How to use an AED on an adult
Turn the AED on and do what it says. Every AED talks you through the same steps: attach the pads, stand clear for the analysis, shock if it advises one, and go back to CPR.
- Check the person and call 911. If they don’t respond and aren’t breathing normally, or are only gasping, call 911 (or have someone call) and send someone for the AED.
- Start CPR right away while the AED is on its way: push hard and fast in the center of the chest.
- Turn on the AED as soon as it arrives, and follow its voice prompts.
- Bare the chest. Remove or cut away clothing over the chest, and wipe the skin dry if it’s wet.
- Attach the pads where the pictures on the pads show, and plug the pad cable into the AED if it isn’t already connected.
- Stand clear while it analyzes. Make sure nobody is touching the person, and say “Clear!” out loud.
- Shock if the AED advises it. Check again that nobody is touching the person, then press the shock button. A fully automatic AED counts down and shocks by itself.
- Restart CPR right away, starting with compressions, after a shock or if no shock is advised. Keep following the prompts until EMS takes over or the person starts to move or breathe normally.
These steps follow the American Heart Association’s 2025 lay rescuer steps and the American Red Cross’s AED steps, which the Red Cross applies to adults and to children 8 or older who weigh more than 55 pounds. Stop compressions only when the AED tells you to, so it can analyze or shock. After a shock, don’t pause to check for a pulse: the AHA’s 2025 guidelines say to restart compressions immediately and keep the pauses around the shock as short as possible. The AED checks the rhythm again about every 2 minutes and tells you what to do.
Pad position matters less than speed. The Red Cross notes that if the two pads end up swapped, the AED still works. Our guide to AED pad placement shows both standard positions and what to do about hair, water and implants.
Before the AED arrives: call 911 and start CPR
If someone collapses and isn’t breathing normally, call 911 and start CPR at once. Send someone else for the AED if you can; if you’re alone with an adult, call first, then start CPR.
The AHA’s steps for an adult: call for help, have someone bring the AED and start compressions. If you’re alone and have a phone, put 911 on speaker so you can start CPR while you talk. If two people are there, one starts CPR while the other calls and fetches the AED. Alone without a phone, the AHA says to call 911 and get a nearby AED yourself, then start CPR.
For adult compressions, the AHA’s 2025 guidelines say:
- Place the heel of your hand in the middle of the chest, on the lower half of the breastbone, with your other hand on top.
- Push at least 2 inches (5 cm) deep but not more than 2.4 inches (6 cm), and let the chest come all the way back up after each push.
- Keep a rate of 100 to 120 compressions a minute.
- Kneel beside a person on a firm surface, with their chest at about the level of your knees.
If others are there, take turns on compressions about every 2 minutes, or sooner if you tire. A short burst of CPR while someone opens the AED and gets the pads ready is fine; the AHA says to keep CPR going until the AED is applied.
Using an AED on a child or infant
Use the AED on a child or infant in cardiac arrest, with child pads or the AED’s child setting if it has one. If it doesn’t, use the adult pads: both the AHA and the Red Cross say an adult AED can still save a child.
The AHA’s 2025 guidelines recommend attaching an AED as soon as possible, with a pediatric attenuator for infants and children under 8. The attenuator lowers the shock energy and comes as child pads, a key or a switch, depending on the AED. The Red Cross puts the line at children 8 or younger, or 55 pounds (25 kg) or less, and says to follow the pad diagram on the AED. Never use child pads or a child setting on an adult: the shock would be too weak.
When you start depends on what happened. For a child or infant who collapses suddenly in front of you, the AHA says to call for help and get the AED right away. If you didn’t see the collapse and you’re alone, give about 2 minutes of CPR first, then call 911 and get the AED. Push about one-third of the depth of the chest: about 2 inches (5 cm) for a child and 1.5 inches (4 cm) for an infant.
On a small chest, the pads must not touch. If they would, center one pad on the chest, then center the second pad on the back. Our guide to pediatric AED pads covers ages, pads by AED model and placement on infants.
Special situations
Most things that seem like obstacles don’t stop you using an AED. Get the person out of water, dry the chest, keep the pads off any implanted device, metal jewelry or medication patch, and carry on.
