Although in common parlance “sleepy” and “tired” are used interchangeably, there is actually an important difference between the two. Sleepy refers to a tendency to fall asleep, while tired simply implies physical and/or mental fatigue. So it’s quite possible to be tired without being sleepy: just remember those times you were physically exhausted, but couldn’t fall asleep because your mind was racing.
From a sleep point of view, this is an important distinction. If you have a problem with your sleep, it will have direct daytime consequences: you will feel sleepy. But if you are tired during the day, it could be the result of any number of reasons: a long drive, a boring job or a stressful event, for instance. Of course you may naturally feel a bit sleepy when you wake up in the morning, or in the early afternoon when you undergo a natural reduction in alertness (the so called ‘post-lunch dip’).
But if you really feel that you could easily fall asleep at 11am, then there may well be a problem with your sleep. That’s why it’s so important to distinguish between feeling tired and feeling sleepy. If you do have a sleep problem, you need to find a way to solve it. Don’t let anything stand between you and a good night’s sleep!