This dataset provides the data collected for a trial investigating the role of hydration status on glycaemic regulation in healthy adults (n = 16; n = 8 male). To our knowledge, the effect of hydration status on glycemia has never been causally investigated in healthy adults. Therefore, the goal was to explore how acute hypohydration impacts blood sugar control in healthy adults. The trial was a randomised crossover trial, with each trial arm lasting 5 days. The first 3 days were lifestyle monitoring, day 4 was a dehydration/rehydration day (including lifestyle monitoring), and day 5 was the full trial day. The trial arms were hypohydrated (HYPO), or rehydrated (RE).