A digoxin test is ordered by your doctor to monitor 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 monitor the level of digoxin at regular intervals to ensure that a therapeutic level is maintained and that toxic levels have not been reached and will not produce symptoms of toxicity.

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 you are receiving the right amount of digoxin. Digoxin levels are monitored routinely at a frequency determined by your doctor after that to verify correct dosage or if any changes occur in drug source, dosage, or other medications taken at the same time. Changes in your health status can also affect levels of digoxin and its ability to control your symptoms. Some physiologic 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 patient’s lifetime.

Timing of the digoxin blood test is important. 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. Timing of the sample collection 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 therapeutic range for digoxin has been established over time as 0.5-2.0 ng/ml for patients being treated for heart failure. Several new studies suggest a more narrow range, 0.5-1.0 ng/ml, may be appropriate for some some patients. The recommended range for patients with arrhythmias is 1.5-2.0 ng/ml. 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 medications is individual and other factors such as kidney function or concurrent medications may be involved. If your symptoms have not improved or if you are experiencing side effects, tell your doctor immediately. He may need to adjust your dose according to your individual needs.

If your result does not fall within therapeutic range but you are not experiencing symptoms, continue to take your medication as prescribed until you consult with the doctor who ordered the test. He will evaluate your case and decide if it is necessary to adjust your dose. If your dose needs to be adjusted, your doctor may order additional digoxin tests to determine the resulting blood level.

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 other medications you may be taking.

Digoxin is primarily cleared from your system by the kidneys. Tell your doctor if you have or have had known kidney problems. Your doctor may want to monitor blood potassium levels since low levels of potassium can result in symptoms of toxicity.

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