EMG (Electromyography): What It Tests, What to Expect and Results

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

Quick Answer: What is an EMG test?

An EMG (electromyography) is a test that checks the health of the skeletal muscles and the nerves that control them. A thin needle electrode records the muscles' electrical activity at rest and when you tighten them. It helps diagnose carpal tunnel syndrome, pinched nerves, peripheral neuropathy, muscle diseases and ALS. The test usually takes 60 to 90 minutes. [1]

What the research says

• EMG and nerve studies are highly sensitive for carpal tunnel syndrome. A meta-analysis of 12 studies found that EMG with nerve conduction studies correctly identified 89% of people with carpal tunnel syndrome, with a specificity of 77%; ultrasound could not yet replace them. (Zaki et al., Cureus, 2022) [2]

• Bleeding after needle EMG on blood thinners is uncommon and mostly minor. In 58 people taking newer oral anticoagulants or warfarin, only 9 of 267 tested muscles (3.3%) had bleeding complications, and risk did not differ between the two drug types. (Nagarajan et al., Journal of Clinical Neurophysiology, 2021) [3]

Key takeaways

• EMG checks how your muscles and the motor nerves that control them work. [1]

• A nerve conduction study is often done right before the needle EMG. [1]

• Skip lotions and creams on test day, and tell your provider about blood thinners or a pacemaker. [1]

• The test usually takes 60 to 90 minutes and can be mildly uncomfortable. [1]

• Results usually come back within 24 to 48 hours and are read with other tests. [1]

What is an EMG?

Electromyography is a diagnostic test that evaluates your skeletal muscles and the nerves that control them. It is one type of electrodiagnostic testing. [1]

Motor nerves carry electrical signals from your brain and spinal cord to your muscles. An EMG can find problems in those nerves, in the muscles themselves or in how the two communicate. It measures how your muscles respond to electrical signals and how much electrical activity they make when they contract. [1]

What is a nerve conduction study?

Neurologists often perform a nerve conduction study (NCS) along with an EMG, usually right before it. An NCS measures the electrical signal traveling through a nerve before it reaches a muscle. Sticker-like surface electrodes are placed on your skin, and a small electrical impulse that feels like a quick shock is sent through the nerve while the response is recorded. Several nerves are usually tested. [1]

Why would you need an EMG?

EMG helps find where a nerve or muscle problem is.

Your provider may order an EMG if you have muscle weakness, numbness or tingling. It helps diagnose or rule out many conditions: [1]

Problem area	Examples
Peripheral nerves	Peripheral neuropathy and nerve compression, such as carpal tunnel syndrome
Nerve roots	Pinched nerves, cervical radiculopathy and sciatica
Muscles (myopathies)	Muscular dystrophy, polymyositis and dermatomyositis
Motor neurons	ALS and post-polio syndrome
Nerve-muscle connection	Myasthenia gravis

Sources: [1]

EMG is usually used together with other tests, such as imaging, blood tests or a muscle biopsy. [1]

How do you prepare for an EMG?

Simple steps help your EMG give accurate results.

• Bathe or shower before the test, and wear loose, comfortable clothing

• Do not put cream, lotion or perfume on your skin, because they can affect accuracy

• Tell your provider if you take a blood thinner such as warfarin, but do not stop it without talking to the provider who prescribed it

• Tell your provider if you have a pacemaker or another electrical medical device

• Your provider may ask you to avoid smoking and caffeine, such as coffee and tea, for 2 to 3 hours before the test

Sources: [1]

What happens during an EMG?

The needle only records; it does not send electricity.

You sit or lie down while your provider finds the muscles to test. A thin needle with an electrode goes through your skin into a muscle and stays there while that muscle is checked, which takes about 1 to 2 minutes per muscle. [1]

You relax the muscle and then tighten it at set times, such as by lifting or bending a limb. A machine shows the muscle's electrical activity on a screen and plays it as sound. The needle does not send electricity into your body; it only records, like a microphone. [1]

How long does an EMG take?

Usually 60 to 90 minutes, depending on how many muscles are tested. [1]

Does an EMG hurt?

You may feel some pain or discomfort when the needle goes in, but most people complete the test without problems. [1]

What happens after an EMG?

Tested muscles may feel tender for a few days, and you may see small bruises where the needles went in. The soreness is usually mild and improves within a week. [1]

Are there risks?

EMG is generally safe and complications are rare. Some people bleed afterward, especially if they take blood thinners. [1]

What do EMG results mean?

