Extreme hyperthyroidism: what you should know

[Hyperthyroidism](/conditions/hyperthyroidism/) means the thyroid releases more hormone than the body needs. Severe overactivity can cause a fast or irregular heartbeat, shaking, restlessness, heat intolerance, and weakness. Some people notice [Palpitations](/symptoms/palpitations/), [Excessive Sweating](/symptoms/excessive-sweating/), [Feeling Anxious](/symptoms/feeling-anxious/), [Difficulty Sleeping](/symptoms/difficulty-sleeping/), or [Diarrhoea](/symptoms/diarrhoea/). Symptoms can overlap with other illnesses, so their presence does not establish the diagnosis.

Contact a clinician promptly for symptoms that are new, worsening, or affecting daily activity. Bring a list of medicines, supplements, thyroid treatment, and recent illness. Avoid taking extra thyroid medicine or changing a prescribed dose without advice. Rest, drink fluids if you can, and avoid strenuous exertion while waiting for assessment. A clinician may check your pulse, blood pressure, temperature, thyroid hormone levels, and heart rhythm.

Call emergency services for chest pain, severe breathlessness, fainting, severe agitation, confusion, collapse, or a very fast or irregular heartbeat. A high temperature with marked weakness, vomiting, or altered awareness is also an emergency because a sudden severe thyroid reaction can become dangerous quickly. Do not drive yourself if you feel faint or confused. [Night Sweats](/symptoms/night-sweats/) or [Heat Intolerance](/symptoms/heat-intolerance/) alone still deserve routine assessment when persistent.

Ask what may have triggered the change, how your heart will be monitored, whether your treatment needs adjustment, and which symptoms should prompt immediate return.