Vitamin D, 25-Hydroxy, Total, Immunoassay Most Popular

The Vitamin D, 25-Hydroxy, Total, Immunoassay test contains 1 test with 2 biomarkers.

Brief Description: The Vitamin D 25-Hydroxy Total test, also known as a 25(OH)D test, is a blood test that measures the levels of total 25-hydroxyvitamin D in the body. It assesses the overall vitamin D status and helps evaluate the adequacy of vitamin D levels for proper bone health and overall well-being. Vitamin D plays a crucial role in calcium absorption, bone metabolism, immune function, and other essential processes in the body.

Also Known As: 25-hydroxyvitamin D Test, Vitamin D 25-Hydroxyvitamin Test 

Collection Method: Blood Draw 

Specimen Type: Serum 

Test Preparation: Fasting preferred, but not required. 

When is a Vitamin D test ordered?

A Vitamin D 25-Hydroxy Total test may be ordered in several situations to assess a patient's vitamin D levels:

1. Evaluation of Bone Health: The test is often ordered when there is a suspicion of vitamin D deficiency or to evaluate bone health. It helps diagnose conditions like osteoporosis, rickets, or osteomalacia associated with inadequate vitamin D levels.

2. Monitoring Vitamin D Supplementation: For individuals taking vitamin D supplements, the test is ordered to monitor the effectiveness of supplementation and ensure that the desired vitamin D levels are being achieved.

3. Assessment of Absorption Disorders: The Vitamin D 25-Hydroxy Total test is used to evaluate vitamin D status in individuals with malabsorption disorders, gastrointestinal disorders, or conditions that may affect vitamin D absorption.

4. Evaluation of Chronic Conditions: Some chronic diseases or conditions, such as kidney disease, liver disease, or certain autoimmune disorders, may impact vitamin D metabolism. The test helps assess vitamin D levels in these cases.

What does a Vitamin D blood test check for? 

Vitamin D is a group of chemicals that are necessary for the healthy development and growth of bones and teeth. The level of vitamin D in the blood is determined by this test. 

Vitamin D is tested in the blood in two forms: 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D. The primary form of vitamin D found in the blood is 25-hydroxyvitamin D, which is a relatively inactive precursor to the active hormone 1,25-dihydroxyvitamin D. 25-hydroxyvitamin D is routinely evaluated to assess and monitor vitamin D status in humans due to its longer half-life and higher concentration. 

Vitamin D's major function is to assist balance calcium, phosphorus, and magnesium levels in the blood. Vitamin D is necessary for bone growth and health; without it, bones become fragile, misshapen, and unable to mend themselves properly, leading to disorders such as rickets in children and osteomalacia in adults. Vitamin D has also been proven to influence the growth and differentiation of a variety of other tissues, as well as to aid in immune system regulation. Other illnesses, such as autoimmune and cancer, have been linked to vitamin D's other roles. 

According to the Centers for Disease Control and Prevention, two-thirds of the US population has adequate vitamin D, while one-quarter is at risk of inadequate vitamin D and 8% is at risk of insufficiency, as defined by the Institute of Medicine's Dietary Reference Intake. 

The elderly or obese, persons who don't receive enough sun exposure, people with darker skin, and people who take certain drugs for lengthy periods of time are all at risk of insufficiency. Adequate sun exposure is usually defined as two intervals of 5-20 minutes each week. Vitamin D can be obtained through dietary sources or supplements by people who do not get enough sun exposure. 

Sample Ulta Lab Tests View of Vitamin D 25-Hydroxy Total Test Results

Sample Quest Result Report View of Vitamin D 25-Hydroxy Total Test Results

Lab tests often ordered with a Vitamin D test: 

Since Vitamin D influences or is influenced by various metabolic processes, other tests may be ordered alongside it to gain a comprehensive view of an individual's health status or to determine the cause or consequences of Vitamin D deficiency. Here are some of those tests:

1. Calcium:

   • Purpose: Vitamin D plays a significant role in calcium absorption and bone health.
   • Why Is It Ordered: To check for abnormalities in calcium levels that might be associated with a Vitamin D deficiency or excess, which could affect bone health and other physiological functions.

