Balancing chemical equations is a key chemistry skill. Use these step by step instructions to write and balance chemical equations. Balancing chemical equations is a key chemistry skill. Use these step by step instructions to write and balance chemical equations.
So, there are many signs and symptoms of Selenium Overdose- some occur very early and some occur much later. 1  Early Signs: Some of the early signs of Selenium Toxicity are endocrine hormone disturbances- particularly thyroid issues. Poor hair and nail growth are early signs that are probably the easiest to notice.
What Are the Side Effects of Taking Selenium? The upper limit of healthy selenium intake is 400 micrograms. Side effects of too much selenium include brittle hair and nails. However, you would have to consistently consume way more than the upper limit over a long period of time before any signs of toxicity start to show.