Drug monitoring is performed to make sure the drug dosages are correct. The test checks the level of medicine or drug into the blood. Sometimes, medicine amount that is helpful  may be very close to the harmful  amount. It is difficult to determine the correct doses for each person.

The dose necessary to produce the therapeutic level in the blood varies from person to person. Factors affecting blood medication levels are age, weight, activity level the speed at which the body breaks down medication, the way of taking medication and other medications that the person is using

It used for the people whose body is not able to break down the medicines in proper manner, infants, older adults, people with heart failure and heart disease like arrhythmia or if the people are taking two medicines which may interfere with each other.

The blood sample will be taken from the arm vein. An elastic belt will be wrapped over your upper arm, which will result in enlargement of the veins below band. The needle site will be cleaned with antiseptic and needle will be inserted into the vein. More than one needle sticks may require.

A tube will be attached to needle to fill it with the blood. You have to remove the band after collecting adequate blood. After removing the needle, apply the gauze over the needle site and apply pressure and bandage at last.