2. Phosphorus/Phosphate:

   • Purpose: Along with calcium, phosphorus is a critical component of bone health, and Vitamin D is important for its regulation.
   • Why Is It Ordered: To assess bone metabolism and renal function, especially if a Vitamin D deficiency or excess is suspected to be impacting these areas.

3. Parathyroid Hormone (PTH):

   • Purpose: PTH helps regulate calcium levels in the blood, and its secretion is influenced by Vitamin D levels.
   • Why Is It Ordered: To investigate parathyroid function and differentiate between primary hyperparathyroidism and secondary hyperparathyroidism, which may result from a Vitamin D deficiency.

4. Magnesium:

   • Purpose: Magnesium is involved in Vitamin D metabolism; a deficiency can affect Vitamin D levels and function.
   • Why Is It Ordered: To rule out magnesium deficiency as a cause of low Vitamin D or when symptoms such as muscle weakness or seizures are present, which can be related to both magnesium and Vitamin D deficiencies.

5. Alkaline Phosphatase (ALP):

   • Purpose: ALP can be elevated in conditions affecting the bones or liver.
   • Why Is It Ordered: To evaluate bone metabolism, particularly in cases where Vitamin D deficiency is suspected to be affecting bone turnover and health.

6. 25-Hydroxyvitamin D3 and D2 Levels:

   • Purpose: These are the two forms of Vitamin D that are often measured to understand the contribution of each form to the total Vitamin D level.
   • Why Is It Ordered: To distinguish between the sources of Vitamin D (D3 from sunlight and diet, D2 from some plants and supplements) and to guide supplementation and treatment effectively.

7. Kidney Function Tests (Creatinine, Blood Urea Nitrogen):

   • Purpose: Since the kidney is involved in converting 25-hydroxyvitamin D to its active form, kidney function is important for Vitamin D metabolism.
   • Why Is It Ordered: To evaluate whether kidney disease might be affecting Vitamin D metabolism, especially in the conversion of 25-hydroxyvitamin D to its active form, 1,25-dihydroxyvitamin D.

8. 1,25-Dihydroxyvitamin D:

   • Purpose: This is the active form of Vitamin D, which is produced in the kidneys.
   • Why Is It Ordered: In certain conditions, such as kidney disease or granulomatous diseases like sarcoidosis, measuring the active form of Vitamin D can provide more specific information about Vitamin D status and metabolism.

The decision to order these tests is typically based on the initial Vitamin D test results, the presence of symptoms or conditions related to Vitamin D deficiency or excess, and the overall clinical assessment of the patient. They help in developing a comprehensive understanding of the patient's bone health, the cause of Vitamin D imbalance, and in monitoring the effectiveness of Vitamin D supplementation or treatment.

Conditions where a Vitamin D test is recommended:

A Vitamin D 25-Hydroxy Total test is commonly ordered for:

1. Vitamin D Deficiency: The test helps diagnose and monitor vitamin D deficiency, which can lead to conditions such as rickets in children and osteomalacia or osteoporosis in adults.

2. Osteoporosis and Osteopenia: Vitamin D deficiency is associated with a higher risk of developing osteoporosis or osteopenia, conditions characterized by reduced bone density.

3. Malabsorption Disorders: Individuals with malabsorption disorders, such as celiac disease, Crohn's disease, or cystic fibrosis, may have impaired absorption of vitamin D and require testing to assess vitamin D levels.

How does my healthcare provider use a Vitamin D test? 

Healthcare providers use the results of a Vitamin D 25-Hydroxy Total test to:

1. Diagnose Vitamin D Deficiency: Abnormal test results indicating low vitamin D levels help healthcare providers diagnose and evaluate the severity of vitamin D deficiency.

2. Guide Treatment and Supplementation: Based on the test results, healthcare providers can recommend appropriate vitamin D supplementation, dosage, or dietary changes to address deficiencies and improve vitamin D levels.

3. Monitor Treatment Response: Regular testing allows healthcare providers to monitor the effectiveness of vitamin D supplementation or treatment interventions and make adjustments as needed.

By effectively utilizing the results of a Vitamin D 25-Hydroxy Total test, healthcare providers can assess vitamin D status, diagnose deficiencies, and implement interventions to improve bone health, overall well-being, and mitigate associated risks.

What do my Vitamin D results result mean? 

