On Monday we ate having some INSET in which we will hear about how drinking water improves concentration etc. I am very dubious. Apart from anything else, blood concentration is closely monitored and controlled by ADH and other hormones. So drinking water will have, at best, a temporary effect on blood concentration. However, just how quickly does this hormone control operate? If I were to drink a glass of water now, for how long would my blood be diluted? Are we talking about seconds or minutes or hours? Can anyone steer me in the right direction? Just for the record, my best guess is that blood concentration would be back to normal within a couple of minutes. But I'd like to be able to prove this.