Elevated Free T3 generally indicates hyperthyroidism and thyrotoxicosis (a condition where there is an excessive amount of thyroid hormone in the blood), resulting from an overactive thyroid gland. Common causes of this condition include Graves' disease, thyroid nodules, thyroiditis (inflammation of the thyroid gland), and goiter; rarely, thyroid cancer can also lead to elevated Free T3.

High Free T3 levels can cause various symptoms in the body. If you are experiencing one or more of the following symptoms:
* Unexplained weight loss
* Increased bowel movements
* Irregular heartbeat (arrhythmia)
* Tremors
* Diarrhea
* Frequent urination
* Bone loss
* Feeling tense and angry

It is advisable to consult a healthcare professional. After a diagnosis of hyperthyroidism by a doctor, Free T3 tests can help determine the severity of the condition. The higher the Free T3 level, the more severe the hyperthyroidism may be.