My doc says i should not worry about my vit d level (18) & that taking it in pill form is useless bc the body can only use it from the sun. true?

Not clear.: Data on vit d is not compelling. Supplementation at your age regardless of level is not likely to prevent any fracture. Recent us preventive services task force guidelines on this clearly note that 2000 iu/day is upper limit of safe. If i were you i would drop the dose down to 2000 iu/day max and stop measuring levels. Review the literature in 10 years when we have a better answer.