Signs of Vitamin D Deficiency in Babies

Published on April 30th, 2021

Your prenatal vitamins seemed to contain a whole alphabet of nutrients to ensure your baby develops well in your womb. But what happens after you meet your little bundle of joy in person? What nutrients does she need when she’s a growing baby out in the world?

Vitamin D is one of the most important nutrients your baby should be ingesting, but it’s also one of the trickiest ones for babies to get during the first six months after birth. Without it, babies may have a hard time developing strong bones and teeth and sustaining the health of other parts of their physiology, which we’ll go into more below. 

What is vitamin D? 

Vitamin D is a fat-soluble vitamin that is present in the foods we eat. Fat-soluble means that this vitamin is stored in the body’s fat for long-term use. While vitamin D can be absorbed in the foods that we eat, our body can also naturally produce vitamin D with the help of two important ingredients: 

  • 7-dehydrocholesterol, a kind of cholesterol the body stores in the skin
  • Sunlight exposure

When ultraviolet light from the sun meets the skin, the energy from that light converts 7-dyhydrocholesterol into vitamin D. To maintain healthy vitamin D levels using just sunlight, adults only need 10-30 minutes in direct sun a few times a week (a lunchtime walk will do it!). Because of this, adults who spend enough time in the sun typically don’t have to worry about getting enough vitamin D in their diets—their bodies do the vitamin D work for them! 

For babies, things get a little more complicated. 

Why is your baby at risk for vitamin D deficiency? 

Does everything you eat go to your baby? In short, yes! During pregnancy, a baby gets all the vitamins he needs from Mom, which is a good thing because scientists haven’t figured out a way to put a skylight in a pregnant mom’s belly (…yet.). So babies spend those nine months enjoying the warm, comforting dark of the womb while still getting enough vitamin D…until they’re born, or as it’s said in many romance languages, brought to the light (how beautiful is that?).

After they’re born, babies face a risk for vitamin D level deficiencies for a few reasons:

  • Babies aren’t ready to be out in the sunlight (yet). It might be tempting to plop your newborn on a lawn chair and let him soak up those vitamin-D-producing rays (plus, how cute would that be?). But your child still has a lot of growing to do before he’s ready for direct sunlight. His baby skin is incredibly sensitive to sun damage for the first six months of life because melanin, a cell that protects your baby’s skin from excessive harm from the sun, hasn’t been developed yet. Melanin production is only triggered by sunlight, so it only begins after your baby’s birth. In the first six months, indirect light exposure will gradually increase your baby’s melanin so that after six months of age, he can be outside in the sunshine with the protection he needs
  • There isn’t enough vitamin D in breast milk. In fact, the US National Institutes of Health reported that 81% of women of childbearing age have insufficient levels of vitamin D. If breastfeeding mothers doesn’t have enough vitamin D for her health, they may not have enough to ensure her baby is getting enough Vitamin D intake for his health.
  • Infant formula has higher amounts of vitamin D than breast milk, but it isn’t always a sure bet. According to the CDC, 32 ounces of infant formula can provide the right amount of formula your baby needs. But how much of that formula is your baby actually getting? Between spit-ups, messy slurps, spills, and fussy spells (your baby’s not yours!), it can be difficult to ensure your baby is ingesting enough formula to ensure proper vitamin D levels. 

Why is vitamin D so important for babies? 

Why does your baby need vitamin D in the first place? Vitamin D supports several of the most important parts of your baby’s growth. 

  • Bone development – Vitamin D helps your child build healthy bones by ensuring proper calcium absorption in the body. Calcium is one of the most important elements in bone development, and it is vital to your child at this stage because babies grow a lot. Babies have an extraordinary growth rate, gaining about an inch of length every month, so it’s important to have enough calcium to power this growth. Normal vitamin D levels enable your baby to absorb up to 40% of the calcium he ingests. When you have low vitamin D levels, that absorption rate goes down to 10-15%
  • Making little teeth – It will be a while before your baby is taking his first bite of solid food, but his body will work on developing teeth long before it’s nibbling time. Much like bones, calcium is a key ingredient to healthy teeth. And, as we mentioned, the more normal those vitamin D levels are, the more calcium your child’s body can use to make his first chompers.  
  • Heart health – Scientists are still finding connections between healthy vitamin D levels and the health of other parts of a child’s body like the vascular system, heart, brain, stomach, muscle systems, and endocrine glands. 

Does your baby need plenty of vitamin D? D stands for definitely. What can happen if he doesn’t get this important nutrient?

Side Effects of Vitamin D Deficiency 

When it comes to a lack of vitamin D for babies, side effects in the long term include: 

  • Rickets: A disease that causes softness and weakness in bones. It can occur after prolonged vitamin D deficiency.
  • Seizures: Due to low calcium levels for proper brain function.
  • Heart issues: Since vitamin D has been linked to muscle strength. Because the heart is a muscle, a baby’s heart can weaken if there isn’t enough vitamin D to support the vascular system.  

Thankfully, there are plenty of ways to spot low vitamin D levels before your child comes anywhere near these side effects. 

