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Electroencephalogram (EEG) Study

Published: August 9, 2026Updated: August 16, 2026

An EEG measures the electrical activity in your brain using small sensors placed on your scalp. It helps diagnose conditions like epilepsy, brain injuries, or other neurological issues.

Quick summary

["EEGs detect abnormal brain wave patterns that may signal neurological problems."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
11523-8
Short code
EEG study
Synonyms
EEG study
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What Is an EEG Used For?

EEGs are primarily used to identify and monitor conditions affecting brain function, such as seizures, sleep disorders, or brain injuries. They can also help rule out other causes of symptoms like headaches, dizziness, or unexplained falls.

How Is an EEG Performed?

During an EEG, you’ll lie down with electrodes attached to your scalp. These electrodes detect electrical signals from your brain. You may be asked to stay still, focus on lights or sounds, or experience normal sleep patterns to capture different brain activity patterns.

Preparation for an EEG

No special preparation is needed for most EEGs, but you may be asked to avoid caffeine or alcohol before the test. If you’re having a sleep study, you’ll likely stay overnight in a monitoring room with electrodes attached to your head.

What to Expect During the Test

The procedure is painless but may feel uncomfortable due to the electrodes. You might hear beeping or buzzing sounds from the equipment. If you’re having a seizure study, you may experience a seizure while under observation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

EEG

Frequently asked questions

Why might my doctor order an EEG?
Your doctor may recommend an EEG if you have symptoms like unexplained seizures, frequent headaches, memory problems, or neurological symptoms like weakness, numbness, or vision changes. It can also be used to monitor conditions like epilepsy or brain tumors.
How long does an EEG take?
A standard EEG typically takes about 30 to 60 minutes, but a more detailed or sleep study may last several hours or overnight.
Can I drive or operate machinery after an EEG?
Yes, you can usually drive or operate machinery after an EEG unless you had a seizure or other event that required special monitoring. Always follow your doctor’s instructions.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy