How much can your weight be fluctuating without it considered to be gain or loss of weight?

Depends: This is an interesting Q. Not sure any published studies or evidences about a particular number. Normal Fluctuations of weights will depends on basal metabolism rate, balance between calorie intake & expenditure, & level of physical activity. Genetic predisposition also plays a role. In my practice, I advice my patient not to gain or loose >1 lbs weekly.