Most people need about 400 to 800 international units (IUs) of vitamin D each day, though different people have different requirements. For instance, as you age, your need for vitamin D may increase. People over 70 need at least 600 IUs per day. Be careful not to overdose on vitamin D. Try to keep your intake from supplements below 2,000 IUs per day. Taking too much vitamin D can cause your body to absorb too much calcium, which can lead to nausea, headaches, and muscle and bone weakness. Talk to your doctor to find out how much vitamin D you need.

You can find some vitamin D in egg yolks, cod liver oil, and fatty fishes like salmon. Fortified foods, including milk and some cereals, also have some vitamin D, though you would have to eat a lot to meet your daily needs. Your skin also naturally makes vitamin D from sunlight. About 15 minutes of sunlight two to three times each week—without sunscreen and with hands, face, and arms exposed—can provide enough vitamin D. Most multivitamin supplements provide 100 percent of the daily value (about 400 IUs). But keep in mind, your vitamin D requirement may be higher than this daily value.

You don’t have to get vitamin D at the same time you get your calcium. Once vitamin D goes into your body, it stays in your bloodstream, which means it’s ready to help absorb calcium whenever you eat foods high in calcium or take a supplement. Most people can achieve their daily vitamin D needs by taking a basic multivitamin supplement and a calcium supplement that includes vitamin D.