It's fat-soluble so you're not as likely to just piss it out like the usual vitamins. D3 gets pretty good absorption. I wouldn't take it as a dry pill, if they even manufacture it like that. Get it in a liquid gel format that has it suspended in lipids. Take it with a meal or after.
If you really want to be anal about it, best move is to get your levels tested and then start supplementing and test levels again after a month, then up or down your dosage accordingly till you know how much you need to be taking daily. Most people depending on ethnicity, lifestyle/occupation, and locale just take like 500 - 5,000 IU D3 daily. If you're a white dude who goes surfing every day on the equator, you're probably good. If you're a black dude with a desk job, there's about a 90% chance you're deficient.
A doctor can diagnose extreme deficiency and might put you on like 50,000+ IU / week for a short while.
