Test Overview

A vitamin D test measures the amount of vitamin D in the blood. The vitamin D test is also called the 25-hydroxy vitamin D, or 25(OH)D, test.

Your body needs vitamin D to absorb calcium. Calcium keeps your bones and muscles healthy and strong. If your muscles don't get enough calcium, they can cramp, hurt, or feel weak. You may have long-term (chronic) muscle aches and pains. If you don't get enough vitamin D throughout life, you are more likely to have thin and brittle bones (osteoporosis) in your later years.

Children who don't get enough vitamin D may not grow as much as others their age. They also have a chance of getting a rare disease called rickets.

Your body uses sunshine to make its own vitamin D. Vitamin D is found in foods such as egg yolks, liver, and saltwater fish. It is added to some food products, such as milk and fortified soy or other plant-based beverages. You can also get it as supplements, often combined with calcium. Osteoporosis Canada recommends that Canadian adults take daily vitamin D supplements. ^{footnote 1}

The vitamin D test is usually done in a doctor's office or a lab. Or you may be able to buy an at-home version of the test. Discuss the benefits and risks of at-home testing with your doctor before you buy one of these tests.