A testosterone test measures the blood level of the male sex hormone testosterone.
Testosterone, which plays an important role in sexual development, is produced mainly
by the testes in boys and in much smaller amounts by the ovaries in girls. Testosterone
is also produced by the adrenal glands in both girls and boys.
In young boys, testosterone levels are normally low. As puberty approaches —
usually between the ages of 10 and 14 — the pituitary gland (a pea-sized gland
near the base of the brain) secretes two hormones (luteinizing hormone, or LH; and
follicle-stimulating hormone, or FSH) that work together to stimulate the testes to
Increased testosterone production is what causes boys to develop deeper voices,
bigger muscles, and body and facial hair. It also helps the testes produce sperm,
and it plays a role in speeding a boy's growth in height during puberty. Testosterone
is also important for bone health.
Two separate assessments may be performed as part of a testosterone test:
total testosterone, which measures the entire amount of testosterone
in the body, including both the amount bound to proteins that help transport the hormone
through the bloodstream and free testosterone
free testosterone, which measures only the testosterone that's
not attached to proteins
The doctor may order one or both tests. However, because sexual development involves
many other hormones, a more complete picture can often be obtained by performing other
tests at the same time, including an LH or FSH test. For example, low levels of testosterone
can be due to a problem with the testes' production of testosterone or to the pituitary
gland not making enough of the hormones that stimulate the testes to produce testosterone.
Why It's Done
Doctors may order a testosterone blood test if a boy appears to be entering puberty
earlier or later than expected. High levels are associated with precocious (early)
puberty, while low levels may indicate a delay in sexual development. In girls, high
levels can be associated with the appearance of masculine characteristics, such as
The test may also be used in either boys or girls to check for damage or disease
of the testes, ovaries, adrenal glands, or pituitary gland, or to check for steroid
In teens and adults, testosterone levels can help doctors evaluate fertility or
menstrual problems and sexual function.
No special preparations are needed for this test. The doctor may want to perform
the test in the morning, when testosterone levels usually are highest.
On the day of the test, it may help to have your child wear a T-shirt or short-sleeved
shirt to allow easier access for the technician who will be drawing the blood.
A health professional will clean the skin surface with antiseptic, and place an
elastic band (tourniquet) around the upper arm to apply pressure and cause the veins
to swell with blood. Then a needle is inserted into a vein (usually in the arm inside
of the elbow or on the back of the hand) and blood is withdrawn and collected in a
vial or syringe.
After the procedure, the elastic band is removed. Once the blood has been collected,
the needle is removed and the area is covered with cotton or a bandage to stop the
bleeding. Collecting blood for this test will only take a few minutes.
What to Expect
Collecting a sample of blood is only temporarily uncomfortable and can feel like
a quick pinprick. Afterward, there may be some mild bruising, which should go away
in a few days.
Getting the Results
The blood sample will be processed by a machine and the results are commonly available
after a few days.
The testosterone test is considered a safe procedure. However, as with many medical
tests, some problems can occur with having blood drawn. These include:
fainting or feeling lightheaded
hematoma (blood accumulating under the skin causing a lump or bruise)
pain associated with multiple punctures to locate a vein
Helping Your Child
Having a blood test is relatively painless. Still, many children are afraid of
needles. Explaining the test in terms your child can understand might help ease some
of the fear.
Allow your child to ask the technician any questions he or she might have. Tell
your child to try to relax and stay still during the procedure, as tensing muscles
and moving can make it harder and more painful to draw blood. It also may help if
your child looks away when the needle is being inserted into the skin.
If You Have Questions
If you have questions about the testosterone test, speak with your doctor.