The purpose of testosterone testing is to evaluate the amount of testosterone in the blood. Testosterone levels that are outside of a normal range can cause changes to health and physical appearance. Measuring testosterone can be helpful in diagnosing medical conditions or monitoring a patient’s response to therapy:
- Diagnosis: Doctors may check testosterone levels to determine the cause of a persons’ symptoms. Testing can help identify testosterone deficiency or an elevated level of testosterone. Testosterone tests may be part of assessing patients with health conditions that can affect hormone levels.
- Monitoring: Monitoring is how doctors follow a patient’s health over time. In people who have had abnormal testosterone tests in the past, follow-up testing may be used to track their testosterone levels.
Testosterone tests can also be used to monitor the health of transgender men. Transgender men are people who were assigned female at birth but identify as male. Some transgender men may choose to take hormone therapy to change their physical appearance to match their gender identity. Doctors may monitor testosterone levels in this group of men to ensure testosterone levels are maintained at a certain level.
What does the test measure?
A testosterone test measures the level of the hormone testosterone in the blood.
In men or anyone with a penis, testosterone is produced by the testicles and the adrenal gland, and it controls the development of sperm and male sex characteristics. In women or anyone with ovaries, testosterone is produced by the ovaries, the adrenal gland, and other tissues, and it aids in overall growth and development.
Testosterone in the blood can be either bound or free:
- Bound testosterone is attached to proteins such as albumin or sex hormone binding globulin (SHBG). Most testosterone is bound to SHBG.
- Free testosterone, the active form, is all the remaining testosterone that is not bound to other substances.
A total testosterone test measures both bound and free testosterone in a sample of blood. This is the most common type of testosterone test, and levels are commonly reported in nanograms per deciliter of blood (ng/dL). Less often, a test may be performed for free testosterone, which is reported in picograms per deciliter of blood (pg/dL).
Another less common test is for bioavailable testosterone, which is testosterone that can be used more readily by the body. Bioavailable testosterone includes all testosterone that is not bound to SHBG, including free testosterone and albumin-bound testosterone. Bioavailable testosterone is also commonly reported in nanograms per deciliter of blood (ng/dL).
When should I get a testosterone test
Your doctor may order a testosterone test if you are experiencing symptoms that suggest hormone levels outside of a normal range.
In men or anyone with a penis, a testosterone test may be performed if you have symptoms that suggest a low testosterone level, such as:
- Early or late onset of puberty
- Erectile dysfunction
- Fertility problems
- Osteoporosis or thinning of the bones
- Decrease in sex drive
Doctors may also evaluate your testosterone levels even if you don’t have symptoms if you have a health condition that can affect hormone levels. For example, testosterone testing may be performed if you have HIV/AIDS, unexplained bone density loss, infertility, or anemia. If you have undergone certain types of cancer treatment such as chemotherapy or radiation to the testicles, you may also have your testosterone levels checked.
Doctors may check testosterone levels as part of a diagnostic work-up in women or anyone with ovaries if physical changes suggest a higher than normal level of testosterone. Changes may include the following:
- Irregular periods
- Loss of periods
- Changes in hair growth patterns
- Voice changes
- Skin changes such as oily skin or acne
- Enlarged clitoris
You may also have testosterone testing if you are a transgender man on masculinizing hormone therapy that is intended to induce and maintain male sex characteristics. Testing is recommended every three months during the first year of therapy as your dose is adjusted. After that, your doctor may suggest monitoring your testosterone levels one to two times per year.
If you have questions about testosterone testing, talk with your health care provider who can discuss whether this testing is appropriate in your situation.