What iodine can you take orally: Sources, supplements, and safety

January 7, 2026 •

4 min read

Worldwide, approximately 2 billion people are affected by iodine deficiency, making it the most common preventable cause of intellectual and developmental disabilities. The human body cannot produce this essential trace mineral, so it must be obtained through the diet or supplementation.

Quick Summary

Both food sources and dietary supplements offer options for oral iodine intake. Forms range from common iodized table salt and kelp to specific medical preparations like potassium iodide and Lugol's solution, used for deficiency or under professional guidance.

Key Points

Dietary Sources: Excellent food sources of oral iodine include iodized salt, fish, dairy products, and seaweed.
Supplement Forms: Oral supplements are typically available as potassium iodide (KI) or as kelp-based products, with dosage and source stability varying significantly.
Thyroid Protection: For specific medical or emergency situations, like radiation exposure, potassium iodide (KI) can protect the thyroid from absorbing radioactive iodine.
Medical Preparations: Stronger solutions, such as Lugol's iodine, are used for specific conditions like thyrotoxicosis and must only be taken under strict medical supervision.
Regulation and Risk: Both too little and too much iodine can cause thyroid problems, including goiter, emphasizing the need for professional medical advice before taking supplements.
Inconsistent Sources: The iodine content in natural sources like kelp can be highly variable, making supplements from these sources potentially unreliable and risky for excessive intake.

Dietary Sources of Oral Iodine

For most people, meeting the recommended daily allowance of iodine is best achieved through a balanced diet. The iodine content in food can be highly variable, depending on the mineral content of the soil where the food was grown. However, some food categories are consistently good sources.

Iodized Salt

Since the 1920s, the fortification of table salt with iodine has been a cornerstone of public health efforts to combat iodine deficiency. While most household table salt in countries like the U.S. is iodized, specialty salts such as sea salt or kosher salt are not always fortified. Furthermore, manufacturers often use non-iodized salt in processed foods, so relying solely on packaged goods for iodine is unwise.

Seafood and Dairy

Foods from the ocean naturally contain high amounts of iodine, as marine life concentrates the mineral from seawater. This includes fish like cod and tuna, as well as shellfish like shrimp and oysters. Dairy products are another significant source of iodine. The iodine content in milk, cheese, and yogurt can vary based on the feed given to cows and the cleaning agents used in milking equipment.

Seaweed and Kelp

Among all foods, seaweed is one of the richest natural sources of iodine. Popular varieties include kombu, wakame, and nori. However, the iodine content can fluctuate dramatically between different species and preparation methods. Brown seaweeds like kelp, in particular, can contain very high concentrations, sometimes exceeding safe intake levels. For this reason, using seaweed as a supplement source requires caution, and some health organizations advise against it due to the risk of excessive intake.

Oral Iodine Supplements

For individuals with dietary restrictions or diagnosed deficiencies, supplements can provide a reliable source of iodine under medical supervision. These are available in various forms and potencies.

Potassium Iodide (KI)

Potassium iodide is a common and widely available form of iodine supplement. It is used for standard supplementation and has specific, medically approved uses, such as protecting the thyroid gland from radioactive iodine in a radiation emergency. The FDA has approved KI products like ThyroSafe and Iosat for this purpose, emphasizing they should only be used as directed by public health officials. KI is available in both tablet and liquid forms.

Lugol's Solution

Lugol's solution is a composite iodine solution containing a mixture of elemental iodine and potassium iodide. While it is available over the counter, it is typically used for specific medical purposes under a doctor's supervision, such as treating thyrotoxicosis or preparing the thyroid for surgery. It has a metallic taste and can irritate the gastrointestinal tract, so it should be diluted with water or juice before consumption.

Kelp Supplements

Derived from seaweed, kelp supplements are often marketed as a natural iodine source. However, the iodine content can be highly inconsistent and may exceed safe levels, potentially causing thyroid dysfunction. Due to this variability and the risk of over-consumption, many dietetic associations recommend against using them as a reliable source of iodine.

Oral Iodine Comparison Table


Oral Iodine Source	Typical Form	Primary Use	Safety Consideration
Iodized Salt	Granular salt	Everyday dietary intake	Must be used consistently; non-iodized versions are common in processed foods.
Seafood/Dairy	Whole foods	Dietary intake	Content can vary; often insufficient for those with severe deficiency.
Seaweed/Kelp	Whole food, supplements	Dietary intake, supplementation	Highly variable iodine content; risk of excessive intake, especially with kelp.
Potassium Iodide	Tablets, liquid	Supplementation, radiation protection (medical use)	Use only under medical supervision; specific protocols for emergencies.
Lugol's Solution	Liquid drops	Medical treatment (hyperthyroidism)	Strong concentration requires medical guidance and dilution.

Potential Risks and Safe Intake

While iodine is essential, consuming too much can also cause health problems, including elevated TSH levels, goiter, and hypothyroidism, symptoms similar to a deficiency. The tolerable upper intake level (UL) for iodine is 1,100 mcg daily for adults. For special populations like pregnant or breastfeeding women, the recommended intake is higher, but the UL should be discussed with a healthcare provider. Some individuals, including those with autoimmune thyroid disease, are particularly sensitive to high iodine intake. It is important to remember that dietary sources are different from high-dose medical treatments, which must be managed by a doctor.

Conclusion

Oral iodine intake is crucial for thyroid function and overall health, especially for fetal and cognitive development. It can be obtained through a variety of dietary sources, including iodized salt, seafood, and dairy. For those who cannot get enough from their diet, supplements in the form of potassium iodide, or regulated kelp products, are available under medical guidance. However, the risk of both deficiency and excessive intake necessitates a careful, medically informed approach. High-dose preparations like Lugol's solution and KI for radiation emergencies should only be used as directed by a healthcare professional due to potential side effects. Prioritizing dietary intake and consulting a doctor for any supplementation is the safest path to maintaining optimal iodine levels.

The Importance of Medical Guidance

Because iodine intake affects the delicate balance of thyroid hormones, it is critical to consult with a healthcare provider before beginning any supplementation, especially high-dose options. A doctor can help determine if there is a true deficiency and recommend the appropriate type and dosage to avoid adverse effects. For instance, certain populations are more susceptible to the risks of excess iodine, including pregnant women, newborns, and individuals with pre-existing thyroid conditions. For more information on iodine requirements and safety, refer to authoritative sources like the NIH Office of Dietary Supplements.

Frequently Asked Questions

For most of the world's population, the primary source of iodine comes from iodized salt, which is table salt fortified with small amounts of potassium iodide.

No, table salt and other food sources do not contain nearly enough iodine to block the thyroid's absorption of radioactive iodine during an emergency. Only FDA-approved potassium iodide (KI) products should be used, and only as directed by officials.

Iodine is the elemental form, while iodide is the salt form of iodine. Dietary supplements typically contain potassium iodide or sodium iodide, and the body readily absorbs iodide.

Excessive intake can cause thyroid problems, including elevated TSH levels, goiter, and hyperthyroidism. The tolerable upper intake level (UL) for adults is 1,100 mcg daily, and taking higher doses long-term should be done only under medical supervision.

Pregnant women, people on vegan diets, individuals who do not use iodized salt, and those living in areas with iodine-deficient soil are at a higher risk of deficiency.

The iodine content in seaweed, particularly kelp, can vary drastically depending on the species, harvest location, and preparation, leading to inconsistent dosing and a risk of consuming excessive amounts.

Oral inorganic iodine can be used to treat Graves' disease or thyroid storm under strict medical supervision, but it can also induce or worsen hyperthyroidism in some cases. Therefore, it is crucial to consult a doctor before use.