I am probably the woman in the world ingested most borax, :)) yes and I am very approx with this too. It is like salt, if too much, you get thirsty, drink water.
That said, sometimes we have to choose, to have therapeutic effect may cause some symptoms / adverse reactions / detox for a while. Been there, but it was always adjustable.
I am not the right to adress with accurate measures, as I spice for the day so to speak, higly governed by intuition, whats good for me or not; my body is wiser than my brain. It has worked well, so far.