In 2016 my cbc mild anemia with hgb @ 11.9 and slightly low everything else, but rdw @ 15.1. now, 2019 and my cbc shows hgb @ 8.7, much lower everything else, but high rdw @ 17.1.. also my iron saturation is 4 w/ high tibc & uibc. is this dangerous?

Iron deficiency: This combination of lab results shows an iron deficiency anemia most likely from chronic blood loss. In your case blood loss from monthly periods is the most likely cause. I would also check your B12 and folic acid levels and stool sample for signs of occult blood, which will hopefully be ok. Your physician or a hematologist will treat you with appropriate iron supplements and get follow-up labs.