Digoxin Test

A digoxin test is done to adjust the dosage of this drug according to the age, severity of the disease and health condition of an individual so as to obtain the desired effects of the drug. The process is called therapeutic drug monitoring (TDM). TDM of digoxin also helps in determining whether it is suitable to use when you are suffering from other disease conditions or taking medicines that increase the levels of digoxin. Increased age, being underweight, increased calcium and low levels of potassium and magnesium in the blood and kidney diseases are some of the high-risk factors for digoxin toxicity. Doctors order digoxin test when the following symptoms that indicate digoxin toxicity are seen:

• Nausea
• Loss of appetite
• Diarrhoea
• Vomiting
• Drowsiness with confusion of mind
• Disturbances in vision: hazy or unclear vision; appearence of a yellow or green colour halo around objects 

No special preparation is needed for this test. Inform your doctor if you are taking medicines for high cholesterol, high blood pressure (calcium channel blockers) or heart problems, or antibiotics for certain infections. Medicines that contain amiodarone, verapamil, diltiazem, ciclosporin, quinine and atorvastatin increase the level of digoxin in the blood.

A laboratory technician or the nurse will collect your blood sample in a red-top tube and will send it immediately for analysis. 

The first sample is usually collected from six to 12 hours after the drug (digoxin) is taken by mouth and four to six hours after intravenous injection of the drug. Subsequent blood samples are collected after 24 hours and one week to analyse the desired level (therapeutic level) of the drug in the blood, which would not lead to any harmful effect.

Blood tests to measure the levels of potassium, creatinine, magnesium and calcium are done before the digoxin test. Mild side effects such as infection, bleeding and accumulation of blood under the skin at the site of needle prick are seen after the digoxin test.

Normal results:

The ideal levels or normal therapeutic range of digoxin in blood, which are beneficial in the treatment of heart failure and arrhythmia are 0.5-2 ng/mL (nanograms per millilitre) and 1.5-2.5 ng/mL, respectively.

Abnormal results: 

Values higher than the normal results indicate the following:

• Digoxin toxicity
• Kidney diseases
• Use of drugs such as amiodarone, calcium channel blocker medicines, antibiotics (ciclosporin, quinine, etc.) and so on along with digoxin

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.