Are your vitamin D levels low? An expert shares some symptoms to look out for

I rarely miss a day of taking my B12 vitamins — I need the energy. And I'm getting plenty of vitamin C intake through the fruits and vegetables I eat throughout the day. But where I, like many Americans, have dropped the ball is with vitamin D. That's a no-no. Vitamin D is incredibly important for our health, and we need it even more during winter when our sun exposure is reduced. Some 22% of Americans are deficient in the nutrient — and I'm among them, as I recently learned following a blood panel.

Compared with other vitamins, D is harder to get from diet alone. If you’re not a milk or mushroom enthusiast (I’m with you on that) or you don’t enjoy fish (another vitamin D source), you may not get enough.

Vitamin D, also known as the "sunshine vitamin" (yes, you can get it from sun exposure too!), is important for bone health, the immune system and even mood. If your vitamin D levels drop significantly, it could affect your mood, causing you to feel fatigued or depressed. A vitamin D deficit can also lead to muscle aches, weakness and even bone pain, which you should address immediately.

I spoke with Katherine Zeratsky, a registered dietitian at the Mayo Clinic, to find out what causes vitamin D levels to drop and what symptoms you should be on the lookout for so you know when it’s time to start taking a vitamin D supplement.

Why is vitamin D important?

Remember when Mom used to stress how important drinking milk is for your bones? There was a reason for that — milk is not only one of the best ways to consume calcium but also a good source of vitamin D, which is important for keeping your bones from becoming weak and brittle.

Having enough vitamin D helps your body absorb calcium from the foods you eat. You need a sufficient amount of vitamin D to help your body keep normal calcium and phosphorus levels, Zeratsky says, because these three nutrients work together to build and maintain your bones.

Additionally, vitamin D plays a role in muscle repair and contraction, she says. It also helps reduce inflammation and keeps your immune system working properly so your body can fight off infections.

How much vitamin D do you need to take each day?

The amount of vitamin D needed each day varies from person to person. However, the daily recommended dose to sustain vitamin D levels is 10 micrograms (mcg) for infants and 15 mcg for ages 1 through 70. After 71, the recommended dose is 20 mcg every day.

If you suspect that you're deficient, your doctor can help you determine whether you need to supplement and what your dosage should be. Zeratsky says that your care provider typically will prescribe a higher level of vitamin D for a specific amount of time to see if it neutralizes your levels. After that time frame — which could be a few months — your levels should be rechecked and the dosage amount should be adjusted based on your results.

What are some symptoms of low vitamin D?

You can be deficient in vitamin D and show zero symptoms — the only way to be certain is by getting levels checked, which can be done at your doctor's office, a wellness center, medical spa or a lab. A blood sample will be drawn and analyzed to see whether you have a vitamin D deficiency. Levels below 30 nanomoles per liter (nmol/L) are considered low, while 50 nmol/L and above is considered normal. But here are some symptoms you might experience if your body is low on the nutrient.

Muscle and bone pain

Low vitamin D levels can cause muscle weakness, cramps and bone pain. You'll generally feel muscle weakness in your upper arms, hips and thighs, according to Yale Medicine, which can cause you to waddle while walking. Muscle spasms, twitches and tremors are also a sign to look out for, and muscle pain in general.

Broken bones

A history of broken or fractured bones could also signify you're low in vitamin D. A long-term deficiency in vitamin D can lead to osteoporosis, a disease that causes bone density loss, which can increase the risk of fractures and broken bones. Osteoporosis itself can also cause bone pain.

Depression

Low levels of vitamin D have also been linked to depression, with studies finding that supplementing vitamin D helped reduce depressive symptoms in adults with depression. However, supplementation was only found useful in people without a severe vitamin D deficiency.

Fatigue

Feeling extra tired? It could be the lack of vitamin D you're getting. A clinical trial found that when given vitamin D3 supplements, people in the study felt less fatigued than before, as compared to the placebo group.

If you're experiencing any of the symptoms above, make an appointment with your doctor to have your labs checked.

What causes low vitamin D levels?

