 [ Symptoms ] 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 is 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 could not 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 [ Disease ] this happened to me go to nose ear and throat doc may have fluid trapped in the inner ear