Free Digoxin Concentration in Serum/Plasma
This test measures the amount of free (unbound) digoxin in your blood, which is the active form that affects your heart. Digoxin is a medication used to manage certain heart conditions.
["Free digoxin levels help doctors monitor how your heart responds to this medication safely."]
Key facts at a glance
- LOINC
- 3562-6
- Short code
- Digoxin Free SerPl-mCnc
- Synonyms
- Digoxin Free SerPl-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0.5
- Ref high
- 2
- Critical range
- — – 4 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
Why This Test Matters for Your Health
Digoxin is a heart medication that helps control your heartbeat, but too much can be harmful. Free digoxin levels ensure only the active part of the drug is present in your bloodstream, reducing risks of side effects like irregular heart rhythms.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before your blood draw if instructed by your provider. Wear a loose shirt for easy access to your arm.
How the Test Works
A healthcare professional will draw blood from a vein in your arm. The sample is then analyzed to measure the free (unbound) digoxin concentration using a sensitive lab method.
What the Results Mean
Results are compared to your individual target range, which your doctor determines based on your health, medication dose, and other factors. Abnormal levels may indicate whether your dose needs adjustment.
Reference range
Therapeutic: 0.5-2.0 ng/mLN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free digoxin levels are critical for preventing toxicity (too much) or insufficient effectiveness (too little). High levels can cause dangerous heart rhythm disturbances, while low levels may mean your medication isn’t working as intended. Regular monitoring helps balance safety and treatment goals.
Short name
Free Digoxin Level
Frequently asked questions
How often should I get this test?
What does a 'free' digoxin test differ from a total digoxin test?
Can I eat or drink before 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 17, 2026. · Read our editorial policy