- Water, rain and snow: move the person out of any water before using the AED. The Red Cross says AEDs are safe to use in rain or snow; keep the AED itself out of the wet, and dry the person’s chest. Don’t use an alcohol wipe, because alcohol is flammable.
- Drowning: the AHA says to begin CPR with breaths before you attach the AED, then use it as usual.
- Metal surfaces: the Red Cross says it’s safe to shock someone lying on metal as long as the pads don’t touch the metal and nobody touches the person during the shock.
- Pacemakers and implanted defibrillators: often seen or felt as a lump below the collarbone. Don’t put a pad right over it; move the pad aside.
- Medication patches: take off any patch where a pad will go, wearing gloves so the drug doesn’t get on your skin.
- Chest hair: it rarely stops the pads from sticking. If it’s very thick, quickly shave just the pad areas with the razor in the AED’s rescue kit.
- Jewelry, piercings and bras: don’t delay to remove jewelry; keep the pads off metal. The AHA’s 2025 guidelines say it may be reasonable to move a bra aside rather than take it off, as long as the pads go on bare skin. If it still gets in the way, remove it.
- Pregnancy: the Red Cross says AEDs are safe to use on a pregnant person, with adult pads.
- Oxygen and fuel: don’t use the AED near flammable materials such as gasoline or free-flowing oxygen.
After the AED is used
If the person starts breathing or moving, stop CPR but leave the pads on and the AED switched on, and stay with them until EMS takes over. Afterward the AED needs new pads before it goes back in service.
The Red Cross says to keep the pads on even when there’s an obvious sign of life, because the heart can stop again and the AED needs to be ready. When EMS arrives, tell them what happened, how long CPR went on and how many shocks the AED gave. Many AEDs store the event, and EMS or your medical director may ask for that data.
Then get the AED ready for next time:
- Replace the pads. They are single-use, even if no shock was given.
- Check the battery and the status indicator, and replace the battery if the AED asks.
- Restock the rescue kit: gloves, razor, scissors and CPR mask.
- Report the use where your state requires it. Some state AED laws require reporting each use to EMS, a physician or a state agency.
- Write down what happened while it’s fresh, and talk it through with the people who responded.
AED Log keeps an AED incident report for each use, with shocks, CPR, EMS and outcome, and flags the pads for replacement.
Getting trained
You don’t need training to use an AED in an emergency, but a short CPR and AED course makes you faster and more confident. Workplaces that must have trained responders usually need a course with a hands-on skills check.
The American Heart Association’s Heartsaver CPR AED and the American Red Cross’s Adult CPR/AED courses teach lay rescuers to use an AED on a practice trainer. Both offer an online part followed by a hands-on session. The Red Cross notes that its online-only course doesn’t meet OSHA’s requirements for workplace certification, so check what your employer or state asks for. See our AED cost guide for course prices.
Cards usually last 2 years. Our guide to CPR and AED certification explains how long each card lasts, and AED Log tracks every responder’s certification with a reminder before it expires.
How to use an AED FAQ
Should you call 911 or start CPR first?
Both, as fast as you can. If someone is with you, one person starts CPR while the other calls 911 and gets the AED. Alone with an adult, the AHA says to call 911 first, on speaker if you can, then start CPR.
What does “no shock advised” mean?
The AED found a heart rhythm a shock can’t fix, or the person isn’t in cardiac arrest. Restart CPR right away if they aren’t breathing normally, and leave the pads on: the AED checks again about every 2 minutes.
Can an AED shock the person using it?
Not if nobody touches the patient during the analysis and the shock. The AED tells everyone to stand clear; say “Clear!” out loud and check before you press the shock button.
When do you stop CPR when using an AED?
Pause only when the AED tells you to, for its analysis or a shock, then restart compressions right away. Keep going until EMS takes over or the person starts to move or breathe normally.
Can you use an AED on someone who is wet or in the rain?
Yes, once they’re out of any water. The Red Cross says AEDs are safe to use in rain or snow: keep the AED dry, wipe the chest dry, and don’t use an alcohol wipe, because alcohol is flammable.