Everything You Need to Know About Vitamin D Deficiency

A woman lays against a wall with fractured sunlight hitting her.
  • Also known as the ‘sunshine vitamin’, vitamin D is produced by the body when the skin is exposed to sunlight. Vitamin D can also be found in different food groups.

  • A vitamin D deficiency means that an individual does not have an adequate level of this micronutrient in their body, which could cause several health problems.

  • Although not everyone will experience symptoms, some common signs of vitamin D deficiency include fatigue, bone pain, and becoming ill regularly.

Vitamin D is a group of fat-soluble vitamins that are crucial to several processes in the body.

There are two main types of this vitamin – D2 and D3. While vitamin D2 is primarily obtained from food sources, D3 is produced by the body when the skin is exposed to sunlight.

According to the National Institutes of Health (NIH), approximately one billion people worldwide have low vitamin D levels. This figure accounts for one in every four adult Americans.

Vitamin D deficiency is one of the most common nutritional deficiencies in the world.

This vitamin is mostly responsible for bone health and immune system support, so people with lower vitamin D levels may experience bone-related health problems and be more susceptible to viruses and infections.

What is Vitamin D Deficiency?

Vitamin D deficiency occurs when an individual does not have enough of this vitamin in their body to function optimally. It means that a person is not getting enough vitamin D from exposure to sunlight or through their dietary intake.

A deficiency may also mean they have problems absorbing vitamin D, which can be caused by various health conditions.

To diagnose a vitamin D deficiency, a healthcare professional will run a blood test to determine its level in the body.

What health problems does a vitamin D deficiency cause?

As vitamin D plays a role in several important functions in the body, a lack of this nutrient can result in potential health issues, including:

  • Weakened bones: Vitamin D promotes and maintains normal bone development by aiding the absorption of calcium and phosphorus in the body. A lack of this essential vitamin can result in a range of issues that affect the strength and health of the bones.

  • Increased risk of osteoporosis: A deficiency may lead to osteoporosis, which is an age-related condition where the bones become weakened.

  • Muscle weakness: A vitamin D deficiency can result in problems with mobility, function, and strength in the muscles because it plays an important role in how the muscles work

  • Increased risk of falls or fractures: As bones are weaker due to a lack of calcium absorption, people have a higher risk of falling and breaking their bones.

  • Cardiovascular disease: Scientists have found a link between vitamin D deficiencies and the risk of diseases such as high blood pressure, stroke, and heart disease.

  • Mental health problems: Vitamin D deficiencies have been linked to mood disorders, including seasonal affective disorder (SAD) and depression.

What causes a vitamin D deficiency?

There are certain risk factors that make some individuals more likely to develop a vitamin D deficiency, including:

A vitamin d supplement capsule is held up to the sky, with sunlight shining through it.

Inadequate sun exposure

As vitamin D is produced in the body as a result of sunlight exposure, limited time in the sun may lead to lower levels of this vitamin.

Lack of dietary intake

If an individual does not eat enough vitamin D-rich foods, they may not have adequate levels of this nutrient.

Key Point: Foods That Contain Vitamin D

Some important sources of vitamin D in foods include:

  • Fatty fish
  • Egg yolks
  • Fortified foods like milk and cereals
  • Plant-based milk alternatives
  • Cod liver oil

Darker skin tones

Individuals with darker skin tones might not get enough sun exposure because the melanin in their skin acts as a natural barrier against sunlight.


Older adults are known to have an increased risk of this deficiency because their bodies may struggle to convert sunlight into vitamin D. They may also not get enough sunlight exposure due to mobility issues.


People living in regions with less intense sunlight may be at risk for a vitamin D deficiency.

Health conditions

Certain disorders, such as celiac disease, inflammatory bowel disease (IBD), or exocrine pancreatic insufficiency (EPI), can prevent the body from efficiently absorbing vitamin D.

An older man holds his head to his cane as he sits in a dark room.

Vitamin D levels explained

Vitamin D is measured in the blood in nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL). According to the NIH, vitamin D levels in the blood can be interpreted as follows:

Level of vitamin D


50 nmol/L (20 ng/mL) or above

Adequate for most people.

Below 30 nmol/L (12 ng/mL)

Too low and could indicate a deficiency.

Above 125 nmol/L (50 ng/mL)

Too high and may cause health problems.

What are the Symptoms of a Vitamin D Deficiency?

A vitamin D deficiency may result in certain symptoms, but it is also possible to have no noticeable symptoms from a lack of this nutrient.

It's worth noting that the symptoms below may be indicative of other health conditions. However, if these symptoms sound familiar, it's advised to consult with a healthcare professional.


