Vitamin D3 (as opposed to D2) is recommended most often because it is the naturally occurring version of vitamin D in your body. D2 is poorly absorbed. Other possible names for vitamin D supplements include: Alfacalcidol, Calcifediol, Calcipotriene, Calcipotriol, Calcitriol, Colecalciferol, Dihydrotachysterol, and Paricalcitol. Vitamin D is a fat-soluble nutrient, which means that you need to have eaten a little bit of fat in order for the nutrient to be absorbed efficiently by your body. Fat-soluble nutrients (the other ones are A, E and K) take a long time to be absorbed and eliminated by your body because they are stored in your fatty tissues and liver.  Always take your vitamin D supplements with or right after you have eaten a meal. The food in your system will help your body to process this nutrient. It doesn’t seem to matter what meal you take your supplement with. The time of day does not appear to affect your body’s ability to absorb vitamin D. Certain medications interact with the absorption of vitamin D supplements and prevent healthy absorption. These medications include: Antacids, Lipitor, Dovonex, Lanoxin, Cardizem, Dilacor, Tiazac, Cytochrome P450 3A4 (CYP 3A4) substrates, Verapamil and water pills. Cofactors are nutrients that work together to help the body absorb as much of the nutrients as possible. For example, magnesium is known to be a co-factor of vitamin D. This means that eating foods that are rich in magnesium, or taking magnesium supplements, may help your body to absorb vitamin D more efficiently. Other nutrients that are thought to help your body absorb vitamin D include:  Boron. Foods that are rich in boron include almonds, apples, hazelnuts, dates, and avocados. Vitamin K. Foods that are rich in vitamin K include basil, kale, spinach, scallions, Brussels sprouts, and asparagus. Zinc. Foods that are rich in zinc include oysters, crab, beef chuck, fortified breakfast cereal, lobsters and baked beans. Vitamin A. Foods that are rich in vitamin A include sweet potatoes, carrots, kale,...

TL;DR in Chinese:
选择适当的维生素D补充剂。 在一天中最丰盛的一餐服用维生素D补充剂。 服用维生素D补充剂之前，先仔细检查你目前服用的药物。 考虑增加摄入维生素D的辅助因子。 减肥。 和医生一起治疗可能影响身体吸收维生素D的潜在疾病。