What should you know about hypothyroidism fatigue?

When thyroid hormone is too low, body processes can slow. A person may feel drained, sleepy in the daytime, mentally slowed, unusually cold, constipated, weak, or less able to manage ordinary activity. Fatigue can also follow poor sleep, stress, infection, anaemia, mood conditions, medication effects, or other health problems. These possibilities are why symptoms are assessed together rather than used as a diagnosis. See [Hypothyroidism](/conditions/hypothyroidism/).

If hypothyroidism has already been diagnosed, fatigue may mean the treatment plan needs review, but it may also have a separate cause. Do not increase thyroid medicine yourself. Keep track of sleep, activity, meals, mood, and when tiredness is worst.

Arrange a routine appointment when fatigue lasts, limits work or daily tasks, or comes with weight change, cold intolerance, constipation, hair or skin changes, or muscle weakness. Bring your medicine and supplement list, describe missed doses or timing changes, and mention recent illness, bleeding, pregnancy, or major sleep disruption when relevant. Regular sleep and gentle activity can be useful while you await review, with rest balanced against long periods of inactivity.

Seek urgent help if tiredness comes with chest pain, severe shortness of breath, fainting, new confusion, one-sided weakness, or inability to stay awake. A sudden major change needs prompt assessment. Do not assume severe symptoms are simply due to an underactive thyroid.

Ask whether thyroid function testing is needed, whether another blood test or sleep assessment could help, and whether your medicine is being taken at the right time. Ask how to monitor progress and what change should prompt an earlier review.