Whoever is suffering with chronic pain should check their Vitamin D level.. Check out the book "Power of Vitamin D" by Dr. Sarfraz Zaidi. He is MD, FACP, FACE is an Assistant Clinical Professor of Medicine at UCLA. Dr. Zaidi, a leading expert on Vitamin D, is also director of the Jamila Diabetes and Endocrine Medical Center in Thousand Oaks, California. The book has been an eye-opener for me. I suffer from skin rashes and have gone through various tests/biopsies with positive results. No dermatologist could diagnose the issue. But my PCP did a Vitamin D test, and found my level to be too low. I have been taking Vitamin D suplement for the past 3 months, and I see a great progress. Hope this helps you too..