Truth serum is traditionally read as the fear, or the wish, that everything hidden would come out. It points to secrets, honesty and how much you are ready to let others see.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.