QT Interval (Corrected)
This test measures the corrected QT interval, a key part of an electrocardiogram (ECG) that helps assess heart rhythm and potential risks for abnormal heartbeats.
["The corrected QT interval helps identify irregular heart rhythms that may require medical attention."]
Key facts at a glance
- LOINC
- 18539-7
- Short code
- Q-T interval L-V2
- Synonyms
- Q-T interval L-V2
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ekg
- 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 the QT Interval?
The QT interval represents the time it takes for an electrical signal to travel through your heart’s ventricles. A prolonged QT interval can increase the risk of dangerous heart rhythms, such as torsades de pointes, which may lead to fainting or sudden cardiac arrest. Your doctor may order this test if they suspect heart rhythm issues, electrolyte imbalances, or other conditions affecting heart function.
Why Might You Need This Test?
Your healthcare provider may recommend a corrected QT interval test if you have symptoms like fainting, dizziness, or palpitations; a family history of heart rhythm disorders; certain medications that affect heart rhythm; or conditions like heart disease, low potassium, or heart failure. It’s also sometimes checked during routine evaluations for people at higher risk.
How Is the Test Performed?
This test is done through an electrocardiogram (ECG), a simple, painless procedure where electrodes are placed on your chest. The electrodes detect your heart’s electrical activity and record the timing of your heartbeats. No special preparation is needed, but you may be asked to avoid caffeine or nicotine before the test.
What Does the Result Mean?
Results are interpreted by your doctor based on your overall health, medications, and symptoms. A prolonged corrected QT interval may signal a need for further evaluation, including additional tests or adjustments to your treatment plan. A normal result doesn’t rule out all heart rhythm concerns, so follow-up may still be recommended.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance: The corrected QT interval is crucial for detecting genetic or acquired conditions that can disrupt heart rhythm. Prolonged intervals may indicate electrolyte imbalances (e.g., low potassium or magnesium), certain medications, or structural heart issues. Early identification allows for timely interventions to prevent serious complications.
Short name
QTc Interval
Frequently asked questions
What causes a prolonged QT interval?
What should I do if my QT interval is abnormal?
Can I prevent a prolonged QT interval?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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