Testosterone gel 1% is a clear, colorless gel medicine used because your body does not produce enough testosterone, a condition called hypogonadism. While it is used only externally (applied directly on the skin), it can cause a series of internal side effects, some of which may be quite serious. However, not everyone who takes the medication will have problems. In fact, most people tolerate it quite well. If side effects do occur, in most cases, they are minor and either require no treatment or are easily treated by you or your healthcare provider.

Testosterone gel has been studied thoroughly in clinical trials. During these studies, all potential side effects were carefully documented. In these studies, the most common side effects of Testosterone gel included:

* An enlarged prostate (also known as benign prostatic hyperplasia, or BPH) - in up to 11.7 percent of men
* Abnormal lab tests (various tests, such as cholesterol or blood sugar tests) - up to 9.3 percent
* Acne - up to 8 percent
* Skin reactions at the application site - up to 5.6 percent
* Headaches - up to 4 percent
* Urinary symptoms (such as difficulty urinating or frequent urination) - up to 3.7 percent.