Protocols may have to change. The chemistry of your body, and or how it reacts may change. If you gain a ton of weight, or lose a ton of weight it can cause change. Typically it's a good idea to check all your levels every 6 months to a year. The doc I go to requires once a year. Which is awesome, because you can cycle in between there if you want, and have time to have your levels come back to normal.