Patient Preparation:  There's not much special preparation required for a digoxin test, but the timing of the sample collection is important: 

 Sample collection: The blood sample should be collected 6-8 hours after your last dose of digoxin. The sample is usually collected just before the next dose is due. 

 Blood draw:

A needle is inserted into a vein in your arm, usually in the back of the hand or inside the elbow. The blood is collected in a syringe or air-tight vial.