Quick answer

Ask your pharmacist or doctor before combining. The lithium label lists iodide preparations as an interaction that may produce an underactive thyroid, and the potassium iodide label warns the same. NIH says many multivitamins contain iodine, often 150 mcg, so check every label you use.^1,2,3

Key facts

The lithium label gives iodide preparations a row of their own among interacting medicines and says using them together may produce hypothyroidism, an underactive thyroid.¹
The potassium iodide label says use with lithium or antithyroid drugs may potentiate their underactive-thyroid and goiter-forming effects.²
The lithium label says lithium is concentrated in the thyroid and can inhibit thyroid hormone synthesis and release on its own.¹
MedlinePlus lists lithium among the medicines that can cause an underactive thyroid.⁴
NIH says iodine in supplements is often potassium iodide or sodium iodide, and that kelp supplements contain iodine too.³

Ask your pharmacist or doctor first

Iodide taken with lithium may lower thyroid function. The lithium label lists iodide preparations as an interaction and asks prescribers to watch for an underactive thyroid, and the potassium iodide label gives the same warning.^1,2

On the medicine's label

What do the lithium and potassium iodide labels say?

Both labels are written for prescribers and make the same point from two directions. Under drug interactions, the lithium label gives iodide preparations a row of their own: using them together may produce hypothyroidism, and prescribers should monitor for its signs or symptoms. The potassium iodide solution label says that using it at the same time as lithium or antithyroid drugs may potentiate their underactive-thyroid and goiter-forming effects, meaning the effects may add up.^1,2

The labels name iodide preparations, not one particular product, and neither gives an amount of iodide at which the concern begins. NIH's iodine fact sheets list other medicine interactions but do not include lithium among their examples, so the warning here rests on the two labels.^1,2,3

How does lithium affect the thyroid by itself?

The lithium label has a separate warning about the thyroid. It says lithium is concentrated within the thyroid and can inhibit the making and release of thyroid hormone, which can lead to an underactive thyroid, and that some cases of an overactive thyroid have been reported as well. It asks prescribers to check thyroid function before treatment starts and again at set intervals while it continues. MedlinePlus also lists lithium among the medicines that can cause an underactive thyroid.^1,4

That is why the pairing is flagged. The thyroid is already a place where lithium acts, and iodide acts there too. MedlinePlus lists the early symptoms of an underactive thyroid as constipation, feeling cold, tiredness or feeling slowed down, paleness or dry skin, thin brittle hair or nails, weakness and weight gain.⁴

Where does iodine turn up in supplements?

Of 89 best-selling US adult multivitamins, 74% contained iodine, with a median of 150 mcg per daily serving, all as potassium iodide. Of 59 prenatal vitamins, 34 contained iodine, from 25 to 290 mcg, and about a quarter of those used kelp.⁵

NIH says iodine in supplements is often present as potassium iodide or sodium iodide, and that kelp, a seaweed that contains iodine, is also sold as a supplement. Many multivitamin and mineral products contain iodine, often 150 mcg, and some prenatal products do too, while iodine-only products can hold high amounts, sometimes above the upper limit.³

The lithium and potassium iodide labels discuss iodide preparations, not food. The sources checked do not address iodized salt or seaweed in meals. That is not a finding either way, so ask your pharmacist.^1,2

Does lithium orotate change the question?

The lithium label read for this page covers lithium carbonate, a prescription medicine. The sources checked do not address lithium orotate sold as a supplement. That is not a finding either way, so tell your pharmacist or doctor about any lithium product you take, whether prescribed or not.¹

What to ask your pharmacist about iodine and lithium

Do any of my supplements contain iodine, potassium iodide or kelp?
How often is my thyroid checked while I take lithium, and should a new iodine product change that?
Which symptoms of an underactive thyroid should I report to you?
Is the iodine in my multivitamin something I should mention, or does it need to change?

Questions people ask

Can you take iodine with lithium?

Ask your pharmacist or doctor first. The lithium label lists iodide preparations as an interaction that may produce an underactive thyroid.¹

What are the iodine and lithium interactions?

The sources read for this page describe one: iodide with lithium may lower thyroid function. The lithium label lists other interactions with different medicines, such as diuretics and anti-inflammatory pain relievers.¹

What about iodine and lithium orotate?

The lithium label covers lithium carbonate. The sources checked do not address lithium orotate supplements, so ask your pharmacist.¹

Does lithium affect the thyroid?

Yes. The label says lithium is concentrated in the thyroid and can lead to an underactive thyroid, and it asks prescribers to monitor thyroid function.¹

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.