Nature's Bounty Vitamin D3 125 mcg, 400 SoftgelsED. 04 2028 Natures Bounty Vitamin D3 provides 125 mcg (5000 IU) of the potent and active form of vitamin D in a once daily softgel. Vitamin D can act as a hormone in the body as it is involved in the regulation of several very important functions. Often referred to as the sunshine vitamin because it is synthesized in the skin upon exposure to sunlight. Features A Potent and Active Form of Vitamin D Supports Strong Bones and Healthy Immune Function