Signs of Vitamin D Deficiency in Babies 

Vitamin D deficiency is extremely treatable, and it can be helpful to know the signs and ensure your baby is on track for all of her vitamin needs.

Vitamin D deficiency in babies symptoms include:

#1 Slow Growth Rate

Vitamin D is required for proper bone and muscle growth. Since babies are little growing machines, lack of growth is a definite sign to give your child’s healthcare provider a call. 

#2 Crankiness or Lethargy

Lack of vitamin D can cause muscle cramping and bone pain in a little one. If a child loses her playful attitudes and alertness and seems especially irritable without any known cause, it might mean something more is going on with her body. 

#3 Tetany 

Tetany is a condition in which there isn’t enough calcium in a baby’s bloodstream. Remember, vitamin D helps ensure that your baby is absorbing plenty of calcium. When your child runs low on vitamin D, that also means she’s running low on calcium. Tetany can cause apneic spells—or episodes where it seems like your child is having a hard time breathing—wheezing, muscular weakness, and, in the worst cases, seizures. 

How To Ensure Your Child Gets Enough Vitamin D 

A vitamin D deficiency can seem daunting, but the good news is there are several simple ways you can ensure your baby is getting everything he needs to grow up healthy and happy with all the vitamin D his body requires. 

Supplement Both Formula and Breast Milk with Vitamin D Supplements 

When it comes to child multivitamins, the first thing that might come to mind are those Flintstones vitamins you may have eaten as a kid. But babies have a ways to go before they start enjoying chewable, fruity, or cartoony vitamins. Instead, pediatricians recommend vitamin D supplementation by adding 400 international units (UI) of vitamin D in the form of vitamin drops to your baby’s diet once a day soon after birth. 

  • If you’re breastfeeding, continue with this dosage until your breastfed infant is weaned or until he can drink 32 ounces a day of vitamin D-fortified formula or, after he reaches 12 months, whole cow’s milk.
  • If you’re using formula, keep giving your baby vitamin D supplements until he can drink a minimum 32 ounces of formula every day.

As your baby gets older and graduates from breastmilk or formula, you can also make sure that you are introducing the best first baby foods to help your little one maintain proper vitamin levels! 

Spend a Little Time in the Sunshine 

The easiest and cheapest way to give your baby a dose of vitamin D? Get some sun exposure! Keep in mind, a dose of sunshine is only recommended once a child has reached 6 months of age, when melanin production has had a chance to help protect your child’s skin from UV rays. If you want to celebrate your baby’s six-month birthday with a picnic, be sure to keep him protected with:

  • A baby hat with a wide brim to protect that cute face
  • Long-sleeved clothing to keep him covered
  • Baby sunscreen to ensure maximum sun protection

Take a Peek into Your Child’s Genetics 

Encoded in every child’s DNA is a whole world of possibilities—everything from his eye color to the shape of his earlobes. Did you know that our genetics can also play a part in the nutrients our bodies need to be their best? 

Some genes can affect whether an individual will need more or less of certain vitamins—like vitamin D to ensure healthy growth and development. Taking a look into that secret code written in your child’s genes can clue you into if your child will need extra care in the vitamin D department. 

Make Infant Nutrition as Easy as (Vitamins) ABC with SneakPeek Traits 

When you’re pregnant, you fantasize about your child’s eyes, hair, and smile, all the while hoping that whatever your child looks like, she’s as healthy as she can be. When you meet that little wonder, you know that her body’s health and wellness is in your loving care. What if you could get a little guidance into her body’s nutritional needs as predicted by her genetics?

Enter SneakPeek Traits.

SneakPeek Traits is a DNA test that offers you a look into your child’s unique genetic code. After your child is born, you can use SneakPeek Traits to discover insights about your child’s unique nutritional profile including:

  • Childhood/Baby BMI 
  • Vitamin levels for more than 9 key vitamins (including vitamin D)
  • Sleep habits
  • Bitter food sensitivity
  • And so much more!

Each genetic report comes with personalized advice for your baby’s individual traits, so you can explore a whole new way to bring health and wellness into your child’s life.  

Discover how you can help your child live her best life by knowing her unique nutritional profile with SneakPeek Traits



La Leche League International. Vitamin D.

CDC. Vitamin D.

Parenting. Vitamin D Deficiency in Babies.

The Royal Children’s Hospital Melbourne. Vitamin D.

Harvard Health Publishing. Vitamin D and your health.

Mayo Clinic. Infant and Toddler Health: Vitamin D.,to%20prevent%20vitamin%20D%20deficiency.

Cleveland Clinic. Do Babies Really Need Vitamin D Supplements?

Healthline. How to Safely Get Vitamin D From Sunlight.

A Way with Words. Dar a Luz.,woman%20who%20is%20giving%20birth.

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SneakPeek aims to provide the most accurate and up-to-date information to help our readers make informed decisions regarding their health before, during, and after pregnancy. This article was written based upon trusted scientific research studies and/or articles. Credible information sources for this article are cited and hyperlinked.

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