Vitamin D in Children
Vitamin D doesn’t get nearly as much attention as it deserves in pediatric care. It’s essential for bone development, immune function, and even mood regulation, yet deficiency is common across all age groups, including children who spend time outdoors and drink milk regularly. At Pediatricz Now, we check vitamin D levels as part of a broader picture of your child’s nutritional health, because low levels often go unnoticed until there’s already an impact.
What Vitamin D Actually Does in a Growing Child’s Body
Most people associate vitamin D with bones, and that connection is real. Vitamin D regulates how the body absorbs calcium and phosphorus, both critical for building and maintaining strong bone structure during childhood and adolescence. Without enough of it, bones don’t mineralize properly. In younger children, severe deficiency can lead to rickets, a condition where bones become soft and prone to deformity. In older children, the more common concern is bones that are weaker than they should be for their age.
But bone health is only part of the story. Vitamin D also plays a role in immune function, helping the body mount appropriate responses to infection. There’s growing research on its connection to mood and mental health as well, with low levels associated with increased risk of depression in children. It’s also involved in wound healing and supports normal brain development.
The body can produce vitamin D through direct sun exposure, but the amount varies significantly depending on skin tone, time of year, cloud cover, sunscreen use, and how much time a child actually spends outside with skin exposed. Diet fills some of the gap, but very few foods contain meaningful amounts of vitamin D naturally. Fortified milk, fatty fish, egg yolks, and cod liver oil are among the better sources, and most children don’t eat enough of these consistently to meet their needs through food alone.
Which Children Are Most at Risk for Deficiency
Vitamin D deficiency is more widespread than many parents expect. Estimates suggest around 15% of children between ages 1 and 11 are deficient, and that number climbs significantly among certain groups.
Children with darker skin tones are at higher risk because melanin, the pigment that gives skin its color, naturally reduces the skin’s ability to produce vitamin D from sunlight. Darker-skinned children may need five to ten times more sun exposure to produce the same amount of vitamin D as lighter-skinned children, making dietary sources and supplementation especially important.
Obesity is another significant risk factor. Vitamin D is fat-soluble, meaning it gets stored in fat tissue. In children with higher body fat, more vitamin D gets sequestered and becomes less available for the body to use, even when intake appears adequate.
Other children at elevated risk include those who are breastfed without vitamin D supplementation (breast milk does not contain sufficient vitamin D on its own), those following vegan or heavily restricted diets, children with conditions affecting nutrient absorption such as celiac disease or cystic fibrosis, and those on certain medications including anti-epileptics or long-term corticosteroids. Children who spend very little time outdoors, whether due to lifestyle, cultural dress practices, or geographic location, are also more vulnerable.
How We Assess and Address Low Vitamin D Levels
Vitamin D deficiency is diagnosed with a simple blood test measuring 25-hydroxyvitamin D, the form of vitamin D the body stores and uses. Your child does not need to fast before this test. Routine screening is not recommended for every child, but we do recommend testing when risk factors are present or when symptoms suggest deficiency may be a factor.
Symptoms of low vitamin D in children can be easy to miss or attribute to other causes. Bone pain, especially in the legs or lower back, muscle weakness, fatigue, and increased susceptibility to illness are the most common presentations. In infants, delayed development can be a sign. Because these symptoms overlap with many other conditions, testing is the only reliable way to confirm deficiency.
When levels come back low, treatment depends on how deficient a child is and what’s driving it. Mild insufficiency is often addressed with dietary changes and a daily vitamin D supplement. Children with confirmed deficiency may need higher doses under medical supervision. More significant deficiency, especially in children with absorption issues or underlying conditions, may require higher-dose supplementation with follow-up testing to confirm levels are coming up appropriately.
One thing worth knowing: it is possible to over-supplement vitamin D, and excessive amounts can cause problems including kidney stones. Supplementation without testing first and without appropriate dose guidance is not something we recommend.
When Professional Guidance May Be Helpful
If your child falls into any of the higher-risk groups, has symptoms that could point to deficiency, or hasn’t had their vitamin D levels checked and you’ve been wondering about it, a visit is a reasonable next step. We can run the bloodwork, review your child’s diet and lifestyle, and put together a supplementation plan that’s appropriate for their age and specific situation.
Frequently Asked Questions
Can my child get too much vitamin D from sunscreen-free outdoor play?
Does vitamin D affect my child's teeth, not just their bones?
Yes. Vitamin D plays a direct role in tooth development and mineralization. Children with chronic vitamin D deficiency are at higher risk for enamel defects and early tooth decay. This is one of the less commonly discussed effects but a clinically relevant one, particularly in younger children whose teeth are still developing.
If my child takes a daily multivitamin, is that enough?
It depends on the multivitamin and your child’s individual risk profile. Many standard children’s multivitamins meet general daily recommendations for healthy kids with no deficiency. But a multivitamin alone is rarely sufficient for children who are already deficient or who have conditions that affect absorption. Testing is the only reliable way to know whether what your child is taking is actually moving the needle.
Can vitamin D deficiency affect my child's athletic performance or muscle recovery?
It can. Vitamin D plays a role in muscle function, and low levels have been linked to reduced muscle strength and slower recovery after physical activity. For active children and teen athletes, this is worth factoring in, especially if your child is experiencing unexplained fatigue, frequent muscle soreness, or performance that doesn’t match their training effort.
How long does it take to correct a vitamin D deficiency once we start supplementing?
It varies based on how low levels are and how the child responds to supplementation. In many cases, follow-up testing after 8 to 12 weeks of consistent supplementation gives a clearer picture of whether levels are improving. Children with absorption issues may take longer and may need ongoing monitoring rather than a one-time correction.