there are a variety of factors that can cause vitamin d blood levels to drop. first off if he's getting less sunlight or using more sunscreen than usual that could decrease the amount he gets exposed to. also if he is eating less food and drink with vitamin d (like milk) that could decrease it. if he carries excess weight that can also decrease blood levels of vitamin d. remember that the recommended daily allowance for his age is 600iu. when levels are low doctors usually give higher than recommended amounts while monitoring blood levels. the key is to work with your doctor on the right level of supplementation that will keep his levels up. for more on vitamin d deficiency in sick kids see this webmd article.
my son is 3 years old and his level is 19. 3. he is now taking 800iu daily but what what could cause his levels to drop. my son's vitamin d level continues to drop and he is always getting sick. the dr recently increased his intake to 800 iu of vitamin d when his levels dropped to 19. 3. i took him back to the dr for further testing in an attempt ot find out why his levels were dropping but his dr couldn't figure it out. since his level has dropped from 24. 6 to19. 3 he has been sick twice. i know that his level was still too low but it had been going up then it dropped again.