Even with all the attention ED (erectile dysfunction) and low T (low testosterone) get, it can be hard to know where one starts and the other ends. ED means you have trouble getting an erection firm enough or maintaining it long enough for a satisfying sexual experience. Low T means your testicles are not producing enough of the male hormone testosterone. There are lots of links between ED and low T, but they are not the same condition: Low T can cause ED, but you can have low T and not have ED. You can have ED with normal testosterone levels. Testosterone treatment might help your ED, but it's not the best way to treat it. ED Basics You're a lot more likely to have ED than low T. You have about a 50% chance of having ED to some degree between ages 40 and 70. After age 70, your odds are higher. Although low T is one cause of ED, it's only one of many. The most common cause is poor circulation of blood to your penis. In fact, ED is an early red flag for heart and blood vessel disease. ED affects: 44% of men with heart disease 25% of men with high blood pressure 17% of men with diabetes Low T Basics If you're older than 40, your testosterone level may start falling naturally. About 10% of men ages 40 to 60 have low T. About 20% have it after age 60. But not all men experience low T with age or have symptoms from it. If they do have symptoms, one of them may be ED. Other symptoms of low T include: Fatigue Depression Low interest in sex Common Conditions Found With Low T and ED Though the causes of ED and low T may be different, several health conditions are common in men with low T or ED. Besides older age as a common thread, a correlation exists between men with low T and ED and the following conditions: Diabetes Depression Obesity Treating ED and Low T If you have ED but normal testosterone levels, your health care provider may start treatment with lifestyle changes. These include losing weight, exercising, not smoking, and avoiding alcohol and drug abuse. The next choice for treatment is usually a drug called a phosphodiesterase-type 5 inhibitor (PDE-5 inhibitors). The first of these was a pill called Viagra. If you had ED before 1998, when Viagra first became available, your health care provider might have given you a prescription for testosterone. Today, the PDE-5 inhibitors work much faster and more reliably than testosterone to treat ED. If you have low T with symptoms that include ED, you may get testosterone therapy to increase your sex drive, improve your mood, and increase your muscle and bone strength. Testosterone may also improve ED, but testosterone is not the drug of choice for ED. One option would be to take both testosterone and a PDE-5 inhibitor for low T with ED. Testosterone may increase your desire for sex, while a PDE-5 inhibitor improves your erection. However, a study done at Boston University Medical Center found that adding testosterone to Viagra for men with low T and ED did not make much difference. Finally, know that both ED and low T could be signs of a more serious medical condition, such as heart disease. If you have symptoms of low T or ED, talk with your health care provider about all the possible causes. Key Takeaways Both ED and low T can affect your sexual health. Causes and symptoms of the two conditions are linked, but they are not the same thing. Both conditions may be warnings of a more serious medical problem. Both conditions can usually be treated once you have been checked out by your health care provider.