I had the same problem until I researched it. Now I don't have that problem anymore. Vitamin D has to be taken with a full meal, something with some FAT in it because it is a fat soluble vitamin.  Never take Vitamin D on an empty stomach.  Doctors prescribe Vitamin D, but they don't tell you that you need to take calcium, and especially MAGNESIUM, along with it. Otherwise your electrolytes get out of balance and you have the heart palps. A balanced meal should contain enough vegetables and protein to provide the magnesium and calcium the Vitamin D requires. If taking it with a full meal does not work, take it with a meal AND take a magnesium- calcium supplement along with it.  This is especially important if you don't eat a balanced diet. Just check with your doc to make sure it's ok for you to take a supplement in case you have any medications or medical conditions that would not mesh with the supplements. Remember that all vitamins work together and not independently of each other.  Vitamin D also needs a little Vitamin A to be effective as well.  So I always drink a small shot of carrot juice each day along with my meal  in which I'm taking the Vitamin D. This worked for me; I feel great and do feel the full benefits of the Vitamin D now...the extra care and effort are truly worth it... good luck!