What your lab says is optimal is different then what we believe. Here at the VDC we believe in maintaining a “healthy” level of 50ng/ml. Please read http://www.vitamindcouncil.org/about-vitamin-d/vitamin-d-and-other-vitamins-and-minerals/. It is important. If there is enough calcium in your diet, then you do not need to supplement. Most diets are low in magnesium. If you take Vitamin D and get “symptoms”, it usually means a magnesium deficiency or another mineral or vitamin. You need to take 5000iu of Vitamin D3 a day to achieve the above level. If you weigh more than 150lbs, then you will have to take more. If you have any health issues, then you should tell me because the recommendation might be to take more than 5000iu. After 8 weeks of supplementing with Vitamin D, then you should try to get retested to make sure your levels have risen adequately. Never stop taking the Vitamin D because your levels will plummet again. If you have more questions, just ask.