths.

Each rescue breath should contain enough air to make the casualty’s chest start to rise.

Avoid blowing excessive amounts of air into the casualty.

If you are not trained or are unable to give rescue breaths, perform continuous chest compressions.

Doing something is far better than doing nothing.

The ambulance service call handler can guide an untrained rescuer through chest-compression-only CPR.

Step 5: Use an AED

An automated external defibrillator, or AED, analyses the casualty’s heart rhythm and determines whether an electrical shock is required.

Anyone can use an AED.

You do not need specialist training before using one in an emergency.

When the AED arrives:

Switch it on.
Expose the casualty’s chest.
Attach the pads as shown on the device.
Follow the spoken and visual instructions.
Make sure nobody touches the casualty while the AED analyses the heart rhythm.
Deliver a shock if instructed.
Immediately resume CPR when instructed.
Continue following the AED prompts.

If the AED says that a shock is not required, this does not mean you should stop.

Resume CPR immediately and continue following the AED.

Our guide to how to use an AED explains the process in more detail.

You can also read our complete guide explaining what an automated external defibrillator is.

Why Is an AED Part of Basic Life Support?

CPR and defibrillation perform different jobs.

CPR helps maintain some circulation of oxygenated blood.

An AED can deliver an electrical shock when it identifies a shockable heart rhythm.

CPR does not replace defibrillation, and an AED does not replace CPR.

They work together as part of the emergency response to cardiac arrest.

This is why early access to an AED is so important.

Can Anyone Use a Defibrillator?

Yes.

Resuscitation Council UK states that anyone can use an AED.

Modern AEDs provide clear voice and visual instructions and analyse the casualty’s heart rhythm automatically.

The machine determines whether a shock is appropriate.

It will not simply deliver a shock because somebody has attached the pads.

If you are with someone in suspected cardiac arrest and an AED is available, use it.

Do not wait for someone who has received formal AED training to arrive.

Where Can You Find an AED?

AEDs can now be found in many locations, including:

workplaces
schools
leisure centres
supermarkets
community buildings
railway stations
sports facilities
public spaces

During a 999 call, the ambulance service may be able to direct you to a nearby registered AED.

Public access defibrillators registered with The Circuit, the UK’s national defibrillator network, can be identified by ambulance services.

Our guide to AED placement explains where organisations should consider locating their equipment.

What Is the Chain of Survival?

The Chain of Survival describes the actions that together improve the chances of surviving cardiac arrest.

These include:

early recognition of cardiac arrest and calling for help
early CPR
early defibrillation
advanced resuscitation and post-resuscitation care

A bystander cannot provide every part of this chain.

However, the first few links can begin before an ambulance arrives.

Recognising cardiac arrest, calling 999, performing CPR and using an AED can all be started by people at the scene.

What Is the Difference Between BLS and First Aid?

There is considerable overlap, but they are not exactly the same thing.

First aid covers a much wider range of illnesses and injuries.

This can include:

bleeding
burns
choking
fractures
seizures
asthma
anaphylaxis
shock
head injuries
poisoning
unconscious casualties
cardiac arrest

Basic life support concentrates particularly on the immediate actions required when a person’s breathing or circulation has failed.

BLS therefore forms an important part of first aid training, but first aid extends considerably beyond BLS.

Is BLS the Same as Advanced Life Support?

No.

Basic Life Support (BLS) involves immediate lifesaving interventions such as CPR and early defibrillation.

Advanced Life Support (ALS) is different.

ALS involves more advanced clinical assessment, equipment, medication, airway management and treatment performed by appropriately trained healthcare professionals.

A workplace first aider or member of the public is not expected to provide advanced life support.

Their role is to recognise the emergency, summon professional help and provide appropriate immediate care.

Does BLS Include Choking?

Airway obstruction is closely connected with basic life support and resuscitation training.

A severe choking incident can prevent oxygen reaching the lungs and can eventually cause the casualty to become unresponsive.

