The daily iodine amount your thyroid needs
Most adults need 150 micrograms of iodine per day to keep the thyroid working properly. That is the recommendation from the National Institutes of Health and is the amount set as the Recommended Dietary Allowance (RDA) in the United States. Your thyroid uses iodine to make thyroid hormones, which control metabolism, body temperature, and energy — so without enough iodine, your thyroid cannot do its job.
The amount you need does not change much across your life, but it does shift at certain points. Pregnant people need 220 micrograms daily, and people who are breastfeeding need 290 micrograms daily, because iodine passes to the baby through the placenta and breast milk. Children need less: ages 1 to 8 need 90 micrograms, and ages 9 to 13 need 120 micrograms.
Most people in the United States get enough iodine without thinking about it, because table salt is iodized — one-quarter teaspoon of iodized salt contains roughly 75 micrograms. If you eat processed foods, you are likely getting iodine from the salt in those products. If you use sea salt, kosher salt, or non-iodized salt, you need to get iodine from food or a supplement instead.
Key Takeaways
- Adults need 150 micrograms of iodine daily; pregnant and breastfeeding people need more.
- Iodized table salt is the main source of iodine for most Americans, but sea salt and kosher salt do not contain iodine unless labeled.
- Dairy, eggs, seafood, and seaweed are natural food sources of iodine, though amounts vary widely by region and farming practices.
- Too much iodine can cause thyroid problems just as too little can, so more is not better.
Where iodine comes from in food
Iodized salt is the easiest source, but it is not the only one. Dairy products, eggs, and seafood naturally contain iodine because animals eat iodine-containing feed or water. A single large egg has roughly 16 to 20 micrograms. A cup of milk has about 56 micrograms. Fish and shellfish vary widely — cod has more than 60 micrograms per 3-ounce serving, while shrimp has less.
Seaweed is extremely high in iodine, but the amount is unpredictable. Some seaweed snacks contain 16 micrograms per sheet; others contain 2,000 micrograms or more. This unpredictability makes seaweed risky as a regular iodine source unless you know the exact content of the product you are eating.
Vegetables, grains, and meat contain iodine only if the soil where they grew had iodine in it. In regions where soil is iodine-poor — parts of Europe, Asia, and South America — people who do not use iodized salt are at risk for iodine deficiency. In the United States, soil iodine levels are generally adequate, so vegetables and grains grown here usually contain some iodine.
When you might need more or less iodine
Pregnancy and breastfeeding are the clearest reasons to increase iodine intake. The developing fetus and newborn depend entirely on maternal iodine to build their brains and nervous systems. Iodine deficiency during pregnancy can cause permanent intellectual disability in the child, which is why prenatal vitamins in the United States include iodine.
Certain medications and conditions can interfere with iodine absorption or use. Some antithyroid drugs used to treat Graves' disease block iodine uptake. Lithium, used for bipolar disorder, can reduce thyroid function. If you take either of these medications, your doctor may monitor your iodine status or thyroid function more closely.
People with cystic fibrosis may have trouble absorbing iodine and may need supplementation. People following a strict vegan diet without iodized salt or supplements may not get enough iodine, since plant foods are unreliable sources. If you fall into any of these groups, talk with your doctor or a registered dietitian about whether you need additional iodine.
The risk of too much iodine
More iodine is not better. The upper limit for iodine intake is 1,100 micrograms per day for adults. Consuming more than this regularly can cause thyroid problems, including hypothyroidism (an underactive thyroid) and autoimmune thyroid disease. This is called iodine-induced hypothyroidism and is more common in people who already have thyroid disease or a family history of it.
High iodine intake can also trigger or worsen Graves' disease in susceptible people. Some supplements, kelp products, and certain medications (like some heart drugs and cough syrups) contain very high amounts of iodine. If you are taking supplements or using kelp regularly, check the iodine content and discuss it with your doctor.
Iodine supplements: when and how to use them
Most people do not need an iodine supplement if they use iodized salt or eat dairy and eggs regularly. Prenatal vitamins contain iodine as standard, so pregnant people are usually covered. If you follow a vegan diet, use only non-iodized salt, and do not eat seaweed or iodine-fortified foods, a supplement may make sense.
Iodine supplements come as potassium iodide or sodium iodide, usually in doses of 75 to 150 micrograms. They are inexpensive and available without a prescription. If you are considering a supplement, start by talking with your doctor, especially if you have a history of thyroid disease, take medications that affect iodine, or live in a region where iodine deficiency is common.
How to know if you are getting enough
The most reliable way to check iodine status is a urine test, which measures iodine excretion. A 24-hour urine collection is the gold standard, though some labs use a single spot urine sample. Your doctor can order this test if you have symptoms of thyroid disease or if you are pregnant and your doctor wants to confirm adequate iodine intake.
Thyroid function tests (TSH and free T4) do not directly measure iodine status, but they can show whether your thyroid is working properly. If your thyroid function is normal and you are eating a reasonably varied diet with some salt, dairy, or eggs, you are almost certainly getting enough iodine. If you have symptoms like fatigue, weight gain, or cold intolerance, or if you are planning pregnancy, ask your doctor whether iodine testing makes sense for you.
Frequently Asked Questions
Can iodine supplements help with weight loss or energy?
No. Iodine supplements will not boost weight loss or energy unless you actually have iodine deficiency, which is rare in the United States. If your thyroid is working normally, adding more iodine will not speed up your metabolism. If you are fatigued or gaining weight, the cause is usually something other than iodine deficiency, and a doctor should investigate.
Is sea salt a good source of iodine?
No. Sea salt contains very little iodine naturally, even though it comes from the ocean. Unless the label says it is iodized, sea salt will not provide meaningful iodine. If you prefer sea salt or kosher salt, you will need to get iodine from other foods or a supplement.
What happens if I get too much iodine from supplements?
Regularly consuming more than 1,100 micrograms per day can cause thyroid inflammation, hypothyroidism, or autoimmune thyroid disease, especially in people with existing thyroid conditions. This is why it is important to check the iodine content of any supplement you take and not exceed the recommended amount without medical guidance.
Do I need more iodine if I have hypothyroidism?
Not necessarily. If your hypothyroidism is caused by iodine deficiency, then yes — but in the United States, most hypothyroidism is caused by Hashimoto's disease, an autoimmune condition. Taking extra iodine when you have Hashimoto's can actually make the condition worse. Your doctor should determine the cause of your hypothyroidism before you change your iodine intake.