I also worked up to 15 drops once a day and have hardly had a symptom at all. No real nausea or diarrhea to speak of.
Then I took one day off (as I was out of town) and resumed my 15 drops last night and got really really nauseous. I thought I was going to vomit (I didn't). Still no diarrhea, and I slept the nausea off, but it was bad for awhile there.