I took this for 5 days, starting with only 1 drop the first 2 mornings, then 2 drops in water the next 2 days, and then 3 drops on the 5th day. I felt really yucky by the 5th day, not nauseous enough to vomit, but I had to force myself to eat. Once I realized it was the methylene blue, I stopped taking it. I still wasn't feeling great that whole day I didn't take it, but better than the previous day. The 2nd day after stopping, I finally felt good again. Hope others fair better than me with this, but I will stick to my intermittent fasting which I've been doing for 4 years, and taking NMN for genome protection and autophagy.