Blood is drawn several times. Blood samples are taken through an intravenous (IV) line instead of reinserting the needle each time. The test takes between 2 and 5 hours.

The procedure is done the following way:

• An IV is usually placed in a vein, most often the inside of the elbow or the back of the hand. The site is first cleaned with germ-killing medicine (antiseptic).
• The first sample is drawn early in the morning.
• Medicine is given through the vein. This medicine stimulates the pituitary gland to release GH. Several medicines are available. The health care provider will decide which medicine is best.
• Additional blood samples are drawn over the next few hours.
• After the last sample is taken, the IV line is removed. Pressure is applied to stop any bleeding.

DO NOT eat for 10 to 12 hours before the test. Eating food can change the test results.

Some medicines can affect the test results. Ask your provider if you should stop taking any of your medicines before the test.

If your child will have this test, explain how the test will feel. You may want to demonstrate on a doll. The more familiar your child is with what will happen and the purpose of the procedure, the less anxiety they will feel.

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging sensation. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

This test is most often done to find out whether a growth hormone deficiency (GH deficiency) is causing slowed growth.

Normal results include:

• Normal peak value, at least 10 ng/mL (10 µg/L)
• Indeterminate, 5 to 10 ng/mL (5 to 10 µg/L)
• Subnormal, 5 ng/mL (5 µg/L)

A normal value rules out hGH deficiency. In some laboratories, the normal level is 7 ng/mL (7 µg/L).

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

If this test does not raise GH levels, there is a reduced amount of hGH stored in the anterior pituitary.

In children, this results in GH deficiency. In adults, it may be linked to adult GH deficiency.

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight, but may include:

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

Medicines that stimulate the pituitary during the test may cause side effects.