Can i take multivitamins, fiber supplements, fish oil, and biotin vitamins at the same time?

Probably: Unlikely a problem, but why do you wish to take all of these items? I know it is popular to take vitamins, herbals, high fibers, but in most cases, this is un-necessary and costly. Might see a nutritionist or a physician who focuses on alternative medicine, and see what they might think.

Yes, But Why?: It is generally safe to take these vitamins and supplements, or they would have been taken off the market. However, they are almost always totally useless unless you have a specific vitamin deficiency, and can be a danger. Despite the sales propaganda, we are not mostly vitamin deficient as long as we have a reasonable diet. Save your money and buy a gym membership for the most benefit.