Rapid weight gain over the last couple weeks. how do you tell if it's fluid ?

Go see your doc...: Rapid weight gain is best assessed by your doctor who could determine if this is because of retained fluid due to an endocrine (thyroid/adrenal glands), kidney or cardiac problem, or simply because of increased calories.Your doc would ask pertinent questions and perform a physical examination. Shortness of breath, swelling of your legs, feet, abdomen or around the eyes may suggest fluid retention.