I don't have a thyroid due to cancer, my doc is currently trying to get me on the right thyroid med dosage. Could excessive thirst be a symptom?

Possibly, but. Getting to the right dose of thyroid supplement is important and may take months; a combination of thyroid function test and clinical examination by an internist or endocrinologist will easily be able to do this. There pages of symptoms that could be part of under or over active thyroid function, since it affects almost all organ systems. So it may or may not be the cause of thirst. Check c doc.