If you have gallstones and osteoporosis, you need to pay attention to a few things when supplementing calcium. First, choose easily absorbable calcium sources, such as calcium tablets or calcium-rich foods like milk, yogurt, and green vegetables. Secondly, don't forget to take vitamin D along with calcium, as it helps with calcium absorption. Avoid high-fat and high-cholesterol foods, as these can worsen gallstones. Finally, it's best to do this under a doctor's guidance to ensure safety and effectiveness.