In order to diagnose a growth hormone deficiency in adults, a blood test that best measures growth hormone is needed, sometimes referred to as an “IGF-1 test,” or “HGH test”. The IGF-1 blood test measures the amount of Insulin Like Growth Factor 1 in your blood. A blood test for growth hormone is a little more complicated than other standard blood tests that simply draw blood, because your levels of growth hormone change throughout the day, so it is hard to get an accurate picture, unless you have the test done as early in the morning as possible when your IGF-1 levels are their highest.