Reply To: Hi. I have been taking 10,000 IU for about a year and my Serum D level reached 130.54mg/nl. After stopping the supplement for 4 weeks, the level dropped to 73 mg/nl. Should I start taking the D tablets again and try to maintain that sort of level and if so how much? Has anyone been harmed by taking too much Vit D and what would too much be? Thanks for any advice.