Vitamin D isn't available in many foods (I've listed some good sources below), so it may be harder to get your daily dose from the foods you eat. Most of your vitamin D comes from the sun, and the most common reason for reduced vitamin D levels is not getting enough of the sun's UV light exposure on your skin. Spending less time outside and wearing protective clothing can reduce the amount of vitamin D your skin makes and stores, Zeratsky says.

It may feel like a battle you can't win when it comes to protecting your skin from harmful UV rays versus getting an adequate amount of vitamin D. However, you only need to spend about 10 minutes outdoors (after applying sunscreen, of course) a few days a week to benefit from the sun — wearing sunscreen shouldn't largely impact how much vitamin D you get. If you're still not comfortable exposing your delicate skin to the sun even after applying sunscreen, there are also ways to supplement.

Zeratsky says there may also be underlying medical causes for low vitamin D, such as kidney disease, a failure to absorb fat from food, or certain medications—for instance, blood pressure medications, cholesterol-lowering drugs and steroids.

Who is most at risk for low vitamin D?

Anyone can be deficient in vitamin D, but some people tend to be more affected than others. This includes anyone who spends most of their time indoors because they're not getting an adequate amount of sunlight each day.

Older adults (over 65) have a higher risk of being deficient, Zeratsky says, because their skin has a harder time efficiently synthesizing vitamin D compared with younger people, so they don't receive the same vitamin D benefits from the sun. People with darker skin are also more at risk because melanin in the skin blocks the absorption of vitamin D from the sun.

Breastfed infants also risk not getting enough vitamin D through milk, compared with formula-fed babies, and will often need to take vitamin D drops to make sure they don't become deficient. Ask your child's pediatrician if they have some on hand that you can give your baby, or if they have a recommendation for what you can buy.

Are there any risk factors if vitamin D levels stay low?

Chronically low vitamin D can result in weak bones at any age. In infants and young children, developing bones can become misshapen or deformed, causing rickets, a softening and weakening of bones. For adults, chronically low vitamin D may cause bones to break easier than usual. Adults may also develop osteoporosis, which can result in a stooped posture.

A long-term vitamin D deficiency can lead to malfunction of the parathyroid, which is responsible for regulating calcium levels in the blood. This can lead to further bone and muscle problems.

Can you get too much vitamin D?

While you typically hear about people having a vitamin D deficiency, it's possible to also have what's called vitamin D toxicity, meaning you have too much vitamin D in your system. It's rare and is usually caused by large doses of vitamin D supplements, rather than sun exposure.

If severe, it can cause a buildup of calcium in your blood and lead to calcium stones due to kidney problems, Zeratsky notes.

How can you increase your vitamin D levels?

While the most well-known way to increase your vitamin D is through sun exposure, you may be hesitant if you're super protective of your skin — and that's OK. There are other ways to up those levels, like eating foods that are vitamin D-rich such as fatty fish. Some foods may also be fortified, which means vitamin D has been added to the food.

Foods that are naturally high in vitamin D:

• Mushrooms

• Eggs

• Tuna

• Salmon

• Tilapia

Foods that are fortified with vitamin D:

• Milk

• Yogurt

• Orange juice (also great for vitamin C)

• Some cheeses, like American

• Some cereals and oatmeals

You can also talk to your doctor to see how much vitamin D you need to take and get a supplement dose that matches your needs. The recommended amount varies, depending on your age, current vitamin D level and lifestyle, Zeratsky says. They'll likely recommend vitamin D3 since it's what the body naturally produces, and it's more effective than D2 and can raise your vitamin D levels quickly.

If you've already been diagnosed with a vitamin D deficiency and are looking for options to increase your levels, here are some of the best vitamin D supplements tested by a registered dietitian. If you choose to buy something off this list, make sure it's labeled "third-party tested." This ensures that it has the right amount of micrograms stated on the label and that it doesn't contain any ingredients not listed on the label.

A note on supplements

Supplements are regulated far less stringently by the FDA than medications, with little oversight on safety or effectiveness before they go to market. Supplements may also interact with other medications and aren't appropriate for all populations or health conditions. While our health writers personally select and test products that are evidence-based, it's important to talk with your health care provider before adding a dietary supplement to your routine.