Q. When a man wakes up in the morning, should he always have an erection? If he does not, should he see a doctor?
A. Nocturnal erections are part of the normal physiologic rhythm for men. There is nothing sexual about nocturnal erections. The erections are the body’s way of refreshing the blood in the penis. Unlike other parts of the body that have a high blood flow all the time, the blood flow to the penis is low during the flaccid (soft) state. When the penis is erect, the blood flow goes up. That means that most of the time, the penis is low on blood flow — which translates into low oxygen and low nutrients. Therefore, at night the body cycles the blood in the penis to bring in oxygen and remove toxic waste. This usually occurs during deep sleep.
The man you are asking about is almost certainly still going through these cycles while he is sleeping. Unless he has difficulty with his erection during sex, there is probably no need to see a doctor. If you are really concerned, you could perform the stamp test. This is done by attaching a postage stamp to the shaft of the penis before he goes to bed. If there is an erection while he is sleeping, than the stamp will be split when he wakes up.