I also take Citracal - Calcium Citrate Petites (smaller size, easier to swallow) with Vitamin D. The tablets are coated. The label says Vitamin D3 = 400 IU and Calcium 400 mg. Directions = take 1 to 2 tablets two times daily. I never have had an upset stomach. I will probably find just a Calcium supplement for summer as I also am outside all the time mowing grass, planting flowers and tending to my flower gardens, and swimming with my daughter and granddaughters.