Vitamin D deficiency is common and can develop without obvious symptoms. When levels become too low, some people may experience bone or muscle pain, muscle weakness, tiredness, or other health concerns. Because these symptoms can have many different causes, a blood test can help determine whether vitamin D deficiency is present.
If you have persistent fatigue, muscle weakness, bone or muscle pain, or risk factors for vitamin D deficiency, contact MVR Diagnostic Clinic to discuss whether a vitamin D blood test is appropriate for you.
Vitamin D is a fat-soluble vitamin that helps the body absorb calcium and supports normal bone health, muscle function, and other biological processes. The body can produce vitamin D when the skin is exposed to sunlight. It can also be obtained from certain foods and dietary supplements.
Vitamin D deficiency occurs when the body's vitamin D stores are not sufficient for its needs. Severe deficiency can affect bone mineralization and may lead to conditions such as osteomalacia in adults and rickets in children. It is important to distinguish vitamin D deficiency from simply having a lower-than-ideal vitamin D result. The interpretation of vitamin D levels depends on the laboratory, clinical situation, and reason for testing.
Vitamin D deficiency can develop for several reasons. It is not always caused by a lack of sunlight.
The skin produces vitamin D when exposed to ultraviolet B radiation from sunlight. People who spend little time outdoors may produce less vitamin D. This can include people who work indoors, have limited mobility, or regularly cover most of their skin. However, sun exposure should not be increased excessively just to raise vitamin D levels because ultraviolet radiation also increases the risk of skin cancer.
Higher levels of melanin in the skin can reduce the amount of vitamin D produced in response to sunlight. This can increase the likelihood of low vitamin D levels, particularly when combined with limited sun exposure.
Only a relatively small number of foods naturally contain significant amounts of vitamin D. People who do not consume enough vitamin D-containing or fortified foods may have a higher risk of deficiency.
Because vitamin D is fat-soluble, conditions that interfere with fat absorption can also affect vitamin D absorption.
These may include:
People with obesity may have a higher risk of low vitamin D levels and may require different management depending on their individual circumstances.
Certain weight-loss procedures can affect nutrient absorption and may increase the risk of vitamin D deficiency.
The skin's ability to produce vitamin D decreases with age. Older adults may therefore have a higher risk of inadequate vitamin D levels.
Mild vitamin D deficiency may cause no noticeable symptoms.
When deficiency becomes more significant, symptoms may include:
Severe deficiency can affect bone mineralization. In adults, this can lead to osteomalacia, which may cause bone pain and muscle weakness. However, fatigue and muscle pain are very common symptoms with many possible causes. They should not automatically be attributed to vitamin D deficiency without appropriate evaluation.
Vitamin D deficiency can occur alongside fatigue, but tiredness alone does not prove that vitamin D is low. Fatigue may also be associated with anemia, thyroid problems, sleep disorders, infections, nutritional deficiencies, stress, and many other conditions. If fatigue persists or occurs together with weakness, muscle pain, or other symptoms, your healthcare provider may recommend appropriate blood tests.
For another possible cause of persistent fatigue and weakness, see MVR's Anemia Profile Test guide .
Yes, significant vitamin D deficiency can be associated with muscle weakness and muscle discomfort. However, muscle pain can result from many conditions, including injuries, overuse, electrolyte problems, medication effects, and other nutritional deficiencies. A vitamin D blood test can help determine whether low vitamin D may be contributing to the symptoms.
Yes. Vitamin D helps the body absorb calcium, which is essential for maintaining healthy bones. Severe vitamin D deficiency can impair bone mineralization. In adults, prolonged deficiency can cause osteomalacia, resulting in weak bones and bone pain. In children, severe deficiency can cause rickets. This is one reason vitamin D is particularly important during periods of bone growth and throughout adulthood.
Some people are more likely to have low vitamin D levels.
Risk factors include:
Having a risk factor does not automatically mean that you are deficient.
A vitamin D blood test measures the amount of 25-hydroxyvitamin D, also written as 25(OH)D, in the blood. This is the main blood marker used to assess vitamin D status. Results may be reported in either ng/mL or nmol/L.
The test can help determine whether vitamin D levels are low and whether further evaluation or treatment may be appropriate. Vitamin profile blood test can be used to assess vitamin levels as part of laboratory health testing.
Vitamin D results should be interpreted according to the laboratory's reference range and the patient's clinical circumstances.
As a general reference, NIH guidance states that:
However, these numbers should not be treated as universal treatment targets for every person. The 2024 Endocrine Society guideline also notes that specific blood-level thresholds for preventing disease have not been established for healthy populations. It recommends against routine 25(OH)D screening in generally healthy adults without an established indication for testing.
A vitamin D blood test can indicate whether your circulating 25(OH)D level falls within, below, or above the laboratory's reference range.
The result can help a healthcare professional determine whether:
The result should be interpreted alongside symptoms, medical history, diet, medications, and other laboratory findings.
Fasting is not usually required for a vitamin D test alone. However, preparation requirements can differ when vitamin D is being tested as part of a larger blood-test panel. For example, other tests performed during the same appointment may have specific fasting requirements.
Before your appointment, confirm the preparation instructions with the diagnostic center. Do not stop prescribed medication or supplements unless your healthcare professional tells you to.
Yes. Vitamin D may be assessed alongside other laboratory tests when a doctor is investigating fatigue, bone health, nutritional deficiencies, or another health concern.
Depending on the clinical situation, testing may include:
The appropriate combination depends on the person's symptoms and medical history.
These terms are sometimes used differently by different laboratories and healthcare professionals. A low vitamin D result does not automatically mean that a person has a disease requiring high-dose treatment.
The clinical interpretation depends on the actual result, the laboratory's reference range, symptoms, risk factors, and whether there is an established medical indication for treatment.
This is particularly important because guidelines have changed over time. The 2024 Endocrine Society guideline does not recommend routine vitamin D screening in generally healthy adults without an established indication.
Diet can contribute to vitamin D intake, although relatively few foods naturally contain substantial amounts.
Sources include:
The amount of vitamin D varies considerably between foods and products. For people who cannot obtain enough vitamin D from food and sunlight, a healthcare professional may recommend supplementation based on individual needs.
The skin can produce vitamin D from sunlight, but the amount produced varies.
Factors include:
Because excessive ultraviolet exposure increases skin cancer risk, deliberately spending prolonged periods in the sun is not recommended as a strategy for treating vitamin D deficiency.
Treatment depends on the severity of deficiency and why it developed.
A healthcare professional may recommend vitamin D supplementation when deficiency is confirmed or when supplementation is otherwise clinically indicated. The dose and duration depend on the individual situation. Do not assume that taking a very high dose is better. Vitamin D is fat-soluble, and excessive intake can cause toxicity.
If low vitamin D is related to poor absorption, a gastrointestinal condition, medication, or another health issue, treating or managing the underlying problem may be an important part of care.
Increasing foods that contain vitamin D may help support adequate intake, depending on your diet and individual requirements.
A healthcare professional may recommend repeat testing in selected patients to assess the response to treatment.
Routine repeat testing is not necessarily required for everyone.
Yes. Vitamin D toxicity is generally caused by excessive intake of vitamin D supplements rather than normal exposure to sunlight.
Excess vitamin D can cause high calcium levels in the blood, which may lead to symptoms such as:
NIH guidance notes that blood levels above 125 nmol/L (50 ng/mL) can be associated with adverse effects, although toxicity and treatment decisions require clinical interpretation. Avoid taking high-dose vitamin D supplements without medical advice.
A vitamin D test may be appropriate when a healthcare professional has a specific reason to investigate vitamin D status.
Possible reasons include:
Routine testing is not recommended for every healthy person. The Endocrine Society's 2024 guideline specifically recommends against routine 25(OH)D testing in healthy adults without an established indication.
Older adults may be more likely to develop low vitamin D levels because the skin becomes less efficient at producing vitamin D with age. Reduced outdoor activity can also contribute. However, supplementation and testing should still be based on individual needs rather than assuming that every older adult requires high-dose vitamin D.
The 2024 Endocrine Society guideline recommends daily, lower-dose supplementation rather than intermittent high-dose supplementation for adults aged 50 and older who have an indication for vitamin D treatment.
Vitamin D requirements during pregnancy should be discussed with an obstetrician or other qualified healthcare professional. The Endocrine Society's 2024 guideline suggests empiric vitamin D supplementation during pregnancy, while also recommending against routine 25(OH)D testing in pregnant people without another indication for testing.
Pregnant people should not start high-dose vitamin D treatment independently. Prenatal supplements and additional vitamin D should be discussed with the healthcare professional managing the pregnancy.
Vitamin D is particularly important during childhood because it supports normal bone development. Severe deficiency in children can cause rickets, in which bones become soft and weak.
Children have different nutritional requirements from adults, so supplements and testing should be guided by a pediatrician.
The effects depend on the severity and duration of deficiency.
Significant prolonged deficiency can contribute to:
Not every low vitamin D result causes symptoms or complications. The importance of treatment depends on the individual clinical situation.
Fatigue, weakness, and other nonspecific symptoms can occur with several nutritional deficiencies.
For example, vitamin B12 deficiency can cause fatigue, weakness, and neurological symptoms, while iron deficiency can contribute to anemia and tiredness.
If you have unexplained fatigue or multiple symptoms, it may be more useful to discuss a broader assessment with your healthcare provider rather than focusing on a single nutrient.
Consider medical advice if you have:
A healthcare professional can determine whether vitamin D testing is appropriate and whether other blood tests are needed.
Vitamin D deficiency can affect bone and muscle health, but symptoms alone cannot confirm a deficiency. A 25-hydroxyvitamin D blood test is the main laboratory test used to assess vitamin D status. At the same time, routine vitamin D testing is not recommended for every healthy adult. Testing is most useful when there is a clinical reason to investigate vitamin D status.
If you have persistent fatigue, muscle weakness, bone pain, or risk factors for vitamin D deficiency, contact MVR Diagnostic Clinic to discuss whether a vitamin profile blood test is appropriate for you.
Significant vitamin D deficiency can cause bone pain, muscle weakness, and muscle discomfort. Some people may also experience fatigue, although fatigue has many possible causes.
The main blood test is 25-hydroxyvitamin D, also known as 25(OH)D. It measures the form of vitamin D used to assess vitamin D status.
NIH guidance states that levels below 30 nmol/L (12 ng/mL) are too low, while 50 nmol/L (20 ng/mL) or above is adequate for most people for bone and overall health. However, results should be interpreted using the laboratory's reference range and the individual's clinical circumstances.
Fasting is generally not required for a vitamin D test alone. If other tests are being performed at the same time, however, fasting may be required for those tests.
Yes. Significant vitamin D deficiency can cause muscle weakness and may also be associated with muscle discomfort.
Yes. Treatment may involve vitamin D supplementation, dietary changes, and addressing an underlying cause such as impaired absorption. The appropriate dose depends on the individual's circumstances.
Yes. Some people with low vitamin D levels have no obvious symptoms. Testing is therefore based on clinical indications rather than symptoms alone.