Vitamin D Test: Purpose, Risks, and Results

Nov 07, 2024

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A vitamin D test is a blood test that measures the level of vitamin D (calciferol) in your blood. It can indicate whether the vitamin D levels in your body are low or high.

Low vitamin D levels can weaken bones and increase the risks of falls and fractures. High vitamin D levels are rare but can cause serious symptoms such as muscle weakness, kidney stones, or irregular heartbeat.

Your healthcare provider may recommend the vitamin D test if you're experiencing signs of low vitamin D levels, such as bone pain, muscle weakness, or low bone density, or if you are at risk for developing vitamin D deficiency.

The vitamin D test helps detect whether vitamin D levels in your blood are high or low. Vitamin D helps absorb calcium, which is essential for developing strong bones. Vitamin D also helps your muscles, nerves, and immune system function properly.

Before the body can use vitamin D, the liver needs to turn the nutrient into a form of vitamin D called 25-hydroxyvitamin D, or 25(OH)D. The vitamin D test usually measures the level of 25(OH)D in your blood.

Your healthcare provider may recommend the test if you have signs of low vitamin D levels, such as:

Providers may also recommend the test if you have a higher risk of developing vitamin D deficiency, even if you're asymptomatic. You could be at a higher risk if you:

Low vitamin D levels can also affect newborns and children. Children with darker skin tones who live in areas with less sun exposure and children with diets low in vitamin D may be at a higher risk for vitamin D deficiency. Healthcare providers may recommend the test for nursing newborns since breastmilk is low in vitamin D.

The vitamin D test does not require any special preparation. If you are getting any other blood tests done at the same time, those might require preparation, such as fasting. Talk to your healthcare provider to make sure.

A vitamin D test generally occurs at a healthcare provider's office or a diagnostic clinic. Here are a few tips to keep in mind before going for the test:

The vitamin D test involves drawing blood from a vein in your arm. You may feel a slight sting when the needle goes in or out, but the procedure usually takes less than five minutes.

During a vitamin D test, your healthcare provider or a phlebotomist (a medical professional trained in drawing blood) takes blood from a vein in your arm. You can sit comfortably in a chair or lie down for the test. The provider will do the following steps when drawing blood for your vitamin D test:

In the case of newborns or children, healthcare providers will use a sharp tool called a lancet to puncture the skin and draw blood. The blood is collected on a slide or test strip, and a bandage is placed over the area to prevent further bleeding.

After your appointment, you should be able to go home and resume your daily activities. If you experience dizziness, extreme sweating, or nausea, your healthcare provider may ask you to stay at the office until you fully recover.

If your results show that routine vitamin D tests are medically necessary, you should have them every 3-6 months. Retesting ensures you receive proper treatment and lowers the chance of vitamin D toxicity from overtreatment.

Like most blood tests, the vitamin D test is generally safe with no significant risks. You may feel slight pain or bruising at the needle site after the test, but these symptoms should disappear quickly.

In rare cases, people can experience serious complications from a blood test, including:

Vitamin D test results, similar to other blood tests, should be available within a few days or weeks after your test. Contact your healthcare provider if you haven't received your test results after a couple of weeks.

Your vitamin D results may include your overall vitamin D level or separate results for vitamin D2 and D3. These two types of vitamin D work similarly in the body, and their sum in your test results is your total vitamin D level. The total vitamin D level is the most important number and what your healthcare provider will use to give you a diagnosis.

Your vitamin D test results will show whether your levels are low, normal, or high. The level ranges can vary slightly depending on the lab used to analyze the test.

Low vitamin D levels of less than 12 nanograms per milliliter may indicate a vitamin D deficiency. Levels between 12-20 nanograms per milliliter are considered inadequate, meaning you aren't deficient, but your bones and overall health may be affected. If you have low vitamin D levels, it could be due to:

Vitamin D deficiency can also increase the risk of certain severe conditions such as cancer, cardiovascular disease, diabetes, depression, and autoimmune diseases.

Normal vitamin D levels can range between 20 and 50 nanograms per milliliter, which is ideal for bone and overall health.

Although rare, high levels of vitamin D can occur when you take too much vitamin D. High vitamin D levels are over 50 nanograms per milliliter, and very high levels are 150 nanograms per milliliter.

Very high levels of vitamin D in your blood can cause:

In some cases, excessively high levels of vitamin D may cause calcium buildup in soft tissues, kidney failure, irregular heartbeat, and even death.

The vitamin D test helps determine the vitamin D level in your blood. Your healthcare provider may recommend the test if you have symptoms of low or high vitamin D levels.

Vitamin D tests are quick, safe, and have minimal risks, such as soreness or bruising in the area where blood was drawn. Most people can resume normal activities immediately after the test, and test results are typically available within a few days.

Reach out to your healthcare provider if you have concerns about your vitamin D intake, experience symptoms, or have questions about the test or your results.

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