Your doctor can detect unusual thyroid hormone levels with a blood test. Regular screening is important if you have a higher risk of thyroid dysfunction, such as if you’re pregnant and have: symptoms of thyroid dysfunction a personal or family history of thyroid disease previous thyroid surgery goitre (swelling of the thyroid) Regular screening is also recommended if you: have a history of miscarriage or premature birth have a history of infertility have type 1 diabetes live with overweight or obesity are aged 30 or older If you fit into one or more of these categories, ask your doctor or midwife if your thyroid function should be checked.