But too much of supplements, including fish oil and vitamin D, can be harmful. A toxicologist shared the side effects of overdoing some of the most popular supplements. AdvertisementChilcott shared the long-term risks of taking too much of some of the most popular supplements. You're unlikely to get symptoms from taking too much vitamin D if you're taking less than 250 mcg a day, according to the ODS. Of all the supplements Chilcott spoke about, he said this was the one that's the most potentially risky, but only at very high doses.

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Persons: —, Rob Chilcott, Chilcott, it's Organizations: Service, University of Hertfordshire, FDA, Cleveland Clinic, BI, US Food and Drug Administration