A physical examination is performed by your vet. In most cases, a tumors can be felt on the thyroid glands.
A blood test is taken to check T3 and T4 levels. Over 90% of cats with hyperthyroidism show elevated hormone levels. Normal T4 levels in cats range from 12.87 nmol/L – 38.61 nmol/L.
A technetium scan can be done at specialized veterinary practices. A contrast agent is injected allowing the functioning part of thyroid glands to easily be seen.
If results are inconclusive, advanced imaging can be used. An example is thyroid scintigraphy, which provides a visual look at function and structure of the thyroid glands.