The best way to establish your vitamin D levels is to take a blood test . There are several forms of vitamin D , and popular opinion suggests that the best test to take is the 25(OH) D blood test , which stands for 25-hydroxyvitamin D . 1 You can take th is test either at your doctor ’ s or purchase a n in-home testing kit 2 . Both ways produce accurate results. The test involves taking a small sample of your blood via a tiny prick on the finger, which is then analyzed in a laboratory to determine vitamin D levels. Testing for vitamin D levels 3 has become more common and easy to do. For a time, the perception was that it was an expensive test that provided little or no definite proof for treatment. However, research 4 has shown that early testing can help with deficiency diagnosis and treatment. Fortunately , testing for vitamin D levels has become more prevalent these days with an increasing number of practitioners regul