An intake of Vitamin D 400 IU is sufficient for your age. You should not go over that amount in supplementation. 2000 IU is the tolerable upper intake level for adults; however, you can be at risk for toxicity (weak muscles, weak bones, excessive bleeding, and kidney stones) if you also consume large amounts of fortified milk / dairy products and fish. Vitamin D is available through our foods - Fortified milk, breakfast cereals, egg yolks, fatty fish, fish oils, and the sun. Sit at a window with the sun shining in for about 1/2 hour (few times a week) and that will help you get enough Vitamin D.