Feeling overly tired and having a general lack of energy may be a symptom of a vitamin D deficiency.

It has been found that older adults with a deficiency of this vitamin experienced fatigue.

Children with low levels of vitamin D may have poor sleep quality and shorter periods of sleep, which may lead to fatigue.

Research has also discovered that taking a vitamin D supplement may reduce fatigue and lack of energy. A study on female nurses revealed that participants felt less tired with vitamin D supplementation.

A woman lays on a couch and closes her eyes.

Mental health problems

A lack of vitamin D in the body can lead to mental health symptoms like depression and anxiety, especially in older adults.

Although more research is needed, this is likely because a link has been found between vitamin D and mood. One trial identified that people who had anxiety and depression exhibited low levels of vitamin D in their bodies.

Pregnant women with sufficient vitamin D in their bodies may also experience reduced anxiety, possibly preventing postpartum depression.

Getting sick regularly

As vitamin D is thought to significantly impact immune function, it’s possible that having low levels of this vitamin may mean you fall ill more often.

This may be because vitamin D interacts with the cells in the body that are responsible for addressing infections.

Common illnesses associated with vitamin D deficiency include respiratory infections, colds, or flu. A link between a lack of vitamin D, bronchitis, and pneumonia has also been discovered.

Slow-healing wounds

Some research has discovered a connection between vitamin D and healing. It is suggested that vitamin D increases the body’s production of certain compounds that are responsible for producing new skin during healing processes.

Vitamin D is also thought to play a role in regulating inflammation, which might also impact healing. For this reason, people with a vitamin D deficiency may find that wounds and sores heal slower than normal.

One study found that people with severe vitamin D deficiency who also had diabetes experienced slower healing wounds and elevated levels of inflammation.

Muscle and bone pain

As mentioned above, vitamin D plays a vital role in how calcium is absorbed.

Calcium is crucial for bone growth and maintenance. So, without enough vitamin D, some individuals might experience bone and muscle pain.

It has also been discovered that people with arthritis and chronic pain conditions typically had lower levels of vitamin D.

Hair loss

Although research into the link between vitamin D and hair loss is limited, there is some evidence that there could be a connection.

Low vitamin D levels may lead to a disease that causes hair loss called alopecia areata. However, studies suggest that people with alopecia areata who take vitamin D supplements may experience increased hair growth.

Weight gain

Obesity is a known risk factor for vitamin D deficiency. Vitamin D is a fat-soluble vitamin, meaning it is stored in body fat before it is released.

It is believed that excess body fat may mean too much vitamin D is stored in the body rather than being circulated.

A recent study found that there may be some link between low vitamin D levels in those with excess belly fat and excessive body weight.

Although more research is needed, there is some evidence that a lack of vitamin D may contribute to weight gain.

Should I Take Vitamin D Supplements?

People with a deficiency may be advised by their healthcare provider to take dietary supplements containing vitamin D.

You may also want to take a vitamin supplement containing vitamin D if you are at risk of developing a deficiency based on the factors outlined above.

It's important to consult with a healthcare provider before starting a vitamin D supplement, as an excess of this nutrient in your body can cause serious health problems.

A woman holds vitamin d supplements in her hand, with a bowl of nuts and a green smoothie nearby.

How to Get More Vitamin D

To ensure you are getting enough vitamin D and to avoid a deficiency, consider increasing your exposure to sunlight for up to 30 minutes per day.

You can also start eating more foods rich in vitamin D, such as those described above.

Key Point: How Much Vitamin D Do I Need?

According to the NIH, the recommended dietary allowance for vitamin D in International units (UI) is:

  • Birth to 12 months: 400 IU
  • Children between one to three years: 600 UI
  • Teenagers between 14 and 18 years: 600 UI
  • Adults between 19 and 70 years: 600 UI
  • Adults 71 and older: 800 UI

Where Can I Learn More About Vitamin D Deficiency Symptoms?

Experience the convenience of expert health guidance and support for your vitamin D deficiency through LifeMD's online portal.

With a telehealth consultation, you can access professional medical assistance without leaving the comfort of your home.

A healthcare professional can help diagnose a vitamin D deficiency using a local partner lab that’s convenient for you.

Head over to the LifeMD website to book your appointment today.

Shanta Williams, APRN

Shanta is a board-certified, multi-state NP who has worked in healthcare for over 14 years. She earned her M.S. in Family Nurse Practitioning. In 2020, she was one of the first Nurse Practitioners to assist with the COVID-19 outbreak in New York.

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This article is intended for informational purposes only and should not be considered medical advice. Consult a healthcare professional or call a doctor in the case of a medical emergency.

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