Question

What would a doctor tell his patient to do (tú commands) or not to do to stay in good health? (If they have the flu)

Answer 1

He could say:

"No comes mala comida"
" Don't eat bad food "

or 

"Tomas tus pastillas"
"Take your pills"

Answer 2

Doctor: tu tienes que tomar ciertos medicamentos y regresar al doctor cada cinco dias 
 
i hope i answered you question