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.
Selenium is LIKELY SAFE for most people when taken by mouth in doses less than 400 mcg daily, short-term. Selenium is POSSIBLY UNSAFE when taken by mouth in high doses or for long-term. Taking doses above 400 mcg can increase the risk of developing selenium toxicity.