Lithium-Induced Thyroid Dysfunction
Lithium is an effective mood-stabilising medicine, but it affects the thyroid in a significant proportion of people who take it. The most common effects are an enlarged thyroid and an underactive thyroid; overactivity occurs less often.
Because lithium is often essential, the thyroid problem is usually managed alongside it rather than by stopping the drug.
Last medically reviewed: 15 November 2025
Key points
- Lithium commonly causes goitre and hypothyroidism, and less often hyperthyroidism.
- Thyroid function should be checked before starting lithium and monitored regularly.
- Hypothyroidism on lithium is treated with levothyroxine while lithium usually continues.
- Never stop lithium suddenly without advice from the prescribing team.
How lithium affects the thyroid
Lithium is concentrated by the thyroid and can interfere with hormone production and release. It also stimulates the gland to enlarge, which is why goitre is common.
The effects can develop gradually and are often picked up on routine monitoring before symptoms appear.
Monitoring
Thyroid function is usually checked before starting lithium and then at regular intervals — commonly every six to twelve months, or sooner if symptoms develop. Calcium is sometimes monitored too because lithium can affect the parathyroid glands.
Symptoms such as fatigue, weight gain, cold intolerance, palpitations or neck swelling should prompt earlier testing.
Management
An underactive thyroid is treated with levothyroxine while lithium continues. The dose is adjusted according to TSH, and monitoring continues at intervals.
Overactive thyroid on lithium is less common and needs specialist assessment; treatment depends on the mechanism and on the psychiatric plan.
Working with your team
Thyroid changes on lithium are best managed jointly by the prescribing psychiatric team, the thyroid clinician and, where relevant, the GP. Stopping lithium abruptly can destabilise mood, so decisions are made together.
When to seek urgent medical help
- Severe tremor, confusion, vomiting or unsteadiness — possible lithium toxicity.
- Palpitations with chest pain or breathlessness.
- Marked neck swelling causing difficulty breathing or swallowing.
This guidance does not replace emergency services. If you are seriously unwell, seek urgent medical care immediately.
Frequently asked questions
Does lithium always affect the thyroid?
No, but thyroid effects are common enough that regular monitoring is recommended for everyone taking lithium.
Do I have to stop lithium?
Usually not. Thyroid problems can be managed while lithium continues. Any change to lithium should be discussed with your prescribing team.
Can lithium cause hyperthyroidism?
It can, though less commonly than hypothyroidism. The cause and treatment are assessed in the usual way.
How often should my thyroid be checked?
Typically before starting and then every six to twelve months, or sooner if you develop symptoms.
References & further reading
This page is based on established medical knowledge and guidelines from authoritative sources. Always consult a qualified clinician for personal medical advice.
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