A testosterone test is a blood test that measures the amount of the hormone, testosterone, in your blood. Testosterone contributes to several important functions in your body including muscle and fat mass, sexual function and desire, bone health, energy, concentration, and other symptoms.
Why it's done
A low testosterone is associated with several symptoms including increased fat mass, difficulty putting on muscle, decreased energy, fatigue, difficulty concentrating, anemia (low blood count), erectile dysfunction, decreased libido, and other similar symptoms. Men who experience one or more of the above symptoms may have the test obtained to determine if a low testosterone may be contributing to the symptom.
There is little risk in getting a testosterone test. You may have some soreness or tenderness around the site where your blood is drawn. Rarely, the site may become infected.
How to prepare
Testosterone levels fluctuate throughout the day, and are highest in the morning. To get an accurate number, this test should be drawn between the hours of 6 to 10 in the morning. You do not need to fast for the test.
What you can expect
A testosterone test is a blood test, usually done in the morning several hours after waking. Blood is drawn from a vein, usually from your arm. Before the needle is inserted, the puncture site is cleaned with antiseptic, and an elastic band is wrapped around your upper arm. This causes the veins in your arm to fill with blood.
After the needle is inserted, a small amount of blood is collected into a vial or syringe. The band is then removed to restore circulation, and blood continues to flow into the vial. Once enough blood is collected, the needle is removed, and the puncture site is covered with a bandage.
The entire procedure will likely last a couple of minutes. It's relatively painless.
There are no special precautions you need to take after your testosterone test. You should be able to drive yourself home and do all your normal activities. The results takes 24-48 hours to come back, so please be sure to have it drawn ahead of time so that we can discuss the results at your appointment.
In the United States, testosterone levels are measured in nanograms (ng) per decileter (dL) of blood. In Canada and many European countries, testosterone levels are measured in nanomoles per liter (nmol/L). To interpret your tests, use these general guidelines.
- Below 300 ng/dl (10.4 nmol/l) = low
- 300-950 ng/dl (32.9 nmol/l) = normal
- Above 950 ng/dl (32.9 nmol/l) = high