Does this test have other names?
25-hydroxyvitamin D (25-high-DROX-ee-VIE-tuh-min D), 25(OH)D
What is this test?
Vitamin D is mainly found in fortified dairy foods, juice, breakfast cereal, and certain
fish. This vitamin plays many roles in the body. But because it helps the body absorb
calcium from foods and supplements, it's particularly important for bone health. Vitamin
D has many additional roles in the body.
Vitamin D comes in several forms. When ultraviolet light, such as sunlight, hits your
skin, it creates vitamin D3. D2 is used to fortify dairy foods. Both of these are
further processed by your liver and kidneys into a form your body can use. Most tests
for vitamin D check the level of a form circulating in the body called 25-hydroxyvitamin
D, also called 25(OH)D.
Why do I need this test?
Vitamin D testing has become much more popular in recent years. Your healthcare provider
may check your vitamin D levels to find out if you have any risks to bone health.
These might be:
You may also need this test if you are at risk for low vitamin D levels. Risks include:
Being an older adult
Having difficulty absorbing fat from your diet
Having chronic kidney disease
Have dark skin pigmentation
Being a breastfed baby
Vitamin D has many effects in the body. You may need this test to help your provider
diagnose or treat:
What other tests might I have along with this test?
A healthcare provider may also want to check your parathyroid hormone levels and your
What do my test results mean?
A result for a lab test may be affected by many things, including the method the laboratory
uses to do the test. If your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
Children and adults need more than 30 nanograms per milliliter (ng/ml) of vitamin
D. The optimal level of 25(OH)D is usually between 30 and 60 ng/mL. Recommended daily
amounts range from 400 to 800 international units (IU) per day based on your age.
Levels lower than normal can mean you are:
Not making enough vitamin D on your own
Not getting enough vitamin D in your diet
Not absorbing vitamin D from your food as you should
Lower levels may also mean that your body is not converting the vitamin as it should.
This might be because of kidney or liver disease.
Above-normal levels may be a sign that you're taking too much in supplement form.
How is this test done?
The test requires a blood sample, which is drawn through a needle from a vein in your
Does this test pose any risks?
Taking a blood sample with a needle carries risks that include bleeding, infection,
bruising, and a sense of lightheadedness. When the needle pricks your arm, you may
feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.
What might affect my test results?
The amount of time you spend in the sunlight, your diet, and whether you take vitamin
D in supplement form can affect your vitamin D levels. Ask your healthcare provider
if any health conditions you have or medicines you take could affect your results.
How do I get ready for this test?
Tell your healthcare provider if you take vitamin D supplements. Also be sure your provider knows
about all medicines, herbs, vitamins, and supplements you are taking. This includes
medicines that don't need a prescription and any illicit drugs you may use.