As a new parent, it's normal to be concerned about your baby getting everything she needs nutritionally. After all, babies grow at an astounding rate, doubling their birth weights within the first four to six months of life, and proper nutrition is key to proper growth. 

Vitamin D is vital to every aspect of that growth because it helps the body absorb the calcium it needs to build strong bones.

The challenge is that vitamin D isn't found naturally in very many foods, and while it may seem counterintuitive, breast milk doesn't contain enough to meet your baby's needs. 

Why do babies need vitamin D?

Babies need vitamin D because it's necessary for bone development, helping a baby's body absorb calcium and build strong bones.

Babies with extremely low levels of vitamin D are at risk of having weak bones, which can lead to issues like rickets (a childhood disorder in which the bones soften, making them vulnerable to fractures). Plus, building strong bones early on helps protect them later in life. 

Breastfed babies are at higher risk of deficiency than formula-fed infants because while breast milk is the ideal food for a baby, it doesn't contain enough vitamin D to meet your little one's daily needs. That's why your pediatrician will normally prescribe a supplement in droplet form.

Breastfed babies need vitamin D drops the entire time they're breastfeeding, even if they're supplementing with formula, until they start getting enough vitamin D from solids. Talk to your pediatrician about when exactly to transition off the vitamin D supplements.

How much vitamin D do babies need?

Both newborns and older babies need 400 IUs of vitamin D a day until they're 1, after which they'll need 600 IU daily, according to the American Academy of Pediatrics (AAP).[1]

It's important to make sure that your little one gets enough vitamin D because (and it bears repeating), it's needed to help the body absorb calcium. Vitamin D also boosts cell growth, neuromuscular function and immune function.

But you can overdo it. The Food and Drug Administration (FDA) previously released a warning regarding the risk of infants overdosing from liquid vitamin D supplements, especially when the dropper contained more than the daily allowance.[2]

Too much vitamin D can cause a number of side effects including nausea, vomiting, confusion, loss of appetite, excessive thirst, muscle and joint aches, constipation and frequent urination.

Where can babies get vitamin D?

Breastfed newborns and babies should take a vitamin D supplement prescribed by the pediatrician. Babies who are formula-fed may or may not need a supplement. Formula is fortified with vitamin D, and it may be enough to meet your baby's daily needs. Check with your pediatrician about whether your formula-fed baby needs vitamin D drops.

Breastfed babies need to continue taking the vitamin D drops until they've transitioned to solids and are getting enough vitamin D that way. (Again, ask your doctor when you can stop giving your little one a vitamin D supplement.)

Generally, once babies start solid foods, they can get vitamin D from other sources like milk, orange juice, fortified yogurt and cheese, salmon, canned tuna, cod liver oil, eggs, fortified cereals, tofu and fortified non-dairy milks like soy, rice, almond, oat and coconut milk.

If you're concerned that your baby isn't getting enough vitamin D or any other nutrient, you can also add in a daily multivitamin once your infant becomes a toddler.

While the AAP says most healthy children on a well-balanced diet will not need a vitamin supplement, if you'd like your little one to start taking a multivitamin, talk to your doctor about whether it's right for your child and the best brands.[3]

Can babies get vitamin D from sunlight?

Not surprisingly, doctors are wary of too much sun exposure, especially because your little one's skin is oh-so tender. The AAP says that babies under 6 months old should be kept out of direct sunlight completely, and older babies who do go out in the sun should wear sunscreen, hats and other protective clothing.[4]

All that is to say that it's difficult for babies to get any significant amount of vitamin D from the sun alone. Meaning it's all the more important for breastfed babies to take a supplement. 

If you're headed outside, make sure you lather up babies 6 months and older with baby-safe sunscreen with an SPF of 15 (and preferably 30 to 50) at least 30 minutes beforehand and reapply every few hours.

Babies under 6 months should not be covered head-to-toe in sunscreen, but instead can have it applied to small areas of the body, like the backs of the hands, tops of the feet and face.

Do a mother's prenatal vitamins have enough vitamin D for babies?

Nursing moms should keep taking their prenatal vitamins while breastfeeding, but the supplements don't contain enough vitamin D to meet babies' needs. That's why breastfed babies need vitamin D drops until they're able to get enough through their own diets. The typical prenatal vitamin only contains 600 IUs, which isn't nearly enough to cover both Mom and baby.

That said, moms who supplement with 4,000 IUs of vitamin D daily have breast milk that will typically contain 400 IUs per liter or 32 ounces. But since newborn babies are unlikely to take a full feeding of breast milk, you'll need to give them a vitamin D supplement at least at first to ensure that your baby is getting enough until she takes a full feeding. 

Though that's not a practice new moms generally follow, most experts say it's safe. But always check with your pediatrician and OB/GYN to make sure what you're doing is enough for your child.

Pregnant moms should also make sure they're taking in enough vitamin D for their babies-to-be by getting at least 10 to 15 minutes of direct (sunscreen-free) sunshine each day and eating foods high in vitamin D like those listed above.