Is it possible to consume too much of a certain nutritional supplement? Generally, most nutritional supplements can be taken in much higher doses than the "recommended doses" without any risks whatsoever. Nevertheless, a few nutritional supplements, mostly fat-soluble ones and some minerals, should not be taken in larger doses than prescribed. For instance, very large amounts of vitamins A and D can have harmful side effects, especially for pregnant women. Before starting on nutritional supplements, it is important that you seek advice from a medical professional experienced in nutritional medicine.