The common side effects of fulvic acid supplements are not known due to a lack of reliable medical research, notes WebMD. However, fulvic acid is not recommended for those who suffer from an autoimmune disorder as it is believed that the supplement may cause the immune system to become overactive.
Fulvic acid supplements are often used to enhance immune system function and to treat or prevent the occurrence of viral infections such as influenza, notes WebMD. However, there is no medical evidence supporting the efficacy of fulvic acid supplements as either a preventive or curative measure. Laboratory and research studies have also shown a correlation between fulvic acid use and the onset of circulatory disease, thyroid disorders and joint disease, reports MedicineNet.
Owing to the lack of research into fulvic acid supplements, there is no medically approved dosing guide for fulvic acid use. Women who are pregnant or nursing are advised not to use fulvic acid supplements as their effect on fetal and infant health is unknown, reports WebMD.
Fulvic acid is a form of humic acid, an organic compound commonly used as a soil enhancement, according to Wikipedia. Fulvic acid contains more oxygen than the humic acids used in agricultural contexts and is more readily absorbed by the human body.