It can be a symptom of certain types of diabetes but if you are worried and you havnt made any dietary changes to warrant the weight loss I would get to the Dr asap as it could be something way worse than diabetes.
If you are constantly thirsty amd constantly having to go to the toilet, then it could be symtoms of Diabetes.
But as said above, first port of call must be your GP if you are losing weight without trying, as it could be any number of things and needs to be diagnosed ASAP.