I've been taking 5000IU/day which is above the wikipedia recommended dose of 4000. I was prescribed 50000 pills for a week, but it can cause kidney damage at higher doses I read on wikipedia.
I just can't find anything to stop my wheezing or help my sleep apnea... I also don't get a lot of natural sunlight
Vitamin D is becoming more well understood now. It used to be that experts thought you needed only a small amount; newer research is changing this belief. However, Vitamin D is fat soluble, not water soluble, which means it can accumulate in the body and cause overdose. It seems like 2000 IU is generally considered safe for most people in northern climates. Personally, I wouldn't feel comfortable going a lot higher than that on a regular basis without the direction of a doctor and my levels being monitored. It's a little more complicated than straight "vitamins" because it acts like a hormone in the body.