Results are usually available within 24 to 48 hours. An EMG alone usually does not give a diagnosis; your provider reads it with your symptoms and other tests. [1]

A damaged muscle may show abnormal electrical activity at rest and abnormal wave patterns when it contracts. EMG helps show whether a nerve or muscle problem is present, where it is and how extensive it is, and it can also help rule conditions out. [1]

When should you call your provider?

Contact your provider after an EMG if you have bleeding that will not stop, severe pain or tenderness where the needles went in, or redness, warmth, swelling or fever, which could signal an infection. [1]

Conclusion

An EMG gives your provider a direct look at how your muscles and motor nerves are working, which helps pinpoint the cause of weakness, numbness or tingling. It can be a little uncomfortable, but it is safe and usually finished in about an hour or so.

Prepare by skipping lotions, mentioning any blood thinners or devices, and ask your provider how the results fit with your other tests.

Keep learning: Read our guide to carpal tunnel syndrome or our guide to peripheral neuropathy. For more background, see the MedlinePlus page on electromyography.

FAQ

What is an EMG test?

A test that records the electrical activity of your muscles to check the health of muscles and the nerves that control them. [1]

What conditions can an EMG diagnose?

Carpal tunnel syndrome, peripheral neuropathy, pinched nerves, sciatica, muscular dystrophy, polymyositis, ALS and myasthenia gravis, among others. [1]

What is the difference between EMG and a nerve conduction study?

EMG records muscle activity with a needle electrode, while a nerve conduction study uses skin electrodes and small shocks to measure nerve signals. [1]

How do I prepare for an EMG?

Shower, skip creams and lotions, wear loose clothing, and tell your provider about blood thinners or a pacemaker. [1]

Does an EMG hurt?

The needle can cause some pain or discomfort, but most people finish without problems. [1]

How long does an EMG take?

Usually 60 to 90 minutes. [1]

Can I take blood thinners before an EMG?

Tell your provider, but do not stop the medicine without talking to the provider who prescribed it. [1]

Will I be sore after an EMG?

Muscles may be tender and bruised for a few days, usually improving within a week. [1]

How long do EMG results take?

Usually 24 to 48 hours. [1]

When should I call a provider after an EMG?

If you have bleeding that won't stop, severe pain, or redness, warmth, swelling or fever at the needle sites. [1]

Related Reading

Nerve Conduction Study: What It Is, Procedure and Results explains how nerve conduction studies test nerve function.

Spurling Test: Checking for a Pinched Nerve in the Neck explains the neck exam test for a pinched nerve.

Muscle Biopsy: Diagnosing Muscle Diseases, Procedure and Recovery explains the procedure that takes a small muscle sample to diagnose muscle diseases.

Evoked Potential Test: VEP, BAER and SSEP for MS and Nerve Problems explains the nerve-signal tests that include VEP, BAER and SSEP.

Carpal Tunnel Syndrome: Symptoms, Causes, Diagnosis and Treatment covers the most common nerve compression EMG helps confirm.

Peripheral Neuropathy: Symptoms, Causes, and Treatment Options Explained explains nerve damage that EMG and nerve studies can detect.

Radiculopathy (Pinched Nerve): Symptoms, Causes, Types, and Treatment describes nerve root problems EMG helps locate.

Sciatica: Complete Guide to Symptoms, Causes, Diagnosis, and Treatment covers a nerve root problem that EMG can help evaluate.

Amyotrophic Lateral Sclerosis (ALS): The Complete Guide explains a motor neuron disease where EMG is a key test.

Myasthenia Gravis: Symptoms, Causes, Diagnosis and Treatment covers a nerve-muscle junction disorder EMG helps diagnose.

What Is Muscular Dystrophy? A Plain-Language Guide to the Group of Diseases That Weaken Muscles describes muscle diseases that show changes on EMG.

References

1. Cleveland Clinic. EMG (Electromyography): What It Is, Purpose, Procedure & Results. Cleveland Clinic. Last updated February 10, 2023. https://my.clevelandclinic.org/health/diagnostics/4825-emg-electromyography

2. Zaki HA, Shaban E, Salem W, et al. A Comparative Analysis Between Ultrasound and Electromyographic and Nerve Conduction Studies in Diagnosing Carpal Tunnel Syndrome (CTS): A Systematic Review and Meta-Analysis. Cureus. 2022;14(10):e30476. PMID 36415360. https://doi.org/10.7759/cureus.30476

3. Nagarajan E, Dyer N, Bailey E, et al. Hematoma Risk After Needle Electromyography in Patients Using Newer Oral Anticoagulants. J Clin Neurophysiol. 2021;38(1):69-72. PMID 31725032. https://doi.org/10.1097/WNP.0000000000000643

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.