Vitamin D is an essential nutrient, and it has many roles in the body. For instance, it helps regulate the amount of calcium in the body.

You need vitamin D to make your bones and teeth strong. Without enough of it, your bones can become thin, weak, or misshapen.

Vitamin D is also crucial for growing infants and children. Their bones need a lot of vitamins and minerals to support their rapid growth. In addition to keeping their bones healthy and strong, vitamin D also helps with their immune system, heart, brain, and other organs.

Your baby should be getting 400 international units (IU) a day of vitamin D, beginning in the first few days of life.

Breast milk only contains about 5–80 IU per liter (L), so a supplement of 400 IU per day of oral vitamin D drops is recommended for all breastfed infants. This includes babies who are sometimes breastfed and sometimes given infant formula.

Vitamin D drops are available over the counter. You can ask your pediatrician for a recommended brand. Be sure to read the label to find out how many drops of the product to give your infant.

You may decide to later wean your baby off of breast milk and only use vitamin D-fortified infant formula. If you do, additional supplements won’t be necessary as long as they drink at least 1 liter per day. All formulas sold in the United States have at least 400 IU of vitamin D per liter.

Once you wean your child off of formula, offer them vitamin D-fortified milk.

The best source of vitamin D is sunlight. The exact amount of sunlight people need to make enough vitamin D depends on their skin color, the time of day they’re outside, and the time of the year.

When ultraviolet (UV) rays from the sun hit the skin, it triggers your body to synthesize vitamin D. Once in your body, vitamin D needs to be activated through a process known as hydroxylation.

A vitamin D deficiency is usually caused by not getting enough sunlight.

Pregnant or nursing mothers don’t usually get enough vitamin D to provide for both themselves and their babies. This is why babies who are exclusively breastfed are at a higher risk of vitamin D deficiency. Breast milk contains very little vitamin D.

Risk factors for a vitamin D deficiency include:

Avoiding the sun or using sunscreen

While getting more sunlight can be beneficial for vitamin D, many people today are avoiding too much sunlight exposure or using sunscreen. This is because of the increased risk of skin cancer.

Skin cancer is the most common cancer in the United States. One type, known as melanoma, can be fatal.

Most cases of skin cancer are caused by exposure to UV light from the sun. High exposure to sunlight also leads to skin aging.

Wearing protective clothing when out in the sun

While the sun is the best source of vitamin D, you should keep your baby out of direct sunlight and have them wear protective clothing to avoid sunburns. For this reason, your baby will need another source of vitamin D in order to keep them healthy.

Living in certain environments

People who live in northern latitudes don’t get a lot of sun, especially during the winter months. For that reason, it can be hard to make enough vitamin D.

Living in an area with high levels of air pollution or dense cloud cover can also affect your vitamin D levels.

Having certain medical conditions

Certain conditions, such as celiac disease, cystic fibrosis, and inflammatory bowel disease (IBD), can affect the way that your body absorbs vitamin D.

Not getting enough vitamin D in your diet

Good sources of vitamin D include fatty fish and egg yolks. However, it’s found naturally in very few foods.

For this reason, vitamin D is often added to certain foods and beverages, such as milk. This process is called fortification.

Even with fortified foods, many people still don’t get enough vitamin D. Vegans or vegetarians are at a particularly high risk for a deficiency, as their diets may not include any fish, eggs, or milk.

Having dark skin

Dark skin doesn’t react as strongly to sunlight. As a result, people with dark skin often need more sunlight exposure to generate similar amounts of vitamin D as people with lighter skin.

Dark-skinned babies are at a higher risk of developing vitamin D deficiency or the bone disease known as rickets. That’s because dark-skinned mothers are also more commonly deficient in vitamin D.

According to a 2014 study, breastfeeding among African-Americans is associated with higher incidence of nutritional rickets.

Breastfed babies who don’t receive vitamin D supplements are at an increased risk of developing a condition known as rickets.

In rickets, the bones fail to mineralize. This leads to soft bones and skeletal deformities such as bowed legs, thick wrists and ankles, and a projected breastbone.

If not treated, rickets can also lead to many complications, including:

The bone deformities of rickets can usually be fixed if the child is given vitamin D as soon as possible. Some infants may need to have surgery to correct the bone deformities.

Beginning in the 1930s, people in the United States began fortifying their dairy milk with vitamin D. This change has made rickets a rare disease, but there are still a few cases a year. Rickets is still a major public health concern in many developing countries.

Since the diagnosis of vitamin D deficiency has been increasing, its role in health and disease has been a focus of much research. Vitamin D deficiency has been proven to cause osteoporosis.

A variety of other conditions are suspected of being linked to vitamin D deficiency, but research is ongoing. These conditions include:

Human milk is still considered the best source of nutrients for your baby in their first year of life. If possible, infants should only drink breast milk for the first 6 months of life. Breastfed babies will need vitamin D drops in order to meet their daily requirements.

If you have any concerns regarding the safety of vitamin D supplements for your baby, be sure to contact your doctor. If your baby develops bone pain, muscle weakness, or obvious skeletal deformities, seek medical help.


Jacquelyn has been in a writer and research analyst in the health and pharmaceutical space since she graduated with a degree in biology from Cornell University. A native of Long Island, NY, she moved to San Francisco after college, and then took a brief hiatus to travel the world. In 2015, Jacquelyn relocated from sunny California to sunnier Gainesville, Florida, where she owns 7 acres and 58 fruit trees. She loves chocolate, pizza, hiking, yoga, soccer, and Brazilian capoeira.