Your Questions About Underactive Thyroid, Answered
Underactive Thyroid: straight answers to the questions people actually ask, with the figures behind them.
Hypothyroidism: the thyroid producing too little hormone, slowing many body processes.
Key takeaways
- Main test: TSH, with free T4 if abnormal
- Pattern: raised TSH with low T4
- Most useful single change: Take levothyroxine on an empty stomach at the same time daily.
- Commonest mistake: Taking it with breakfast, coffee or supplements.
- See a doctor if any of the signs under "When to speak to a doctor" below apply to you.
What is Underactive Thyroid?
Hypothyroidism: the thyroid producing too little hormone, slowing many body processes.
Why does it matter?
Symptoms are vague and easily attributed to ageing, stress or low mood, and the treatment is a single cheap daily tablet.
Main test for Underactive Thyroid?
TSH, with free T4 if abnormal.
How to take it for Underactive Thyroid?
On an empty stomach, 30-60 minutes before food.
Retest after a dose change for Underactive Thyroid?
Usually 6-8 weeks.
What is the single most useful thing to do?
Take levothyroxine on an empty stomach at the same time daily.
What is the most common mistake?
Taking it with breakfast, coffee or supplements.
When should I see a doctor?
See a GP promptly if you become pregnant while taking levothyroxine, as the dose usually needs increasing immediately. Seek urgent help for extreme drowsiness, confusion, very low body temperature or collapse, which can indicate severe untreated hypothyroidism. Report palpitations, tremor or weight loss, which can indicate over-replacement.
Where to go next
- Starting Out With Underactive Thyroid
- Underactive Thyroid at a Glance
- Underactive Thyroid — the reference entry
- Overactive Thyroid: Sorting the Evidence From the Noise
- What the Guidance Really Says About Thyroid Function Tests
When to speak to a doctor
See a GP promptly if you become pregnant while taking levothyroxine, as the dose usually needs increasing immediately. Seek urgent help for extreme drowsiness, confusion, very low body temperature or collapse, which can indicate severe untreated hypothyroidism. Report palpitations, tremor or weight loss, which can indicate over-replacement.
Where this comes from
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarised or generalised beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to a GP, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 999.
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