Corrected QT Interval (Fridericia Formula)
This test measures the duration of the QT interval on your heart’s electrical tracing, adjusted for heart rate using the Fridericia method. It helps assess potential risks for abnormal heart rhythms.
["The corrected QT interval helps identify heart rhythm irregularities that may require medical attention."]
Key facts at a glance
- LOINC
- 76634-5
- Short code
- Q-T interval corrected Fridericia
- Synonyms
- Q-T interval corrected Fridericia
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- fridericia-formula
- 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 your heart’s electrical signals to fully contract and relax its ventricles. A prolonged QT interval may increase the risk of dangerous heart rhythms, such as torsades de pointes, which can be life-threatening. The Fridericia formula adjusts this measurement for heart rate to provide a more accurate comparison across different heartbeats.
Why Is This Test Done?
Your doctor may order this test if you have symptoms like fainting, seizures, or irregular heartbeat, or if you have conditions like heart disease, electrolyte imbalances, or certain medications that can affect heart rhythm. It’s also used to monitor people with a history of QT prolongation.
How Is This Test Performed?
This test is typically performed using an electrocardiogram (ECG), a simple, painless procedure where electrodes are placed on your chest. The ECG records your heart’s electrical activity over time. The corrected QT interval is calculated from this tracing using the Fridericia formula, which accounts for heart rate variations.
What Does the Result Mean?
Results are not provided with specific numeric ranges, as they depend on individual health factors. A prolonged corrected QT interval may signal an increased risk for abnormal heart rhythms, prompting further evaluation by your healthcare provider.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
QTc (Fridericia)
Frequently asked questions
Why might my doctor ask for this test?
What if my result is abnormal?
How often should I get this test?
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