Desvelado

English speakers may be surprised to learn that Spanish has a special-purpose verb meaning stay up late: desvelarse. It covers everything from merely staying up past your bedtime to staying up all night, whether intentionally or due to factors outside of your control: noise, insomnia, etc.

• Ayer se desveló. Yesterday he got to bed rather late.
• Nos desvelamos. We stayed up all night.

Desvelarse often includes the idea that you are sleepy as a result of having stayed up. However, it doesn't work for sleepiness due to other factors.

The verb is usually used pronominally: an accompanying object pronoun (me, te, se, ...) agrees in number and person with the subject: él se desveló.

Desvelado

The corresponding adjective is desvelado.

— ¿Te pasa algo?
— No, no me pasa nada. Simplemente estoy un poco desvelado. (I'm just a bit sleepy from having gone to bed late.)

Desverlarse and desvelado are so commonly heard that you'll wonder how you got along with them. Resist the urge to say, Tengo mucho sueño porque anoche dormí muy tarde. Just say, Es que ando desvelado. Simple.