Menu   WellSpan Health

Health Library

Health Library

Vitamin D

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. Often, health care providers check vitamin D levels to investigate threats to bone health, such as low calcium; osteomalacia, or soft bones caused by low vitamin D or problems using it; osteopenia; osteoporosis; and rickets in children.

Vitamin D has many effects in the body, and testing may be needed while diagnosing or treating:

  • People with risk factors for low vitamin D, such as those of older age, who have difficulty absorbing fat from the diet or have chronic kidney disease, or who are dark skin pigmentation breastfed babies

  • Problems with the parathyroid gland

  • Cancer

  • Autoimmune diseases such as multiple sclerosis and Crohn's disease

  • Psoriasis

  • Asthma

  • Weakness or falls  

What other tests might I have along with this test?

A health care provider may also want to check your parathyroid hormone levels and your calcium levels. 

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 health care provider.

Children and adults need more than 30 nanograms per milliliter (ng/ml) of vitamin D. The optimal level of 25(OH)D is usually said to be 30 to 60 ng/mL. Recommended daily amounts range from 400 to 800 international units (IU) per day based on age.

Levels lower than normal can indicate that you're not producing enough vitamin D on your own, you're not consuming enough in your diet, you're not absorbing it properly from your food, or your body is not converting it properly, perhaps 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 arm.

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.

How do I get ready for this test?

Tell the health care provider ordering your tests if you take vitamin D supplements, which could affect your results. Discuss whether any medical conditions you have or medications you're taking can affect your test results. 

Vitamin D - WellSpan Health

Author: Metcalf, Eric
Online Medical Reviewer: Hanrahan, John, MD
Online Medical Reviewer: Sohrabi, Farrokh, MD
Last Review Date: 2012-04-01T00:00:00
Published Date: 2012-07-27T00:00:00
Last Review Date: 2012-04-02T00:00:00
© 2015 WellSpan Health. All Rights Reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.

I would like to:

Are you sure you would like to cancel?

All information will be lost.

Yes No ×

About the provider search

This search will provide you with WellSpan Medical Group and Northern Lancaster County (Ephrata) Medical Group primary care physicians and specialists. If we don’t have a WellSpan Medical Group physician to meet your criteria, the search will expand to include community physicians who partner with WellSpan Medical Group physicians through the WellSpan Provider Network or provide care to patients on the Medical Staffs of WellSpan’s Hospitals.


Schedule Your Next Appointment Online with MyWellSpan

Use your MyWellSpan patient portal any time to view available appointments, and pick the date and time that best suits your schedule.

Go to MyWellSpan

New to this practice?

If you don't have a WellSpan primary care provider and would like to schedule a new patient appointment with a provider who is accepting patients, just log into your MyWellSpan account, and go to the Appointment Center section. As you progress through the scheduling process, you will be able to see the offices that are accepting new patients in relation to your zip code. If you are not enrolled in MyWellSpan, go to, call 1-866-638-1842 or speak with a member of the staff at a participating facility to sign up. New patient scheduling not available at all practices/programs.

Already a patient at this practice?

If you already have a relationship with a WellSpan practice, simply log into your account, and go to the Appointment Center section. As you progress through the scheduling process, you will be able to schedule an appointment with any provider or practice that already counts you as a patient. Online scheduling varies by practice/program.