Final answer:
When encountering low TSH and high free T3/T4 levels, further testing is needed to confirm the diagnosis and determine the appropriate treatment plan.
Step-by-step explanation:
The best step when encountering a low Thyroid Stimulating Hormone (TSH) level and high free T3 and T4 levels is to evaluate the overall clinical context and other accompanying symptoms. These blood test results indicate a possible hyperthyroidism, where the thyroid gland is overactive. The next best step would be to confirm the diagnosis by performing additional tests, such as thyroid antibody testing or nuclear thyroid scan, to determine the underlying cause and decide on an appropriate treatment plan.