A Answers (2)
Mehmet Oz, MD, Cardiology, answeredEven if you consider yourself a sexual Olympian, some nights you may simply be too tired for sex. Fatigue is a widely recognized cause of erectile dysfunction. It's not really clear why tiredness has this mood-dampening effect. However, if part of your brain is thinking "I need sleep," then it's probably not sending powerful signals instructing your penis to engorge with blood and become erect. No worries--fatigue-related erectile dysfunction is usually temporary. Chances are you'll be good as new in the morning.
Honor Society of Nursing (STTI) answered
Being tired can lead to erectile dysfunction. Sex takes energy, both physical and mental. When your body needs to rest, it avoids the activities that are the least crucial. That includes sex. Also some other medical problems such as low-testosterone production can cause both tiredness and erectile dysfunction.
Always talk to your doctor if you are unable to get or maintain an erection more than 25 percent of the time.