You should take your multivitamin with a meal in order to maximize the digestive effects of stomach acids and to help control the release of the pill contents over a longer period of time. If you are also taking a calcium supplement in a carbonate form (calcium carbonate), you can take it at the same time, which is what we recommend for best results including ease of compliance. Also, take only 500 mg of calcium at a time because that’s about all the body can use effectively from one dose. Therefore, if your health professional tells you that you need to add 1000 mg/day of calcium in the form of a supplement, take calcium carbonate in 2-doses: 1 500 mg tablet with a morning meal and 1 with an evening meal. Only if for some reason you need to take calcium on an empty stomach, should you use calcium citrate because your body can it break down without stomach acid - otherwise both are absorbed equally. However, calcium carbonate gives you more for your money because 500 mg of calcium carbonate contains twice as much elemental calcium as the same amount of calcium citrate (40% by weight versus 21%, respectively).