Vitamin D3 Tablets 5000iu are a specific, highly bio-available form of Vitamin D, providing 5000iu per tablet. Vitamin D is a fat soluble vitamin that contributes to muscle function, normal bones, immune function as well as playing a role in cell division. Vitamin D3, also referred to as Cholecalciferol, can be consumed in the diet, although it’s present in relatively few foods. Oily fish alongside fortified dairy and cereal products are the most common sources of Vitamin D. Exposure to sunlight is responsible for Vitamin D synthesis, and is responsible for the majority of Vitamin D ‘intake’ in the body. Vitamine D is best used from october till april.