Will it work the first time I use it? Ann September 25, 2019 20:18 Updated Follow Yes. While individual results may vary, sleep should work from the first time you take it. Related articles When should I take it? Will taking Sleep make me groggy? Can I take it every night? How is Rae’s Multivitamin different? Are there any side effects? Comments 0 comments Please sign in to leave a comment.