3.Get your vitamin D blood levels checked! The only way to determine the correct dose is to have your blood tested since there are so many variables that influence your vitamin D status. I recommend using Lab Corp in the U.S. Getting the correct test is the first step in this process, as there are TWO vitamin D tests currently being offered: 1,25(OH)D and 25(OH)D.
From my perspective, the preferred test your doctor needs to order is 25(OH)D, also called 25-hydroxyvitamin D, which is the better marker of overall D status. This is the marker that is most strongly associated with overall health. You'll want to optimize your levels according to the chart below. If you currently have Parkinson's disease you will want to keep your vitamin D level in the higher 70-100 ng/ml range to help fight the disease.