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Test Code FRDIG Digoxin, Free, Serum

Reporting Name

Digoxin, Free, S

Useful For

Evaluating recrudescent (breakthrough) digoxin toxicity in renal-failure patients


Assessing the need for more antidigoxin Fab to be administered


Deciding when to reintroduce digoxin therapy


Monitoring patients with possible digoxin-like immunoreactive factors (DLIFs)

Performing Laboratory

Mayo Medical Laboratories in Rochester

Specimen Type


Specimen Required

Patient Preparation: For 12 hours before this test do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.


Preferred: Serum gel

Acceptable: Red top

Specimen Volume: 1 mL

Collection Instructions:

1. Draw blood 6 to 8 hours after last dose of digoxin.

2. Serum gel tubes should be centrifuged within 2 hours of collection.

3. Red-top tubes should be centrifuged and aliquoted within 2 hours of collection.

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 7 days
  Frozen  180 days

Reference Values

<16 years:

Therapeutic ranges have not been established for patients who are under 16 years of age. In adults, the suggested serum free digoxin therapeutic range is 0.4-0.9 ng/mL.

Toxic concentration: ≥3.0


≥16 years:

0.4-0.9 ng/mL   

Toxic concentration: ≥3.0 ng/ mL

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
FRDIG Digoxin, Free, S 3562-6


Result ID Test Result Name Result LOINC Value
FRDIG Digoxin, Free, S 3562-6

Method Name

Ultrafiltration Followed by Electrochemiluminescent Immunoassay


If not ordering electronically, complete, print, and send a Cardiovascular Test Request Form (T724) with the specimen (