Digoxin: Ask Us

At a Glance

Why Get Tested?

To determine if the concentration of digoxin in your blood is at a therapeutic level or to detect toxic levels

When to Get Tested?

After the start of digoxin therapy and at regular intervals to ensure that drug levels are within therapeutic range (not low or at toxic concentrations)

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?

No special preparation is needed, but timing of the sample for testing is important. When having your blood drawn, tell the laboratorian when you took your last dose of digoxin.

The Test Sample

What is being tested?

Digoxin is a drug used to treat heart failure and abnormal heart rhythms. This test measures the amount of digoxin in the blood. Heart failure, including congestive heart failure (CHF), causes the heart to become less effective at circulating blood. As a result, blood backs up into the legs, hands, feet, lungs and liver, causing swelling, shortness of breath, and fatigue.

Digoxin is prescribed to alleviate some symptoms of heart failure. It strengthens the contractions of the heart and helps it to pump blood more efficiently. Digoxin also helps control the heart rate and abnormal heart rhythms known as arrhythmias. It will not cure heart failure or arrhythmias, which are chronic conditions, but can help to manage the symptoms along with diet, exercise, and other medications.

Digoxin levels need to be monitored because digoxin is a drug with a narrow safety range. If the level in the blood is too low, symptoms may recur. If the level is too high, toxicity may occur.

Digoxin dosage may be adjusted based on levels measured.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No special preparation is needed, but timing of the sample for testing is important and your doctor may tell you to have your blood drawn a specific number of hours after your last dose of digoxin. When having your blood drawn, tell the laboratorian when you took your last dose. You may want to write down the exact time at which you took your dose and when the blood was drawn. This information will be useful if your doctor has any questions about your levels.

The Test

How is it used?

A digoxin test is used to monitor the concentration of the drug in the blood. The dose of digoxin prescribed may be adjusted depending on the level measured. A doctor may order one or more digoxin tests when a person begins treatment to determine if the initial dosage is within therapeutic range and then order it at regular intervals to ensure that the therapeutic level is maintained. A digoxin test may also be used to determine if symptoms are due to an insufficient amount of the drug or to digoxin toxicity.

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When is it ordered?

The test to measure digoxin is ordered at the beginning of drug therapy to ensure correct dosage. Digoxin takes approximately one to two weeks to reach a steady level in the blood and in the target organ, the heart. A test done at that time will reflect more accurately whether a person is receiving the right amount of digoxin.

Once the dosage level is determined, digoxin levels are monitored routinely, at a frequency determined by the doctor, to verify correct dosage and if any changes occur in drug source, dosage, or other medications taken at the same time.

A digoxin test may be ordered when it is suspected that levels are too low in someone who is taking the medication and who is showing signs of heart failure such as:

Fatigue
Shortness of breath
Swelling in the hands and feet (edema)

The test may be done when toxicity is suspected and the affected person has signs and symptoms such as:

Dizziness
Blurred vision or seeing yellow or green halos
Vomiting
Diarrhea
Irregular heartbeat
Difficulty breathing

Changes in health status can affect levels of digoxin and its ability to control symptoms. Digoxin tests may be done and the dose adjusted if necessary when someone experiences a physiologic change that may affect blood levels and effectiveness of digoxin. This may be when someone develops, for example, kidney or thyroid problems, cancer, or stomach or intestinal illness.

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What does the test result mean?

The therapeutic range for digoxin has been established over time as 0.5-2.0 ng/ml for those being treated for heart failure. Several new studies suggest a more narrow range, 0.5-1.0 ng/ml, may be appropriate for some people. The recommended range for someone with arrhythmia is 1.5-2.0 ng/ml. Most people find that their symptoms improve when their digoxin levels are within these ranges.

It is important to note that each person's response to medications is individual and other factors such as kidney function or concurrent medications may be involved. If someone's symptoms do not improve or if the person is experiencing side effects, then the doctor may need to adjust the digoxin dose up or down according to that person's needs.

If results do not fall within the therapeutic range but the person tested is not experiencing symptoms, then the doctor will evaluate the case and decide if it is necessary to adjust the person's dose. Whether or not the dose needs to be adjusted, the doctor may order additional digoxin tests to determine the resulting blood level.

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Is there anything else I should know?

Several prescribed and over-the-counter drugs can affect the level and effectiveness of digoxin. It is important for those taking digoxin to tell their doctor about all medications and supplements they are taking and to notify the doctor when there are any changes in medication.

Digoxin is primarily cleared from your system by the kidneys. When someone has kidney problems, their doctor may want to monitor kidney function and blood potassium levels since kidney dysfunction and low levels of potassium can result in symptoms of digoxin toxicity.

In cases where toxic levels of digoxin are found, antidigoxin antisera may be administered to reverse the effects of the drug.

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Common Questions

1. How long will I need to be on digoxin?

Digoxin is prescribed to treat heart failure, a long-term, chronic condition. It will not cure heart failure but will help to control it. Digoxin is usually taken and monitored throughout your lifetime. Very rarely is it ever discontinued.

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2. Who orders digoxin tests?

Your primary doctor may order the test, but it also may be monitored by a cardiologist.

