Why is my TSH high, and what does it feel like?
A high TSH usually means the thyroid is underperforming and the pituitary is pushing it harder, but several ordinary things raise the number without any thyroid disease at all.
The common causes, most likely first: an autoimmune thyroid, which is Hashimoto's and is found with a thyroid antibody test; too low a dose of thyroid medicine if you already take it; recovery from any recent illness, which lifts TSH for weeks; some medicines, including lithium and amiodarone; and a biotin supplement, which does not raise TSH but makes the assay read wrong, so stop it several days before a repeat test.
What it feels like when it is the real thing: tiredness that sleep does not fix, feeling cold when others do not, constipation, dry skin, weight gain, heavier periods and slowed thinking. Mild elevations often cause nothing at all, which is why the number is repeated in six to twelve weeks with antibodies before anyone commits to lifelong tablets.
For what each TSH value means, band by band, the full guide has the table.
See a doctor promptly if
- Drowsiness, confusion or slow breathing in someone known to have an underactive thyroid. This needs emergency care.
- Very low body temperature with slowed thinking and extreme tiredness
- A resting heart rate under 50 beats per minute with dizziness or fainting
- New neck swelling, trouble swallowing, or a hoarse voice lasting over three weeks
- A high TSH found during pregnancy or while trying to conceive
- New chest pain or a racing heartbeat after starting thyroid hormone replacement
What your TSH number means
| Result | In short | What it means |
|---|---|---|
| Under 0.4 mIU/L | Low | Suggests an overactive thyroid rather than an underactive one, or too high a dose of thyroid medicine. Needs free T4 alongside it. |
| 0.4 to 4.0 mIU/L | Normal | The usual adult range, though labs differ slightly and pregnancy has its own narrower targets. Symptoms with a normal TSH usually have another cause. |
| 4.1 to 6.9 mIU/L | Mildly high | Often nothing. Recent illness, a poor night, biotin supplements and even the time of day move it. The standard next step is a repeat in six to twelve weeks with thyroid antibodies. |
| 7.0 to 9.9 mIU/L | High | Still called subclinical if free T4 is normal. Whether it is treated depends on symptoms, antibodies, age and whether you are trying to conceive. |
| 10.0 to 19.9 mIU/L | Clearly high | Most guidelines treat at this level even without symptoms, because the progression rate to full underactivity is high. |
| 20 mIU/L and above | See a doctor | Usually established hypothyroidism, and often with a low free T4. Treatment is straightforward and the number is followed until it settles. |
| Any value, in pregnancy | Different rules | Targets are lower and act sooner. A TSH that would be watched in anyone else is treated promptly in pregnancy. |
One result is a snapshot. Ranges differ a little between labs, and what a number means depends on the rest of you. Check it against the guidelines.
Try the result lookupone number, free, nothing to installType the number you are holding and it lands in a band, with what usually happens next.
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Answered by the AskDoc Medical Team · Medically reviewed under our Medical Director, MBBS · How we review
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