It might not be the particular vitamin that you are taking, as far as the brand.
I cannot take "adult" strength vitamins, or prenatal vitamins when I was pregnant any of the three times I was expecting. The strength of them made/makes me nauseated and sometimes I vomited after taking them.
The solution that worked for me:
~Take half a vitamin during one meal, and the other half at the next meal.
~Do what I do now, which is take a children's chewable vitamin. If you are eating a decent diet, then you obviously get some of your nutrients through food-so taking a children's vitamin adds enough to fill in any areas where you might be lacking.
Start weight after baby #3: 233.9
Current weight: 143
90 pounds lost!