The best time of day to take vitamin D and calcium are different. Vitamin D is fat-soluble and can be taken with milk at breakfast. The best time to take calcium is determined by the type of calcium supplement and is generally recommended to be taken with meals. Vitamin D is fat-soluble, you can choose to take after breakfast, the fat in the food is conducive to vitamin D absorption. Calcium carbonate needs stomach acid to dissociate, so calcium carbonate needs to be taken with meals or after meals, because the body secretes a lot of stomach acid to digest food during meals, and taking it at this time is conducive to the dissociation and absorption of calcium carbonate. Calcium citrate does not need to be dissociated by stomach acid and can be taken before or after meals. Because the body’s ability to absorb calcium is limited, it is recommended that calcium be taken several times a day to improve its absorption. Vitamin D and Calcium need to be used under the guidance of a doctor and should not be used without authorization.