A High Medication Dose or Quantity of Anything, Suddenly Applied, is Seldom a Good Thing.
Think of your body as a system that is stable. Maybe not the way you want it to be, but stable none the less.
For example, a working aquarium is normally placid, with no ripples or waves, and the fish are calm and unconcerned. Now, gently push on one side, just a little bit (normal or low dose). What will happen? A few ripples, the fish will barely notice, if they notice at all.
After the ripples have settled down and the aquarium is still again, rock the aquarium back and forth vigorously (high dose). You will get waves, the fish will slosh around, some might even fall out.
A gentle push did not upset the aquarium, but a large push did upset the aquarium in a big way. And it will take awhile for that system to stabilize. The waves will get smaller and smaller, and you may have to rescue some fish!
In the engineering world this is called an impulse function. This is what you're doing to your body when you take a large medication dosage.
Take me as a real life example.
In my case it was EPO. My hemoglobin dropped too low, it was about 8, so I was prescribed a large weekly dose of 20,000 units, which caused all sorts of side effects (the large push). Then, at our request the weekly dose was reduced to 15,000 units and split over 3 days each week. The side effects either disappeared or were greatly diminished.
Moral of the story, if you have to add something to your body, do it slowly.