She suggested that I take the one with double action. Is it supposed to work on the first try?

Melatonin is typically more effective for aiding in falling asleep rather than maintaining sleep throughout the night. Some individuals may experience residual effects in the morning, especially with higher doses. It is recommended to use a dose of around 3mg if you have difficulty falling asleep. For more information, you can refer to the provided brochure on sleep. Although it was designed for older individuals, the information is relevant for everyone. Hope this helps. Have a great day!