If this happens, CPR may become necessary.

Our choking first aid guide explains how to recognise choking and what to do for a conscious or unresponsive casualty.

Does BLS Include the Recovery Position?

An unresponsive casualty who is breathing normally does not need CPR.

They will usually need their airway protected and their condition continuously monitored while waiting for emergency help.

The recovery position may be appropriate depending on the circumstances and injuries involved.

The important distinction is:

Unresponsive + breathing normally = protect the airway and monitor.

Unresponsive + absent or abnormal breathing = cardiac arrest, start CPR.

If there is any doubt about whether breathing is normal, follow the instructions of the ambulance service call handler.

What Is Basic Life Support (BLS) CPR, AEDs and Emergency Response

Is Basic Life Support Different for Babies and Children?

Yes, there are important differences.

Paediatric cardiac arrest is more commonly associated with breathing problems than adult cardiac arrest, so rescue breaths have particular importance.

Paediatric CPR also uses different techniques depending on the child’s age and size.

For babies and children, trained rescuers begin with five initial rescue breaths before continuing CPR.

We have created a separate guide to child and baby CPR because these differences deserve to be explained properly rather than squeezed into adult BLS instructions.

People responsible for babies and children should also consider practical Paediatric First Aid training.

Can CPR Cause an Injury?

People sometimes hesitate because they are frightened of hurting the casualty.

This should not stop you performing CPR on someone you believe is in cardiac arrest.

Chest compressions are forceful and injuries can occur during resuscitation.

However, a person in cardiac arrest needs immediate treatment.

Resuscitation Council UK emphasises that the risk of serious harm from CPR is low and rescuers should not be afraid to act when cardiac arrest is suspected.

If you are uncertain, call 999 and follow the ambulance service’s instructions.

Do You Need BLS Training to Perform CPR?

No.

If somebody is in cardiac arrest, you should not withhold CPR simply because you have never attended a course.

Call 999.

The ambulance service call handler can provide instructions.

However, practical basic life support training gives you an opportunity to learn and physically practise the skills before you are faced with a real emergency.

Training allows learners to practise:

recognising cardiac arrest
checking responsiveness
recognising abnormal breathing
calling for emergency assistance
chest compressions
rescue breaths
using an AED
responding as part of a team

It also allows an instructor to correct technique and answer questions.

That practical experience can make it much easier to act confidently when something genuinely goes wrong.

Is Basic Life Support Included in Workplace First Aid Courses?

Yes.

CPR and AED use are fundamental practical skills within workplace first aid training.

Depending on your role and workplace requirements, appropriate training might include:

Employers should select first aid provision based on an appropriate assessment of their workplace needs rather than simply choosing a course by name.

Our guide explaining what first aid course you need can help you understand the different options.

Basic Life Support: What Should You Remember?

The most important basic life support actions are straightforward:

CHECK

Make sure it is safe and check whether the casualty responds.

CALL

If they are unresponsive, call 999 immediately.

ASSESS BREATHING

If they are unresponsive and not breathing normally, assume cardiac arrest.

START CPR

Begin chest compressions as quickly as possible.

For a trained rescuer providing rescue breaths, use 30 compressions to 2 breaths.

USE AN AED

Attach an AED as soon as one becomes available and follow its instructions.

KEEP GOING

Continue CPR and follow the AED and ambulance service instructions until professional help takes over or the casualty shows clear signs of life.

Learn Basic Life Support Practically

You can learn the principles of basic life support from an article, but CPR and AED use are practical skills.

First Aid and Safety Training teaches CPR, AED use and emergency response as part of our practical first aid courses.

We provide training for individuals and organisations across the North East, with courses at our training centre and onsite training for businesses and other organisations.

Explore our first aid training across the North East or contact First Aid and Safety Training to discuss the right training for you or your organisation.

You can also see our South Shields training location and customer reviews on Google Maps.

Real Skills, Real Confidence.