ZRT will perform the 25(OH)D test in their lab and send the results directly back to you. The Vitamin D Council has verified that results obtained by ZRT are accurate and correspond very well to the results given by both LabCorp and DiaSorin RIA. These tests are good for either adults or children and avoid the venipuncture many children dislike.
However, if you have insurance, you may be able to save money by going to your doctor instead. You can have your doctor order the test—some insurance companies will pay for a 25(OH)D test, some will not. Unfortunately, about 20% of United States doctors order the wrong test. They order a 1,25-dihydroxy-vitamin D, thinking that by measuring the most potent steroid in the human body, calcitriol, they are getting useful information. They are not. 1,25-dihydroxy-vitamin D is an adaptive hormone; it goes up and down with calcium intake. So these doctors see the 1,25-dihydroxy-vitamin D is normal or high and tell their patients that they are ok when really, they are vitamin D deficient—advice that may prove fatal. Furthermore, most doctors who see a 25(OH)D of 30 ng/ml will tell you that level is fine when it is not—that is, few doctors know how to correctly interpret the test results. With ZRT, you are in control of when you test, how often you test, and what you do with the results.