It depends on whether you breast-feed your baby or how much vitamin D-fortified formula or cow's milk your baby is drinking.

Consider these guidelines from the American Academy of Pediatrics for vitamin D for babies:

• If you're breast-feeding or partially breast-feeding your baby, give your baby 400 international units (IU) of liquid vitamin D a day — starting soon after birth. Continue giving your baby vitamin D until you wean your baby and he or she drinks 32 ounces (about 1 liter) a day of vitamin D-fortified formula or, after age 12 months, whole cow's milk.
• If you're feeding your baby less than 32 ounces (about 1 liter) a day of vitamin D-fortified formula, give your baby 400 IU of liquid vitamin D a day — starting in the first few days after birth. Continue giving your baby vitamin D until he or she drinks at least 32 ounces (about 1 liter) a day.

When giving your baby liquid vitamin D, make sure you don't exceed the recommended amount. Carefully read the instructions that come with the supplement and use only the dropper that's provided.

While breast milk is the best source of nutrients for babies, it likely won't provide enough vitamin D. Your baby needs vitamin D to absorb calcium and phosphorus. Too little vitamin D can cause rickets, a softening and weakening of bones. Since sun exposure — an important source of vitamin D — isn't recommended for babies, supplements are the best way to prevent vitamin D deficiency.

As your baby gets older and you add solid foods to his or her diet, you can help your baby meet the daily vitamin D requirement by providing foods that contain vitamin D — such as salmon, egg yolks and fortified foods.

If you have questions about your baby's need for vitamin D supplements, consult your baby's doctor.