Can dehydration cause your efgr to go down 9.1 points.. I know it can cause it to decrease and creatine to increase but isn't 9.1 points a lot ?

Can dehydration cause your efgr to go down 9.1 points.. I recently had efgr of 43.5 in Feb., but May's lab results for efgr was 34.4 how many points can dehydration cause an efgr to go down
I know dehydration can cause a decrease but specifically how many points can it cause it to decrease?