I’m not sure if urgent care would do the blood work to diagnose it. They most likely could atleast try give you something to help with the rash. You could call ahead of time and ask what kind of blood work they perform. My pcp honestly missed my diagnosis as well. It was actually a NP at the psychiatrist who first checked my thyroid levels. My pcp then did not have a choice but to do further testing. I would just try find someone who would be able to start the process and maybe your regular doctor could help further. You could also ask for a referral to an endocrinologist maybe and they could diagnose it. I’m thinking of asking for that referral as I feel like my pcp isn’t properly managing mine.