When is thyroid function test recommended for hypothyroidism?

The test checks thyroid-related hormone levels in a blood sample. Results help a clinician decide whether the thyroid is producing too little hormone, whether replacement is having the intended effect, or whether another explanation for symptoms should be considered. Tiredness, feeling cold, constipation, dry skin and changes in weight can have several causes, so symptoms alone do not establish hypothyroidism.

Arrange an assessment if you have persistent symptoms or a thyroid-related risk factor, such as a previous thyroid problem, neck surgery or medicines that can affect thyroid activity. Tell the clinician about pregnancy, plans for pregnancy, supplements and all medicines. If you take thyroid replacement, use it as prescribed and follow the timing instructions given for the blood test. Keep follow-up appointments so results can be interpreted alongside your symptoms and dose.

Seek urgent medical help for severe breathlessness, chest pain, fainting, marked confusion or extreme drowsiness. Contact your clinician promptly if symptoms worsen after starting or changing thyroid medicine, or if you develop a racing heartbeat, shaking or unusual agitation. Pregnancy or plans to become pregnant also warrant early review because thyroid monitoring may need closer attention.

Ask which thyroid tests are needed, when results should be reviewed, whether any medicine or supplement can affect the result, and what symptoms should prompt an earlier appointment.