Hi there. Our need for thyroid hormone can vary depending on our age, our weight, our medications, our activity level, other hormone levels, even our diet to some extent. Because of this it is important to check one's levels of the thyroid hormones and adjust one's dose of thyroxine accordingly to keep the levels within the normal range. If you have not had your levels checked within the past 3-6 months, you should call your doctors office and have them ordered for you.
If you feel there have been recent changes in your energy level or your mood or your weight, you should ask you doctor to check your levels to see if they too have changed. This makes sense. Waiting many months to do an "annual check" does not. If your levels have dropped and you are getting more tired, or emotional, or gaining weight, for example, you need to increase your supplements. It is very difficult to function properly and feel well when one's thyroid levels are too low (or too high).