Do you urinate frequently when you are losing weight?

No. Compound that helps you urinate more is beta-tcp and detox meds but the effect goes away after initial detox - consistent urination could be due to sugar in urine make sure you are not drinking high sugar drinks or have diabetes.
Drinking more water? Urinating more is normal only if one is drinking more water, green tea, etc... Drinking water can help with weight loss if it is substituting for other drinks that contain calories. Drinking water before each meal can also fill up the stomach somewhat, and make a person satisfied with a smaller meal. If one is not drinking more, but seems to keep on urinating, a doctor's evaluation should be done.