Digoxin
At a Glance
Why Get Tested?
To determine if the amount of digoxin in your blood is at an appropriate level or to detect potentially toxic levels
When to Get Tested?
Soon after the start of digoxin therapy and at regular intervals to ensure that drug levels are within the desired range and are not low or at toxic concentrations
Sample Required?
A blood sample collected from a vein in your arm
Test Preparation Needed?
No special preparation is needed, but timing of the sample for testing is important. When you have your blood taken, tell the blood collector when you took your last dose of digoxin. You may want to write down the exact time at which you took your dose and when the blood was taken. This information will be useful if your doctor has any questions about your levels.
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 accumulates in the legs, hands, feet, lungs and liver, causing swelling, shortness of breath, and fatigue.
Digoxin is used to reduce 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 long term conditions, but can, along with diet, exercise, and other medicines, help to manage the symptoms.
Digoxin levels need to be monitored because digoxin is a drug that has a narrow safety range. If the level in the blood is too low, symptoms may recur. If the level is too high, side effects may occur, such as:
- dizziness
- blurred vision or seeing yellow or green halos
- vomiting
- diarrhoea
- irregular heartbeat
- difficulty breathing
Digoxin dosage may be adjusted based on the measured levels.
How is the sample collected for testing?
A blood sample is collected 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. When you have your blood taken, tell the blood collector when you took your last dose of digoxin. You may want to write down the exact time at which you took your dose and when the blood was taken. This information will be useful if your doctor has any questions about your levels.
The Test
How is it used?
A digoxin test is requested by your doctor to measure the level of drug in your blood. The dose of digoxin prescribed by your doctor may be adjusted depending on the level measured. Your doctor will want to measure the level of digoxin at regular intervals to ensure that an appropriate level is maintained.
When is it requested?
The test to measure digoxin is requested at the beginning of drug treatment to ensure correct dosage. Digoxin takes approximately one to two weeks settle down and reach a steady level in the blood and in the the heart. A test done at the right time will be a better indication of whether you are receiving the right amount of digoxin. Digoxin levels will then measured at a frequency decided by your doctor to maintain the right dose, or if any changes occur in the type of tablet, the dose or other medicines taken at the same time. Changes in your health can also affect levels of digoxin and its ability to control your symptoms. Some physiological changes that may affect levels of digoxin in the blood are:
- kidney function
- thyroid problems
- cancer
- stomach or intestinal illness
Digoxin will not cure heart failure but will help to control it. Since digoxin is prescribed to treat patients with a long-term, chronic condition, it is usually monitored throughout the treatment.
Timing of the digoxin blood test is important. The sample should be collected at least 6-8 hours after you last took your digoxin. Very often, the blood sample will be collected just before the next dose is to be taken. Timing of the sample collection is important because if the sample is collected too soon after the drug is taken, the results of the test may be erroneously high and may appear to be toxic when this is not the case.
What does the test result mean?
The appropriate (“target”) range for digoxin has been established over time as 0.5-2.0 micrograms/litre for patients being treated for heart failure. Several new studies suggest a more narrow range, 0.5-1.0 micrograms/litre, may be appropriate for some patients. The recommended range for patients with arrhythmias is 1.5-2.0 micrograms/litre. Most patients find that their symptoms improve when their digoxin levels are within these ranges.
It is important to note that each patient’s response to medicines is individual and other factors such as kidney function or other drugs taken at the same time may be involved. If your symptoms have not improved or if you have side effects, tell your doctor immediately. He/she may need to change your dose to meet your individual needs.
If your result does not fall within the “target” range but you are not experiencing symptoms, continue to take your medication as prescribed until you consult with the doctor who requested the test. He/she will evaluate your case and decide if it is necessary to adjust your dose. If your dose needs to be adjusted, your doctor may request additional digoxin tests to determine the resulting blood level.
Is there anything else I should know?
Several prescribed and over-the-counter drugs can affect the level and effectiveness of digoxin in your system. Be sure to tell your doctor about all other medicines you may be taking.
Digoxin is mainly removed from your blood by the kidneys. Tell your doctor if you have, or have had, kidney problems. Your doctor may want to measure blood potassium levels since low levels of potassium can result in symptoms of toxicity.
In severe cases where highly toxic levels of digoxin are measured, antidigoxin antisera may be given to reverse the effects of the drug. Usually, reducing the dose or stopping the drug for a short time is sufficient to bring levels back to normal quickly.
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