Electrocardiogram (EKG or ECG): Why It's Done, How to Prepare, What Happens and Results

Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: November 2026 · How we review

Quick Answer: What is an electrocardiogram (EKG)?

An electrocardiogram, also called an EKG or ECG, is a quick, noninvasive test that records your heart's electrical activity. Providers use it to find rhythm problems, check on heart conditions and see how well a treatment is working. A resting test takes about 10 minutes, the recording itself takes about 10 seconds, and you feel nothing while it runs. [1]

What the research says

• ECG changes in older adults can signal higher heart risk. In a study of 2,192 adults aged 70 to 79 with no known heart disease, 13% had minor and 23% had major ECG abnormalities at the start. Over 8 years, coronary heart disease events occurred at 17.2 per 1,000 person-years with a normal ECG, compared with 29.3 with minor and 31.6 with major abnormalities, even after accounting for traditional risk factors. (Auer et al., JAMA, 2012) [2]

• A normal EKG cannot rule out a thickened heart muscle. A review of 21 studies with 5,608 people with high blood pressure found that a negative EKG barely changed the chance of left ventricular hypertrophy, lowering it only from 33% to 31% in primary care. The authors concluded EKG criteria should not be used to rule out this condition. (Pewsner et al., The BMJ, 2007) [3]

Key takeaways

• An EKG is a quick, painless test that records your heart's electrical activity; it uses no radiation and does not send electricity into your body. [1]

• The standard test is a 12-lead EKG, with six electrodes on your chest and four on your limbs. [1]

• It can help find arrhythmias, poor blood flow to the heart, heart attacks, enlarged heart chambers, valve problems and heart failure. [1]

• You can eat and drink normally beforehand, but skip oily skin creams and lotions on the day of the test. [1]

• A standard EKG can miss rhythm problems that come and go, so your provider may suggest a longer-term monitor. [1]

What is an electrocardiogram?

An electrocardiogram records the electrical signals that make your heart beat. The terms EKG and ECG mean the same thing; "EKG" comes from the German spelling, which uses a "k." [1]

The test can be done in a provider's office, a hospital or even an ambulance. The standard version is a 12-lead EKG done in a medical facility. It records for a short time, usually while you are at rest, or while you exercise as part of a stress test. [1]

Some rhythm problems come and go, and a standard EKG may miss them. In those cases, your provider may use a longer-term recorder, such as a Holter monitor or an implantable loop recorder. [1]

Why would you need an EKG?

Symptoms and heart conditions both guide whether you need an EKG.

Your provider may order an EKG to: [1]

• Find the cause of your symptoms

• Diagnose a heart condition

• Check how your heart works after a pacemaker is placed

• See how well a new medication is working

• Check whether you are fit for an upcoming surgery

• Look at your heart health if you have a higher risk of heart disease

• Check your heart rhythm after a heart attack

Symptoms that may lead to an EKG

You may need an EKG if you have: [1]

• Chest pain

• Shortness of breath

• Tiredness

• Dizziness or fainting (syncope)

• Blue hands and feet (cyanosis)

• A fluttering, skipped or fast heartbeat

• Trouble getting enough blood supply during physical activity (chronotropic incompetence)

How do you prepare for an EKG?

You can eat and drink as you normally would before the test. A few simple steps help the electrodes stick well: [1]

Do	Avoid
Eat and drink normally	Oily or greasy skin creams and lotions on the day of the test
Wear a shirt that is easy to take off	Full-length pantyhose or tights that cover the leg electrode sites

Sources: [1]

What happens during an EKG?

A resting EKG takes about 10 minutes from start to finish.

A provider attaches 10 electrodes to your skin with sticky pads: six on your chest and four on your arms and legs. Together they record 12 views (leads) of your heart. They may shave small areas of hair so the pads make good contact. [1]

For a resting EKG, you lie flat and relax. For a stress test, you walk on a treadmill or pedal a stationary bike instead. [1]

A computer turns your heart's electrical signals into a wave pattern on paper or a screen. You do not feel anything during the recording. Afterward, the electrodes are removed and you can go back to your normal activities. [1]

Step	What to expect
Setup and resting test	About 10 minutes in total
Recording	About 10 seconds
Stress-test EKG	Takes longer than a resting test

Sources: [1]

Are there any risks?

An EKG is a low-risk test. It uses no radiation and does not send electricity into your skin. The sticky patches can sometimes irritate your skin. [1]

What do EKG results show?

Each wave on an EKG shows a different part of the heartbeat.