Even though vitamin D techniques differ, most laboratories use the same reference intervals. Because toxicity is uncommon, researchers have focused on the lower limit and what cut-off for total 25-hydroxyvitamin D shortage implies. 

A low blood level of 25-hydroxyvitamin D could indicate that a person isn't getting enough sunlight or dietary vitamin D to meet his or her body's needs, or that there's an issue with absorption from the intestines. Seizure medications, notably phenytoin, might occasionally interfere with the liver's generation of 25-hydroxyvitamin D. 

Vitamin D insufficiency has been linked to an increased risk of some malignancies, immunological illnesses, and cardiovascular disease. 

Excessive supplementation with vitamin pills or other nutritional source of vitamin D frequently results in a high level of 25-hydroxyvitamin D. 

Most Common Questions About the Vitamin D 25-Hydroxy test:

Understanding the Test

What is the Vitamin D 25-Hydroxy Total test?

The Vitamin D 25-Hydroxy Total test is a blood test that measures the total amount of vitamin D in your body.

What is the purpose of the Vitamin D 25-Hydroxy Total test?

The test is used to determine if your body has too much or too little vitamin D. It can help diagnose or monitor conditions like vitamin D deficiency or toxicity, and is often ordered when someone has symptoms of a vitamin D deficiency, like bone weakness, softness, or fractures.

Who should get a Vitamin D 25-Hydroxy Total test?

Individuals who are at risk of vitamin D deficiency, such as those with limited sunlight exposure, those with dark skin, older adults, individuals with fat malabsorption conditions, and those who have undergone gastric bypass surgery, should consider this test. Additionally, the test might be recommended for individuals with osteoporosis or other bone disorders.

Relation to Health Conditions

How can the Vitamin D 25-Hydroxy Total test help in diagnosing bone disorders?

Vitamin D is essential for bone health as it helps in calcium absorption. Low levels of vitamin D can lead to softening of bones (osteomalacia) in adults and rickets in children. A Vitamin D 25-Hydroxy Total test can aid in diagnosing these conditions by indicating whether levels of the vitamin are insufficient.

Can a Vitamin D 25-Hydroxy Total test help in managing autoimmune diseases?

Vitamin D plays a role in immune function, and studies have shown a relationship between low vitamin D levels and certain autoimmune diseases like multiple sclerosis and rheumatoid arthritis. Doctors may use the Vitamin D 25-Hydroxy Total test to assess vitamin D status in patients with these conditions.

What is the relationship between vitamin D levels and cardiovascular disease?

Several studies suggest that low levels of vitamin D might be associated with an increased risk of cardiovascular disease, including hypertension, heart failure, and ischemic heart disease. Therefore, the Vitamin D 25-Hydroxy Total test may be used in evaluating cardiovascular risk.

Can the Vitamin D 25-Hydroxy Total test be used to monitor kidney disease?

Yes, vitamin D levels are often monitored in individuals with kidney disease. The kidneys convert vitamin D into its active form, and kidney disease can therefore lead to low levels of active vitamin D.

How does the Vitamin D 25-Hydroxy Total test relate to certain cancers?

Research suggests that low vitamin D levels may be associated with an increased risk of certain cancers, including breast, prostate, and colon cancer. However, more research is needed to understand this link fully.

Preparation and Frequency of Testing

Is fasting required before a Vitamin D 25-Hydroxy Total test?

Fasting is preferred, but is not required before a Vitamin D 25-Hydroxy Total test.

How often should I have a Vitamin D 25-Hydroxy Total test?

The frequency of testing depends on your individual health status and risk factors. Your healthcare provider will recommend how often you should have this test based on your specific circumstances.

Interpretation of Results

What is considered a healthy level of vitamin D in the Vitamin D 25-Hydroxy Total test?

Generally, a level of 30 to 100 ng/mL is considered adequate for healthy people. A level less than 12.0 ng/mL indicates vitamin D deficiency.

What do low levels in the Vitamin D 25-Hydroxy Total test indicate?

Low levels of Vitamin D may indicate that you are not getting enough exposure to sunlight, are not eating enough vitamin D-rich foods, or that your body is not absorbing vitamin D properly. Low levels can lead to bone problems such as rickets in children or osteomalacia in adults.

