If your pre workout stops giving you energy you should first check your sleep quality and daily diet because lack of sleep and insufficient food can make you feel tired even when you take supplements regularly.
Sometimes your body may become less sensitive to the caffeine in your pre workout when you use it frequently so taking a break from caffeine can help restore some of its effects.
If your pre workout is no longer working like before try improving your sleep schedule and getting enough rest because supplements cannot replace proper recovery.
You can try having a balanced meal with carbohydrates and protein before training because your body needs enough fuel to perform well during intense workouts.
Instead of increasing your pre workout dose immediately consider reducing your caffeine intake gradually if you use it heavily because suddenly stopping high caffeine intake can cause headaches and tiredness.
One common reason pre workout stops feeling effective is frequent caffeine consumption from coffee energy drinks tea and other supplements because all these sources can contribute to caffeine tolerance.
You should also check whether your supplement has expired or has been stored improperly because product quality and storage conditions can affect its freshness and reliability.
Try reviewing your workout timing because training after a long workday or several hours without food can make you feel drained even when your supplement contains caffeine.
Sometimes taking pre workout late in the evening can disturb your sleep and create a cycle where you feel tired the next day and need more caffeine to get through your workout.