A single fasting growth hormone (GH) level is of limited value. The secretion of GH is episodic and pulsatile. GH has a half-life of 20 to 25 minutes. Testing for growth hormone deficiency or excess is best done as part of a dynamic test involving specific stimuli (see the online Endocrine Appendices: Growth Hormone Stimulation and Growth Hormone Suppression). Insulin-like growth factor-1 can also be useful in assessing growth hormone status.

Insulin-like Growth Factor 1, also known as IGF-1, is used as a biomarker for blood levels of human growth hormone. It is a hormone produced by the liver and other tissues which affects growth-promoting activities and glucose metabolism. The blood level of IGF-1 appears to fluctuate over 24 hours and is found to be related to growth hormone secretion.

Ferritin is a protein that stores iron. Red blood cells need iron to form normally and carry oxygen around your body. Low levels of ferritin lead to iron deficiency anemia, which means you have too few red blood cells. High levels of ferritin can damage your joints, heart, liver, and pancreas.

The serum iron test measures the amount of iron in your blood. The total iron-binding capacity (TIBC) test looks at how well the iron moves through your body.

B12 and folic acid blood testing help doctors diagnose central nervous system disorders, anemia, and malabsorption syndromes. B12 and folic acid also play an important role in energy level, muscle strength and memory. Because B12 and folate are derived solely from dietary intake, such as egg yolks, beef, poultry and fish, many people are deficient in these important vitamins.