How do you say i am sick today in spanish?

If you are a boy, you say "estoy enfermo" (I am sick)

If you are a girl, you say "estoy enferma" (I am sick)

Tú estas enfermo/a - You are sick (informal)

Usted esta enfermo/a - You are sick (formal)

Tú eres enfermo/a - (you are sick[in the head])