Vitamin D Deficiency
What is Vitamin D deficiency?
Vitamin D deficiency happens when your body does not have enough vitamin D to support healthy bones and muscles. Vitamin D is a nutrient your body makes when your skin is exposed to sunlight. You also get smaller amounts from foods like fatty fish, egg yolks, and fortified milk. Your body needs vitamin D to absorb calcium and maintain strong bones.
When vitamin D levels drop too low, your bones can become thin, brittle, or misshapen. In children, severe deficiency causes rickets, a condition where bones soften and bend. In adults, it causes osteomalacia, which leads to bone pain and muscle weakness. Many people have low vitamin D levels without knowing it, especially those who spend most of their time indoors.
Vitamin D deficiency affects people of all ages across the world. It is especially common in older adults, people with darker skin, and those who live in northern climates with less sunlight. The good news is that testing and treatment are straightforward, and most people can restore healthy levels with supplements and lifestyle changes.
Symptoms
- Bone pain or tenderness
- Muscle weakness and aches
- Fatigue and low energy
- Mood changes or feeling down
- Frequent infections or slow wound healing
- Hair loss
- Back pain
Many people with vitamin D deficiency have no obvious symptoms, especially in the early stages. The condition often goes unnoticed until blood testing reveals low levels or bone problems develop.
Concerned about Vitamin D deficiency? Check your levels.
Screen for 1,200+ health conditions
Causes and risk factors
The most common cause of vitamin D deficiency is limited sun exposure. Your skin makes vitamin D when exposed to ultraviolet B rays from sunlight. People who spend most of their time indoors, live in northern latitudes, or always wear sunscreen may not produce enough. Darker skin contains more melanin, which reduces the skin's ability to make vitamin D from sunlight. Older adults also have reduced ability to produce vitamin D through their skin.
Diet plays a smaller but important role. Few foods naturally contain vitamin D, so people who do not eat fortified foods or fatty fish may not get enough. Medical conditions that affect fat absorption, such as Crohn's disease or celiac disease, can prevent your body from absorbing vitamin D properly. Obesity can also lower vitamin D levels because the vitamin gets trapped in fat cells. Certain medications, including some cholesterol drugs and seizure medications, can interfere with vitamin D metabolism.
How it's diagnosed
Vitamin D deficiency is diagnosed through a blood test that measures 25-hydroxyvitamin D levels. This is the most accurate way to assess your vitamin D status. Your doctor will look at your test results along with your symptoms and medical history. Levels below 20 nanograms per milliliter are generally considered deficient, while levels between 20 and 30 are considered insufficient.
Specialized vitamin D testing may be needed to fully evaluate your vitamin D status. Talk to your doctor about which tests are right for you based on your symptoms and risk factors. Your doctor may also check your calcium and phosphorus levels, as these work closely with vitamin D in your body.
Treatment options
- Take vitamin D supplements as directed by your doctor, typically 1,000 to 4,000 IU daily
- Spend 10 to 30 minutes in midday sun several times per week without sunscreen, balancing skin cancer risk
- Eat more vitamin D rich foods like salmon, mackerel, sardines, egg yolks, and fortified milk or cereals
- Maintain a healthy weight through balanced nutrition and regular physical activity
- Get regular blood tests to monitor your vitamin D levels and adjust treatment
- Treat underlying conditions that affect vitamin D absorption, such as digestive disorders
- Consider higher prescription doses of vitamin D if you have severe deficiency
Frequently asked questions
The first signs are often subtle and include fatigue, muscle weakness, and bone pain. Many people feel tired or run down without realizing vitamin D is the cause. Some people experience mood changes or get sick more often than usual. However, many people have no noticeable symptoms until deficiency becomes severe.
Most people see improvement within a few weeks of starting supplements, but it can take 2 to 3 months to restore healthy levels. Your doctor will likely retest your blood after 8 to 12 weeks to check your progress. Severe deficiency may require higher doses and longer treatment. Maintaining healthy levels requires ongoing attention to sun exposure, diet, and supplements.
Yes, but vitamin D toxicity is rare and usually happens only with very high supplement doses over time. Symptoms include nausea, vomiting, weakness, and kidney problems. Your body cannot make too much vitamin D from sun exposure because it self-regulates production. Toxicity typically occurs only with supplement doses above 10,000 IU daily taken for months.
People with darker skin need more sun exposure to produce the same amount of vitamin D as those with lighter skin. Older adults, people who are homebound, and those living in northern climates are also at higher risk. People with obesity, digestive disorders, or kidney disease have increased risk. Breastfed infants and people who avoid animal products may also be at risk.
For some people, regular sun exposure is enough to maintain healthy levels. About 10 to 30 minutes of midday sun on bare arms and legs several times per week may be sufficient. However, many factors affect vitamin D production, including skin color, age, latitude, and season. Most people need some combination of sun exposure, food sources, and supplements.
Fatty fish like salmon, mackerel, and sardines contain the most natural vitamin D. A 3-ounce serving of cooked salmon provides about 570 IU. Cod liver oil is extremely high in vitamin D, with over 1,300 IU per tablespoon. Egg yolks, beef liver, and fortified foods like milk, orange juice, and cereals also provide vitamin D.
Vitamin D3 is generally considered more effective at raising and maintaining blood levels of vitamin D. Your body makes D3 naturally when your skin is exposed to sunlight. D2 comes from plant sources and is sometimes used in prescription medications. Most experts recommend D3 supplements unless you have a specific reason to use D2.
Low vitamin D levels are associated with obesity, but the relationship is complex. Obesity can cause vitamin D deficiency because the vitamin gets stored in fat tissue. Some research suggests that low vitamin D may affect metabolism and appetite regulation. However, taking vitamin D supplements alone is not proven to cause weight loss.
Research shows a connection between low vitamin D levels and mood disorders, including depression and seasonal affective disorder. Vitamin D receptors are found throughout the brain, and the nutrient may play a role in mood regulation. Some studies suggest that vitamin D supplements may help improve mood in people with deficiency. However, supplements are not a replacement for mental health treatment.
Yes, vitamin D is a fat-soluble vitamin, meaning it absorbs best when taken with a meal containing some fat. Taking your supplement with breakfast, lunch, or dinner helps your body absorb more of the vitamin. You do not need a high-fat meal, just some dietary fat like nuts, avocado, or olive oil. Consistency matters more than the specific meal.