To confirm the diagnosis of hyperthyroidism your vet will take blood samples to measure the levels of thyroid hormone circulating in the bloodstream and to evaluate your cat's general condition and make sure it is not suffering from any other diseases.
In some cases, even although your vet strongly suspects that your cat is hyperthyroid, as the tests may not be conclusive.
This can be caused by a variety of factors:
→ Your cat may be at a very early stage of the disease
→ Thyroid hormone levels can fluctuate and can even be normal at some point in hyperthyroid cats.
→ Other diseases can influence thyroid hormone levels.
→ Your vet may need to repeat the blood tests after a week or so.
In some cases in might be necessary to carry out additional tests as well.
These tests could include
→ Special tests to evaluate thyroid gland function
→ Diagnostic imaging (e.g. nuclear scintigraphy, ultrasound) of the thyroid, particularly before radio-iodine therapy or corrective surgery is done.