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Digoxin Testing

What is digoxin testing?

A digoxin test is a blood test that your doctor can use to determine the level of the medication digoxin in your blood. Digoxin is a drug that contains cardiac glycosides. People take it to treat heart failure and irregular heartbeats. Digoxin is available in oral form. Your body absorbs it, and it then travels to your body’s tissues, especially your heart, kidney, and liver.

Your doctor performs digoxin testing to make sure that you aren’t receiving too much or too little of the drug. Your doctor should monitor the level of digoxin in your blood because the drug has a narrow safe range.

Why is a digoxin test performed?

Cardiac glycoside, the active ingredient in digoxin, is a potentially poisonous chemical if you take it in large amounts or over a long period in incorrect doses. It’s important for your doctor to check the amount of digoxin in your blood regularly while you’re taking the drug. Young children and older adults are at an especially high risk for toxicity, or digoxin overdose.

It’s also important for your doctor to monitor the levels of digoxin in your system because the symptoms of digoxin overdose can be similar to the symptoms of the heart condition that caused you to need the drug in the first place.

Your doctor will likely order several digoxin tests when you first start using the drug to establish the appropriate dose. You doctor should continue to order the tests at regular intervals for as long as you’re taking the drug. They should also order the tests if they suspect you’re receiving too much or too little of the medication.

If the level of digoxin in your system is too low, you may experience the symptoms of heart failure. These symptoms include:

  • fatigue
  • shortness of breath
  • edema, or swelling in your hands and feet

If the level of the drug in your system is too high, you may have symptoms of an overdose. These typically include:

  • dizziness
  • seeing yellow or green halos around objects
  • nausea
  • diarrhea
  • vomiting
  • difficulty breathing
  • irregular heartbeats
  • confusion
  • abdominal pain

How is a digoxin test performed?

Your doctor will check your levels of digoxin by testing a sample of your blood. They’ll probably ask you to go to an outpatient clinical laboratory to give a blood sample. The healthcare provider at the lab will draw blood from your arm or hand with a needle.

Tell your doctor about all medications and supplements you’re taking in addition to digoxin. This includes medications that don’t need a prescription. Taking digoxin within six to 12 hours before your test can also affect your result. Some prescription, over-the-counter, and supplemental drugs can affect the level of digoxin in your body, making it either too high or too low. These include:

  • antibiotics
  • antifungal medications
  • St. John’s wort
  • certain blood pressure medications
  • anti-inflammatory medications, such as nonsteroidal anti-inflammatory drugs

Ask your doctor if you should stop taking any medications before your test. It may be helpful to write down the time you took your digoxin and the dose so you can share that information with your doctor. Your doctor will often check your blood chemistry in addition to your digoxin level.

What risks are associated with digoxin tests?

The risks of a blood draw are low. Some people experience mild pain or dizziness while having their blood sample taken.

After the test, the puncture site may have:

  • a bruise
  • slight bleeding
  • an infection
  • a hematoma, or a blood-filled bump under your skin

What do the test results mean?

If you’re receiving treatment for heart failure, the normal level of digoxin is between 0.5 and 2.0 nanograms of medication per milliliter of blood (ng/ml). If you’re being treated for a heart arrhythmia, the normal level of the drug is between 1.5 and 2.5 ng/ml. If your tests results fall outside of the normal range, your doctor will adjust your digoxin dose accordingly.

Most people find that their symptoms improve when their digoxin levels stay within these ranges. Your doctor will adjust the dose if your symptoms don’t improve, they’re getting worse, or you’re experiencing adverse side effects.

Though results can vary, the levels of toxic concentration are generally anything greater than 4.0 ng/mL. This level of digoxin in the blood can be life-threatening. However, results can vary depending on your sex, health history, the test method, and other factors.

If your test results don’t fall within the therapeutic range but you aren’t experiencing symptoms, your doctor will determine if they need to adjust your dose. Your doctor may ask you to take additional digoxin tests to determine the exact level of digoxin in your blood and the next treatment step.

Content licensed from:

Written by: Heather Ross and Brian Wu
Medically reviewed on: Jun 27, 2016: Judi Marcin, MD

This feature is for informational purposes only and should not be used to replace the care and information received from your health care provider. Please consult a health care professional with any health concerns you may have.
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