I agree with mammo, its best to seek your doctors advice
I would check with your doctors on this. Diabetes and blood pressure can both cause one to be light headed. If you are light headed after being in the hot tub, then I would think it's impacting you in a bad way. But your sugar and BP could also be dropping too low, I guess what I'm saying is it depends on "when" you are lightheaded.
I hear that hot tubs can be dangerous, however, at this moment I am lightheaded and it is anxiety, I hope.