Taking vitamin pills will not give you energy when you are tired. Vitamins do not supply calories, which are the true sources of energy for your body. Calories come from food in the form of carbohydrates, fats and proteins. Some vitamins act like helpers that work to transform calories from food into energy your body can use. The best source of vitamins is a well-balanced diet. To keep energy levels high, maintain an adequate intake of both calories and vitamins by eating a variety of nutrient-dense foods such as vegetables, fruits, whole grains, beans, lean meats, low-fat dairy foods and healthy fats every day.
Source: American Dietetic Association