It can cause an initial drop in energy and feeling 'sickly' due to the die-off of pathogens it killed. It is especially damaging to cancerous cells. Ozone activates both monocytes and lymphocytes. It increases the oxygen supply to the brain. The first impression gotten is that it makes the water taste awful just like hydrogen peroxide makes it taste.
Second impression is that it is somewhat harsh on the stomach because it is such a strong oxidizer.
Of course, I'm just geussing how long to ozonate the water because the only recommendations are for just treating water to make it healthier to drink which is 5-10 minutes per gallon. I've started at 15 minutes with 2 cups water and have been drinking 1 cup every morning. I'd rather experience what's 'too much' instead of my customers. I think that if someone didn't have an intestinal infection that they might only feel more energy from taking it. The unit I bought is the cheapest I could find but it does its job well.