Adult or child:

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 a tourniquet is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to fill with blood. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. The tourniquet is then removed to restore circulation. After blood has been collected the needle is removed, and the puncture site is covered to stop any bleeding.

Infant or young child:

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. A bandage may be applied to the puncture site if there is any bleeding.

In the laboratory, a radioimmunoassay (a test that tags proteins making them visible for study) is performed on the sample.

No special preparation is necessary.

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.

This test is performed if you have diabetes, and insulin no longer seems to control it, or if you appear to have an allergic response to insulin.

This test measures your immune system's response to insulin. Your health care provider may use the test to confirm insulin resistance, or to investigate the cause of your insulin allergy.

Normally, antibodies against insulin are not present in your blood. Normal value ranges may vary slightly among different laboratories.

If IgG and IgM types of antibodies against insulin are present, your body reacts as if the insulin is foreign.�This may make insulin less effective, or neutralize it. The antibodies can also change the amount of time the insulin takes to act, putting you at risk for low blood sugar. This means that the insulin cannot serve its intended function of moving glucose from the blood stream into the cells. As a result, increased levels of insulin are required for the same therapeutic effect. This phenomenon is called insulin resistance.

If the test shows elevated values of IgE antibody against insulin, then your body has developed an allergic response to the medication. This could put you at risk for skin reactions, or more severe widespread reactions. Other medications such as antihistamines or low dose injectable steroids may help to lessen the reaction. If reactions have been severe, an in-hospital procedure called desensitization may be necessary.

Risks associated with venipuncture are slight:

• Excessive bleeding
• Fainting or feeling lightheaded
• 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.