Your doctor might order a testosterone test for a variety of reasons---whether you are a male or a female. It's important to have your doctor interpret your test results because the normal testosterone range will vary depending on your age and stage of maturity. The "normal" range also is extremely broad. Testosterone levels are always determined with a blood test, according to the National Institutes of Health.
Function
If you are a male, your doctor may order a testosterone test if you have early or delayed puberty, testicular tumors or erectile dysfunction. If you are female your doctor may order the test if you have irregular periods, hirsutism, a condition in which you have excessive body hair in areas where men typically get it, or virilization, a condition in which a woman gains male characteristics like a deepening voice or increased muscularity. It may be ordered for either a male or female for decreased sex drive, infertility or hypothalamus or pituitary disorders.
Procedure
When the test is performed, blood will be drawn from a vein. This usually is done on the back of your hand or inside of your elbow. Your health-care provider will clean the area with an antiseptic and wrap an elastic band around your upper arm. This creates pressure to the area that makes your vein swell with blood. The medical worker inserts a needle into your vein and collects your blood into an airtight tube attached to the needle. The provider collects blood into a small glass tube, onto a slide or onto a test strip, according to the National Institutes of Health.
Features
"Normal" value ranges for testosterone tests can vary slightly among laboratories, notes NIH. Generally a normal level of testosterone for a man is 300 to 1,200 nanograms per deciliter. In general the normal range for a woman is 30 to 95 ng/dL, according to NIH. According to the Mayo Clinic, your testosterone levels will peak during adolescence and young adulthood. As you age, your level will gradually decline. The typical decline is about 1 percent per year after the age of 30.
High Levels
Abnormal results from your testosterone test can mean a variety of things. High levels can be caused by ovarian or testicular cancers. It also can be a sign of an adrenal gland disorder called congenital adrenal hyperplasia, which can affect males and females. In boys it can be a sign of precocious puberty, and in girls or women it can be a sign of polycystic ovary disease. It also can be caused by androgen resistance in males, a condition in which you are resistant to male hormones and take on the physical characteristics of a woman although you have the genetic makeup of a man. Anabolic steroid use can raise levels as well.
Low Levels
Lower than normal levels of testosterone may be the result of delayed puberty, chronic illness, testicular failure, a noncancerous pituitary tumor called a prolactinoma or hypopituitarism, meaning your pituitary gland doesn't produce normal amounts of its hormones. In men, low testosterone levels also can be caused by impaired testosterone production due to damage to the testes from physical injury or alcoholism.
Considerations
Your doctor may advise you to quit taking certain medications prior to your testosterone test. Barbiturates, anticonvulsants and clomiphene can cause your testosterone levels to rise. If you are a woman taking estrogen therapy, this also may increase your testosterone levels.
Time Frame
Your testosterone levels will vary and generally are highest in the morning. That's why blood testing for testosterone usually is done early in the day, notes the Mayo Clinic. If you are a male who has delayed or slow-developing puberty, your testosterone test may be done along with follicle-stimulating hormone (FSH) and luteneizing hormone (LH) tests.
