You don't have to take 15 drops a day.
Its just a recommended amount to work up to.
If you get the D then you just back off a couple of drops and keep going.
The D just gives you your tolerance point at that time. Its an indicator and the body's way of eliminating the bad stuff when there's a lot to get rid of.
You would have been fine to continue at a lower amount.
I never got that. I just increased slowly.