Is it Kirkman Calcium Powder with Vitamin D (Hypoallergenic) safe to feed gliders?, and in that case how much?

It looks like a really good product and I would say it's safe for gliders. But it also depends on what diet you're feeding and if they're getting enough calcium/vitamin d already. For instance, when I brought my first glider home, I would sprinkle a pinch of calcium powder on a slice of apple and was feeding her the pocket pets diet. After I had her for about 10 days, she became very lethargic. I took her to the vet and found out she had a calcium deficiency. After changing her diet, her numbers improved and I no longer have to supplement. Many glider diets like BML and HPW are formulated to give them balanced nutrition.