Your Vitamin D levels are very low! Here at the Vitamin D Council we recommend 5000 iu a day for an adult. The Vitamin D Council also recommends a level of 50 ng/ml or above. That equals a level of 125 in nmol/l. There is no chance of toxicity taking 5000 iu a day! (It is safe to take 10,000 iu a day.) Take the Vitamin D daily for two or three months than test again to see what level you are at. You may need to take more than 5000 iu a day to reach the level of 50ng/ml (125 nmol/l) or above.
Please also read http://www.vitamindcouncil.org/about-vitamin-d/vitamin-d-and-other-vitamins-and-minerals/. Magnesium is very important along with some other Vitamins and minerals.