It depends on few things....the age + size of the dragon and whether the supplement has D3. Babies + young juveniles should have 1 meal a day dusted lightly, but not the second feeding. It's good to have 2 kinds of calcium powder....one WITH D3 , the other without. Too much D3 can cause kidney problems down the road and be deadly in a few days or weeks from the time a dragon begins to act ill. So if you use a MVB [ mercury vapor bulb ] or if your dragon spends time out in the sun he/she will be getting natural D3 and you don't need to use much, so you can use the powder that contains D3 about 2 feedings per week, the other days you can use the calcium without D3. Adults need calcium only about 3X a week, and only 1-2X with D3 if they get exposed to natural sun and or have a strong MVB that produces a good amount of uvb.