Selenium yeast tablet is a kind of medicine used for supplementing mineral selenium, which also has the effect of enhancing human immunity, preventing cancer and preventing atherosclerosis, so it is often used clinically for tumor patients who have low selenium as well as the adjuvant treatment of coronary heart disease and cardiovascular disease. However, selenium yeast tablets are different from yeast tablets and cannot be taken for a long time, if taken for too long or in excess, it may lead to chronic selenium toxicity, which may clinically cause damage to gastrointestinal function, liver and kidney function, as well as may also show adverse reactions such as deformation of nails and hair loss. Therefore, when taking selenium yeast tablets clinically, it is also necessary to closely monitor the selenium content of human body, and only when the selenium content of human body does not exceed the standard can be taken.