The growth hormone (GH) blood test determines the levels of growth hormone in the blood. If they are low the treatment is prescribed.

The growth hormone (GH) stimulation test measures the ability of the body to produce GH.

How the test is performed?

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:

  1. 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).
  2. The first sample is drawn early in the morning.
  3. Medication 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 medication is best.
  4. Additional blood samples are drawn over the next few hours.
  5. After the last sample is taken, the IV line is removed. The pressure is applied to stop any bleeding.

How to prepare for the test?

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 a doctor if you should stop taking any of your drugs before the test.

How the test 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.

Why the test is performed?

This test is most often done to find out whether a growth hormone deficiency (GH deficiency) is causing current health disorders in adults of middle age.

Normal Results

Normal results include:

  • For adult males — 0.4 to 10 nanograms per milliliter (ng/mL), or 18 to 44 picomoles per liter (pmol/L)
  • For adult females — 1 to 14 ng/mL, or 44 to 616 pmol/L
  • For children — 10 to 50 ng/mL, or 440 to 2200 pmol/L

A normal value rules out HGH deficiency.

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

What abnormal results mean?

If this test does not raise GH levels, there is a reduced amount of HGH stored in the anterior pituitary. 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. A doctor can tell you more about this and help you select the most suitable and safest medication just for you.

To get a free consultation and ask any questions about the test or HGH therapy, just get in touch.

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