Vitamin D is essential for the functioning of many important systems in the body, and recent research has suggested that we may need much more vitamin D than previously thought for optimum immune function and long-term health. Optimal Vitamin D3 Liquid is a pure and potent Vitamin D3 supplement in an olive oil base, providing 2000 IU of cholecalciferol per drop. Most people do not get sufficient vitamin D3 in their diet, and the synthetic vitamin D2 that is added to dairy products is an inferior form of this vital nutrient, usually added in too small of an amount. Vitamin D3 occurs naturally in fatty fish, cod liver oil, egg yolks, and liver. Optimal Vitamin D3 contains only cholecalciferol derived from cholesterol in sheep"s wool, making it suitable for vegetarians. Some factors that contribute to vitamin D deficiency include: Spending most of the day indoors Using sunscreen Wintertime & less sunny climates Darker skin tone (melanin blocks UVB rays, which produce vitamin D in the skin) Vitamin D deficiency symptoms vary depending on the individual, so consulting with a physician and testing vitamin D levels, as supplementing with too much vitamin D can cause elevated blood calcium levels which can have serious health effects. Measuring 25 hydroxy vitamin D levels is the preferred test for determining vitamin D deficiency. The liquid format of Optimal Vitamin D3 makes it simple to tailor the dose to fit your specific needs, and is easier to take than capsules, especially for small children. Optimal Vitamin D3 Liquid is free of major allergens, preservatives, and flavors. It contains no wheat, gluten, dairy, corn, soy, fish, shellfish, or nuts.