If i had rai uptake scan done 6 months ago, should i have another one done if my symptoms still persist?

No: Unnecessary unless your physician feels it would be helpful.

Depends: Usually radioiodine uptake and scan are performed for hyperthyroidism or hypothyroidism. Medications are usually prescribed for these diseaes. Radioiodine therapy is sometimes used for hyperthyroidism. Unless your physician feels because of therapy issues or change in symptoms, the test is not usually repeated on regular basis. If following thyroid cancer, that scan is done for surveillance.