Under-Active Thyroid Test to measure the TSH level in your blood to identify an underactive thyroid. The test kit is not able to identify an overactive thyroid. 
The symptoms of an underactive thyroid are often vague and usually develop quite slowly such that you may not notice them. When the body doesn’t have enough thyroid hormone many of the body’s functions slow down. 

You should think about underactive thyroid with the following symptoms: 

Tiredness 
Weight gain 
Low mood 
Being sensitive to the cold 
Dry skin and dry hair 
Muscle aches, weakness and cramps 
Constipation 
Loss of libido (sex drive) 
Irregular period or heavy periods 
Carpal tunnel syndrome