18 Month old not talking yet, should we be worried or no?

Hi,Our 18 month old has one word that he uses correctly (Up) and mostly babbles. He understands other words/phrases (dog, door, park, outside, come here, brush your teeth, careful etc...) Our pediatrician has said if he doesn't have more words by August we should look into hearing tests and therapy. Anyone experience anything similar? How did it turn out?Note: He does not have any siblings and does not go to daycare. via /r/Parenting http://bit.ly/2QkdHtD