For bearded dragon owners: I supplement my 5 month old dragon with Reptivite w/ D3 powder by ZooMed. How much should I be using?

Vitamin D helps the body absorb calcium from food for strong bones and teeth. However, too much vitamin D will do the opposite because calcium will leach from bones, and that creates skeletal problems. Therefore only a tiny amount of vitamin D should be given. In fact, most reptile owners use multivitamins to avoid giving pure vitamin D. In fact, I never bothered adding vitamin D to the diet of my amphibians and reptiles. I use calcium powder instead and sprinkle it on their food. For my snakes, I do not even add calcium because I feed them mice, and the snakes get the calcium when they digest the bones. Make sure the supplement you give them have more calcium than vitamin D and you should be okay. 

One way to weigh a lizard is to use a postal scale or kitchen scale. Weigh a box or paper bag and then weigh the lizard with the box or bag and lizard. Subtract the total weight from the box or bag and you have the lizard's weight