What do high levels in the Vitamin D 25-Hydroxy Total test indicate?

High levels of Vitamin D can indicate a condition called hypervitaminosis D, or vitamin D toxicity. This usually happens from overconsumption of vitamin D supplements, not from diet or sun exposure.

How should I interpret the results of the Vitamin D 25-Hydroxy Total test in relation to my overall health?

Vitamin D is essential for bone health and plays a role in immune function. Your healthcare provider will help you interpret your results in the context of your overall health, other test results, and your personal health history.

Can the Vitamin D 25-Hydroxy Total test replace a healthy lifestyle in maintaining optimal vitamin D levels?

No, a Vitamin D 25-Hydroxy Total test can't replace a healthy lifestyle. Adequate sun exposure, a diet rich in vitamin D or fortified with vitamin D, and regular exercise are still important for maintaining optimal vitamin D levels and overall health.

What if my Vitamin D 25-Hydroxy Total test levels are not improving despite supplementation?

If your levels aren't improving despite supplementation, you may not be absorbing the vitamin D properly, or you may not be taking a sufficient dose. Your healthcare provider can help you figure out the cause and adjust your treatment plan accordingly.

How is the Vitamin D 25-Hydroxy Total test different from the Vitamin D 1,25-Dihydroxy test?

The Vitamin D 25-Hydroxy Total test measures the inactive form of vitamin D, and is the most accurate measure of your overall vitamin D status. The Vitamin D 1,25-Dihydroxy test measures the active form of vitamin D, but is not usually used to determine vitamin D status because it has a short half-life and levels can change rapidly in response to calcium intake.

Are there medications that can affect my Vitamin D 25-Hydroxy Total test results?

Yes, certain medications can affect your vitamin D levels and your test results. These include certain antifungal medications, anticonvulsants, glucocorticoids, HIV/AIDS medicines, and the weight-loss drug orlistat (brand names include Alli and Xenical). If you are taking any of these, tell your healthcare provider.

Is Vitamin D 25-Hydroxy Total test accurate for people of all ages?

Yes, the Vitamin D 25-Hydroxy Total test is accurate for people of all ages. However, older adults are at greater risk of vitamin D deficiency because their skin doesn't convert sunlight into vitamin D as efficiently, they may get less outdoor exposure, and they may not get adequate vitamin D in their diet.

Can Vitamin D 25-Hydroxy Total test be used to monitor the effectiveness of treatment in patients with vitamin D deficiency?

Yes, the Vitamin D 25-Hydroxy Total test is used to monitor levels of vitamin D before and after treatment to determine the effectiveness of the treatment.

What happens if vitamin D deficiency is left untreated?

If left untreated, vitamin D deficiency can leadto a number of health problems. Children can develop rickets, a disease that causes bone weakness and deformities. Adults can develop osteomalacia, a condition that causes bone pain and muscle weakness. Severe and long-term deficiency can also lead to osteoporosis, a condition that weakens bones and makes them prone to fractures.

Can vitamin D toxicity occur from excessive sun exposure?

No, your body regulates the amount of vitamin D produced from sunlight, and even with excessive exposure, it won't create too much vitamin D. Vitamin D toxicity generally occurs from overconsumption of vitamin D supplements.

Can I take over-the-counter vitamin D supplements without a doctor's prescription?

While you can take over-the-counter vitamin D supplements without a prescription, it's best to talk to your healthcare provider first, especially if you're planning to take a high dose. Too much vitamin D can be harmful.

Can diseases other than bone disorders also cause vitamin D deficiency?

Yes, other than bone disorders, diseases such as Crohn's disease, celiac disease, and kidney disease can also affect the body's ability to absorb or convert vitamin D, leading to deficiency.

Can a Vitamin D 25-Hydroxy Total test be used in diagnosing mental health conditions?

While the Vitamin D 25-Hydroxy Total test itself cannot diagnose mental health conditions, research has shown a correlation between low levels of vitamin D and mood disorders such as depression and anxiety. More research is needed, however, to fully understand this relationship. It's important to have a holistic approach when diagnosing and treating mental health conditions, and a healthcare provider may consider a Vitamin D 25-Hydroxy Total test as part of a broader diagnostic process.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.