to add to sth that you have just done by doing sth else
follow sth up
to add to sth that you have just done by doing sth else
You should follow up your phone call with an email or a letter.
follow sth up
to find out more about sth that sb has told you or suggested to you
The police are following up several leads after their TV appeal for information.
Definiciones del Oxford Advanced Learner's Dictionary, 9.ª edición