A testosterone test measures the amount of testosterone in the blood. It is also called a serum testosterone test. Testosterone (sometimes referred to simply as “T”) is a hormone produced by both males and females. It plays a role in puberty and fertility. It also affects sexual desire.
In males, most T is produced in the testes. In females, most is produced in the ovaries. Males have higher levels than females, and it is thought to have a significant influence in the development of many particular “male” traits: increased muscle bulk, higher bone mass, physical strength, and body hair, amongst others. However, the hormone plays an important role in women as well.
Why Is the Test Ordered?
This test is ordered for different reasons in males and females.
Testosterone in Males
One common reason to order this test is either early or delayed puberty. The test may also be ordered if low hormone levels are suspected. Low levels are also known as hypogonadism.
Symptoms of hypogonadism include:
- decreased body hair
- decreased muscle mass
- low sex drive
- erectile dysfunction
- growth of breast tissue
Causes of low T include:
- delayed puberty
- testicular damage (caused by trauma, alcoholism, or mumps)
- hypothalamic disease
- pituitary disease
- noncancerous pituitary tumor
A number of genetic diseases can also affect T levels, including:
- Klinefelter syndrome
- Kallmann syndrome
- myotonic dystrophy
High T levels may also be problematic. They may be caused by:
- early (precocious) puberty
- hyperthyroidism (overactive thyroid)
- anabolic steroids
- congenital adrenal hyperplasia
- androgen insensitivity syndrome
- testicular tumor
- adrenal tumor
Testosterone in Females
In females, testing is usually for high T levels. This may cause:
- irregular or absent menstrual periods
- development of facial and body hair
- deepened voice
High T may be caused by:
- polycystic ovarian syndrome (PCOS)
- congenital adrenocortical hyperplasia
- ovarian cancer or tumor
- adrenal tumor
How to Prepare for the Test
Certain drugs can affect your testosterone levels. These could change the results of this test. Therefore, it is important to tell your doctor about all medications you are taking. Include both over-the-counter and prescription drugs. Your doctor may ask you to stop certain drugs before your test.
Medications that may affect this test include:
- estrogen therapy
Your doctor may specify a time of day for your test. Hormone levels are highest in the morning. Therefore, this test is often performed between 7 a.m. and 10 a.m.
You may be also sent for repeat testing. This can track hormone changes throughout the day.
What Happens During the Test
A testosterone test requires a blood sample.
The technician will clean the area where the blood will be drawn. Blood is usually taken from a vein on the inside of the elbow or the back of the hand.
An elastic band will be tied around your upper arm. This makes blood pool in the vein. A sterile needle will be inserted into your vein. Blood will be drawn into a tube. The elastic band will be removed from your arm. Then the needle will be removed. Pressure will be applied to stop bleeding and prevent bruising. A bandage may be applied as well.
Having your blood taken may cause some pain or discomfort. It may feel like a pricking or burning sensation. Relaxing your arm can help ease the pain. You may continue to feel some throbbing after the needle is removed. This should quickly go away.
What Are the Risks?
A blood test has few risks. Rare complications include:
- multiple puncture wounds from trouble finding a vein
- excessive bleeding
- feeling lightheaded or fainting
- hematoma (a collection of blood under the skin)