Is the absorption of vitamin D3 guaranteed when taken as a supplement? What brand of vitamin D3 is best in the market?

Vit D3 Well-Absorbed. Nothing is guaranteed. But I think you can feel comfortable that you are absorbing your Vitamin D3. I believe most brands are acceptable, but the best-tested brand is Bio-Tech. Bio-Tech D3 is the form that has been used in most of the major clinical studies. I recommend that D3 levels be maintained in the 60-70 ng/dl range. Usual dose to be in that range is 5-7,000 IU per day.
Malabsorption. If there are problems with nutrient absorption in the GI tracts, Vit D is sometimes not absorbed well. There are many causes, including GI surgery, inflammatory bowel disease, sprue, etc. In normal people, it is well absorbed.
Depends on the brand. Vitamin D3 is a fat-soluble vitamin, so remember to take it with food. I personally use USANA or GNC Vitamin D3. I see that you live in California, so make sure you get 15 minutes of sunlight every day so that your own body can produce Vitamin D.

Related Questions

What is the absorption time of vitamin D3 supplements?

Very slow. Vitamin d is really a hormone because it is made in skin from the action of sunlight, the main source of our vifamin d. It is absorbed poorly when taken in the form of d3 but is essential for most people in the northern or southern hemisphere because of our limited sun edposure and the use of sun screens when we are exposed to the sun. Read more...

While taking vitamin D (2000 I.U.) is it necessary to supplement the body with any additional vitamins for proper absorption and no calcification?

Yes, unless... I advise everyone taking Vit. D to also take Vit. K, which makes sure that the calcium absorbed by taking D winds up in your bones rather than arteries and soft tissues. Vitamin A also works synergistically with Vit D and K. If your diet is rich in Vit K (mostly dark leafy greens) you may not need to supplement. See http://tinyurl.com/4rqhnn4 Most adults need 5-8000 iu of D/day for optimal levels. Read more...

Can D2 and D3 be taken at the same time? Also, does Vitamin D affect the absorption of other vitamins and supplements?

I don't really know. why you would be taking both of them. Vitamin D2 is made by plants; vitamin D3 is made by human skin when exposed to sunlight.Foods may be fortified with either. I would pick one or the other (most supplement with D3) as they metabolize to the same form in the body. There is some affect of vitamin D on blood sugar as well as on liver metabolism/cytochrome P450 enzyme system.Review with pharmacist. Read more...