It's generally recommended to use red light therapy in the morning, when your body is most receptive to its effects. This is because natural light can help reset your body's biological clock and ensure that you get a good night's sleep. Additionally, exposure to natural sunlight during the day helps boost energy levels and mood, giving you an extra burst of productivity for the day ahead. However, if you are unable to do red light therapy in the morning, it's still beneficial to use it at night as long as you keep your exposure time limited and consistent. Doing so will help ensure that your body has enough time to rest and recover overnight.