A test that measures the concentration of digoxin in blood.

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band or blood pressure cuff is placed around the upper arm to restrict blood flow through the vein. This causes the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

Consult the health care provider about the need to take (or not take) usual medications before the test.

In infants and children, the preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For specific information on how you can prepare your child, see the following topics:

• Infant test or procedure preparation (birth to 1 year)
• Toddler test or procedure preparation (1 - 3 years)
• Preschooler test or procedure preparation (3 - 6 years)
• Schoolage test or procedure preparation (6 - 12 years)
• Adolescent test or procedure preparation (12 - 18 years)

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

The main purpose of this test is to monitor patients taking digoxin in order to determine the effective drug dosage and prevent toxicity. Monitoring of drug levels is important in people taking digitalis medications such as digoxin, because the margin of safety between therapeutic levels and toxic levels is narrow.

Normal values range from 0.8 to 2.0 ng/ml.

Note: ng/ml = nanogram per milliliter

• Inadequate or excessive medication dosage
• Digitalis toxicity is present or is likely to develop (elevated value)

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)
• Multiple punctures to locate veins

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.