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3. Why is it important to have my blood drawn for my digoxin test at a certain time?

Timing of the digoxin blood test is important because if the sample is drawn too soon after dose, the results of the test may be erroneously high and will show a toxic level when that is not the case. The sample should be drawn at least 6-8 hours after the last dose. Many times, the blood sample will be drawn just before the next dose is to be taken.

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Related Pages

On This Site

Conditions: Heart attack, Heart disease, CHF, Hypertension, Kidney disease

Elsewhere On The Web

American Heart Association: Living with heart failure
National Heart, Lung, and Blood Institute: Heart failure
National Heart, Lung, and Blood Institute: Heart arrhythmia
National Health Information Center, Drug Digest: Digoxin
American Academy of Family Physicians, Digoxin: A Medicine for Heart Problems
American Heart Association: Medications Commonly Used to Treat Heart Failure
U.S. Food and Drug Administration: Avoiding Drug Interactions

» See all Article Sources

Article Sources

« Return to Related Pages

NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

(Revised 2010 January). What is Heart Failure? National Heart Lung and Blood Institute [On-line information]. Available online at http://www.nhlbi.nih.gov/health/dci/Diseases/Hf/HF_WhatIs.html through http://www.nhlbi.nih.gov. Accessed February 2010.

A.D.A.M. Editorial Team (Updated 2009 February 3). Cardiac glycoside overdose. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/002581.htm. Accessed February 2010.

Dugdale, D. (Updated 2009 January 23). Digitalis toxicity. MedlinePlus Medical Encyclopedia [On-line information]. Available online at http://www.nlm.nih.gov/medlineplus/ency/article/000165.htm. Accessed February 2010.

Ahmed, A. (2008 May 21). An Update on the Role of Digoxin in Older Adults with Chronic Heart Failure. Medscape Today from Geriatrics & Aging 2008;11(1):37-41 [On-line information]. Available online at http://www.medscape.com/viewarticle/573855 through http://www.medscape.com. Accessed February 2010.

Patel, V. and James, P. (Updated 2010 January 6). Digitalis Toxicity. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/154336-overview through http://emedicine.medscape.com. Accessed February 2010.

Sources Used in Previous Reviews

A Manual of Laboratory & Diagnostic Tests. 6th ed. Fischbach F, ed. Philadelphia: Lippincott Williams & Wilkins; 2000.

Clinical Chemistry: Principles, Procedures, and Correlations. Bishop M, Duben-Engelkirk J, Fody E, eds. 4th ed. Philadelphia: Lippincott Williams & Wilkins; 2000.

Sacher RA, McPherson RA, Campos J. Widmann's Clinical Interpretation of Laboratory Tests. 11th ed. Philadelphia: F.A. Davis Company; 2000.

Goodman & Gilman's The Pharmacological Basis Of Therapeutics. 11th Edition. Lazo J, Goodman L S, Parker K L, eds, McGraw-Hill, September 2005.

National Heart, Lung, and Blood Institute (September 2003). Heart and Vascular Diseases: Heart Failure: Summary page (On line information). Available onlin at http://www.nhlbi.nih.gov/health/dci/Diseases/Hf/HF_All.html through http://www.nhlbi.nih.gov.

Terra, S G, Washam J B, Dunham, G D, and Gattis W A, (Oct 1999). Therapeutic Range of Digoxin's Efficacy in Heart Failure: What Is the Evidence? Pharmacotherapy, 19(10): 1123-1126, (On line journal). Available online at http://www.medscape.com/viewarticle/418044 through http://www.medscape.com.

Gibbs C R, Davies M K Davies, Lip G Y H, (Feb 2000). Management: Digoxin and other inotropes, Beta-blockers, and antiarrhythmic and antithrombotic treatment, BMJ. 320(7233): 495-498. PDF available for download at http://www.pubmedcentral.gov/articlerender.fcgi?tool=pmcentrez&artid=1127534 through http://www.pubmedcentral.gov.

Mihai Gheorghiade, MD; Kirkwood F. Adams, Jr, MD; Wilson S. Colucci, MD (2004). Digoxin in the Management of Cardiovascular Disorders, Circulation; 109:2959-2964 (On line journal). Available online through http://circ.ahajournals.org.

Rich, M. (2003 September). Drug Therapy of Heart Failure in the Elderly. Am J Geriatr Cardiol 12(4):235-242 (On line journal). Available online at http://www.medscape.com/viewarticle/460844 through http://www.medscape.com.

Yusuf, S (November 1997). Digoxin in heart failure: results of the recent digoxin investigation group trial in the context of other treatments for heart failure Eur Heart J, 18: 1685-1688. PDF available for download through http://eurheartj.oxfordjournals.org.

The Digitalis Investigation Group, (February 1997). The Effect Of Digoxin on Mortality and Morbidity in Patients with Heart Failure, NEJM volume 336:525-533 (On line journal). Available online at http://content.nejm.org/cgi/content/full/336/8/525 through http://content.nejm.org.

Catherine A. Hammett-Stabler, PhD, DABCC, FACB. Pathology and Laboratory Medicine, UNC-Chapel Hill.