[James_Henry]

The safest way is to take an occasional test for your vitamin d levels. There are tests that you can take at home that aren't too expensive!

[secabeen]

Yep. I work inside a lot, so I started taking 5000IU of D a day. After two weeks, I had my levels tested and it showed a level of 37. When fall comes around, and I'm outside even less, I'll probably up the dosage for a week or two, then test again. Target is between 50 and 70, so I definitely need more.

[BurningFrog]

Thanks. I didn't know.

Amazon has a few options in the $50-90 range.

You prick your finger, draw a "small amount" of blood, and send it to a lab.

[secabeen]

The order it yourself lab companies compete on the Vitamin D test, you can usually get one for $40.