Sign in →

Test Code DIG Digoxin Level, LAB23


Chemiluminescent Immunoassay

Performing Laboratory

St. Luke's Hospital Cedar Rapids

Specimen Requirements


Preferred: Green-top (lithium heparin) tube

Acceptable: Gold-top serum gel tube or plain red-top tube

Specimen Volume: 0.1 mL of  plasma or serum

Stability: Serum or plasma should be physically separated from cells as soon as possible with a maximum limit of two hours from time of collection.  Separated specimens should be analyzed immediately or kept at 2 – 8°C and analyzed within 7 days. For longer storage, samples may be frozen at -20°C for up to 6 months. 


Collection Instructions: To obtain steady state concentrations, levels should be drawn 6 to 8 hours after the daily dose or just prior to next scheduled dose.



  1. Digoxin time to steady state is 5 to 7 days.
  2. Digoxin metabolites, cardiac glycosides, and some synthetic steroid-like medications can interfere in assay of digoxin due to cross-reactivity with digoxin-specific antibody.  In addition, the presence of endogenous Digoxin-Like Immunoreactive Factor in some specimens may interfere due to cross-reactivity with the digoxin-specific antibody. Apparently toxic digoxin levels can occur in patients receiving both digoxin and diuretics due to electrolyte imbalances, not assay cross-reactivity.
  3. Human anti-mouse antibodies or other heterophile antibodies may be present in patient specimens. This assay has been specially formulated to minimize the effects of these antibodies, however results from patients known to have these antibodies should be carefully evaluated.
  4. Levels may be ordered any time toxicity is suspected.
  5. This assay is affected by biotin interference.


Reference Values

Therapeutic range: 0.8-2.0 ng/mL

Critical value: >2.5 ng/mL

Day(s) Test Set Up

Monday through Sunday

Test Classification and CPT Coding


Useful For

Digoxin levels are measured to help physicians keep dosages in therapeutic ranges. Digoxin is a widely prescribed drug used in the treatment of congestive heart failure, atrial fibrillation, atrial flutter, supraventricular tachycardia, and other cardiac disorders.