Your provider looks at the amount and strength of electrical activity and the timing between the waves. A normal EKG shows a regular, repeating pattern. [1]

Wave	What it looks like	What it shows
P wave	A small bump	Activity in the upper chambers (atria)
QRS complex	A spike	Activity in the lower chambers (ventricles)
T wave	A small bump	The heart resting or recovering

Sources: [1]

Regular spacing between the waves means your heart rhythm is regular. Unusual patterns can point to a problem and help show where in the heart it is. [1]

Conditions an EKG can help find

An EKG can help identify: [1]

• Arrhythmias or problems with how electrical signals travel through the heart

• Poor blood flow to the heart muscle (ischemia) from coronary artery disease

• Heart valve problems

• Congenital heart disease

• A heart attack

• Enlarged heart chambers

• Heart damage or heart failure

When will you get results?

In urgent cases, results may be available right away. Routine or pre-surgery tests can take a few days. Your records are kept so future EKGs can be compared with them. [1]

What happens if your EKG is abnormal?

If your results are abnormal, your provider may adjust your pacemaker settings, order other tests to confirm a diagnosis, or plan medications, procedures or surgery. [1]

Call your provider if several days pass with no word on your results, if your symptoms get worse than before the test, or if you have questions about next steps. [1]

Conclusion

An EKG is a quick, painless test that gives your provider a snapshot of your heart's rhythm and electrical activity. It helps explain symptoms such as chest pain, dizziness or a fluttering heartbeat.

A single EKG may not catch every problem. Ask your provider what your results mean and whether you need other tests, such as a longer-term heart monitor.

Keep learning: Read our guide to heart arrhythmia or our guide to STEMI heart attacks. You can also learn about the Holter monitor and the echocardiogram. For more trusted, doctor-reviewed health guides, visit Rinnit.com.

FAQ

What is an electrocardiogram?

It is a quick, noninvasive test that records your heart's electrical activity.

Is there a difference between an EKG and an ECG?

No. They are the same test; "EKG" comes from the German spelling.

Why would I need an EKG?

To find the cause of symptoms such as chest pain or dizziness, diagnose heart conditions or check how a treatment is working.

How long does an EKG take?

A resting EKG takes about 10 minutes, and the recording itself takes about 10 seconds.

Does an EKG hurt?

No. You feel nothing during the recording, though the sticky pads may irritate your skin.

How should I prepare for an EKG?

Eat and drink normally, skip oily skin lotions and wear a shirt that is easy to remove.

Is an EKG safe?

Yes. It is low risk, uses no radiation and does not send electricity into your body.

What can an EKG detect?

Arrhythmias, poor blood flow to the heart, heart attacks, enlarged heart chambers, valve problems and heart failure.

Can a normal EKG miss a heart problem?

Yes. Rhythm problems that come and go may be missed, so a longer-term monitor may be used.

How soon will I get my EKG results?

Urgent results may come right away; routine results can take a few days.

Related Reading

Cardiac Telemetry Monitoring: Real-Time Heart Rhythm Monitoring explains continuous heart rhythm monitoring in the hospital and at home.

Ambulatory Heart Monitors: Holter, Event, Patch and Loop Recorders compares the wearable and implantable monitors that record heart rhythm at home.

Heart Arrhythmia: Symptoms, Types, Causes, Diagnosis & Treatment — Complete Guide explains irregular heart rhythms, one of the main problems an EKG can find.

What Is Atrial Fibrillation (AFib)? Symptoms, Causes, and Treatment covers a common type of irregular heart rhythm and how it is treated.

What Is Tachycardia? A Plain-Language Guide to the Fast Heartbeat, Its Causes, and Its Treatment explains a fast heartbeat, one of the symptoms that may lead to an EKG.

Bradycardia: Slow Heart Rate, Symptoms, Causes, and Treatment describes a slow heart rate, its causes and how it is treated.

Heart Block: Understanding Types, Symptoms, and Treatment explains problems with how electrical signals travel through the heart.

Understanding STEMI: The Severe Heart Attack covers a severe type of heart attack, one of the conditions an EKG can help find.

NSTEMI Heart Attack: Essential Guide to Symptoms, Risks, and Recovery explains another type of heart attack and how it is managed.

References

1. Cleveland Clinic. Electrocardiogram (EKG or ECG Test). Cleveland Clinic. Last updated February 9, 2026. https://my.clevelandclinic.org/health/diagnostics/16953-electrocardiogram-ekg

2. Auer R, Bauer DC, Marques-Vidal P, et al. Association of major and minor ECG abnormalities with coronary heart disease events. JAMA. 2012;307(14):1497-1505. PMID 22496264. https://doi.org/10.1001/jama.2012.434

3. Pewsner D, Jüni P, Egger M, et al. Accuracy of electrocardiography in diagnosis of left ventricular hypertrophy in arterial hypertension: systematic review. BMJ. 2007;335(7622):711. PMID 17726091. https://doi.org/10.1136/bmj.39276.636354.AE

Medical disclaimer

This article is for general education only and does not replace advice from a qualified healthcare professional. Talk to your doctor about your own diagnosis and treatment, and seek emergency care right away for severe or sudden symptoms.