I have yet to find an emergency calcium supplement that works as fast and as consistently as Calsorb and I have tried ALL the others. If it's an emergency (ie: post partum eclampsia ) there is NO comparison to the effectiveness of this product. Calsorb has given me positive results in as little as 30 minutes post dosing, while it can take up to two hours in nearly all the other calcium products offered. Two warnings to keep in mind: 1.) Most bitches HATE the taste and often vomit after a dose, but they always retain enough to do the job. 2. Follow dosing directions for your breed and weight to the letter....it CAN be overdosed and an overdose is dangerous...ie: life threatening dangerous. Give smaller tiny doses if you're not sure of the dose and go to a vet ASAP.