Can you get too much iodine from table salt?

December 4, 2025 •

4 min read

The Tolerable Upper Intake Level (UL) for iodine is 1,100 micrograms per day for adults. While iodized salt has been instrumental in preventing deficiency, many wonder, can you get too much iodine from table salt and risk health issues?

Quick Summary

It is highly improbable for healthy individuals to exceed the safe iodine limit solely from iodized table salt. Excess iodine exposure is more likely from supplements or specific foods like seaweed, which can affect thyroid function in vulnerable groups. Standard iodized salt use is generally not a concern for iodine overload, but total salt intake should be monitored.

Key Points

Sodium limit is reached first: You would consume an unsafe amount of sodium from table salt long before you could ingest a dangerous amount of iodine.
Tolerable Upper Intake Level: The adult UL for iodine is 1,100 mcg per day, while the RDA is only 150 mcg.
Excess from other sources: Most cases of iodine overload result from high-dose supplements or the overconsumption of very rich natural sources like certain seaweeds.
Affects susceptible groups: Excessive iodine can trigger or worsen thyroid problems, especially in those with pre-existing conditions or in the elderly.
Check all sources: Total iodine intake from fortified foods, supplements, and iodine-rich foods should be considered to avoid potential harm.
Thyroid dysfunction risk: High iodine intake can lead to both hyperthyroidism and hypothyroidism in vulnerable individuals.

Understanding Iodine: The Essential Mineral

Iodine is a trace element that is vital for human health, primarily because it is a key component of thyroid hormones. These hormones, which include thyroxine ($T_4$) and triiodothyronine ($T_3$), regulate metabolism, protein synthesis, and growth. The body cannot produce its own iodine, so it must be obtained through the diet.

To ensure public health and prevent iodine deficiency disorders like goiter, salt iodization programs were introduced globally. However, this has led to questions about potential overconsumption.

Recommended Intake and Upper Limits

To maintain a healthy balance, it's important to understand the recommended dietary allowance (RDA) and the tolerable upper intake level (UL) for iodine.

Adults (19+ years): The RDA is 150 micrograms (mcg) per day.
Pregnant women: The RDA is higher, at 220 mcg per day, to support fetal development.
Lactating women: These women have an even higher RDA of 290 mcg per day.
Tolerable Upper Intake Level (UL) for adults: 1,100 mcg per day. Consistently exceeding this amount can lead to adverse health effects, particularly on the thyroid.

The Role of Table Salt in Iodine Intake

Iodized table salt is a significant source of dietary iodine for many people, but the amount added is carefully regulated. Typically, a quarter-teaspoon of iodized salt contains approximately 71-78 mcg of iodine.

Here’s how the numbers break down for a typical adult:

Daily RDA (150 mcg): Easily met by consuming a little more than half a teaspoon of iodized salt.
Daily UL (1,100 mcg): To reach this limit from table salt alone, an adult would need to consume around 4 to 6 teaspoons of iodized salt in a single day.

The World Health Organization (WHO) recommends limiting total daily salt intake to less than 5 grams, which is about one teaspoon. This amount provides adequate iodine without excessive sodium. The key takeaway is that you would almost certainly exceed the safe limit for sodium long before you reached the iodine UL from iodized salt alone.

Other Dietary Sources of Iodine

Iodized salt is not the only source of iodine in our diets. Many foods naturally contain this mineral, and others are fortified. For those monitoring their intake, especially vulnerable populations, it’s crucial to be aware of all potential sources.

Common sources of iodine include:

Dairy products: Milk, yogurt, and cheese are often good sources, partly due to iodine-containing disinfectants used on milking equipment.
Seafood: Fish, shrimp, and other shellfish naturally concentrate iodine from seawater.
Seaweed: This is one of the richest sources of iodine, with varieties like kelp containing significantly more than the daily UL in small servings. This is a major cause of excess iodine intake in populations that consume a lot of seaweed.
Eggs: A good source of iodine, particularly in the yolk.
Iodine supplements: These are often concentrated and can easily lead to excessive intake, especially when taken without medical supervision.

Risks of Excessive Iodine Intake

While the body can typically regulate excess iodine for a time, consistently high intake can lead to serious health problems. The thyroid's homeostatic mechanisms, designed to prevent overstimulation, can fail.

Potential Health Issues

Thyroid Dysfunction: High iodine levels can trigger both hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid).
Autoimmune Thyroid Diseases: In susceptible individuals, high iodine can provoke or worsen conditions like Hashimoto's thyroiditis and Graves' disease.
Goiter Formation: An enlarged thyroid gland can result from both iodine deficiency and excess.
Acute Toxicity: Extremely large, single doses of iodine (several grams, usually from supplements or medications) can cause acute poisoning with symptoms like burning sensations, fever, and digestive issues.

Individuals at Higher Risk

Certain populations are more sensitive to the effects of excess iodine and should be especially cautious:

People with pre-existing thyroid disease: Individuals with autoimmune thyroid conditions are particularly vulnerable to iodine-induced problems.
The elderly: This group may have impaired thyroid regulatory mechanisms.
Developing fetus and neonates: Excess iodine intake during pregnancy can pose risks to the baby.
People in historically iodine-deficient regions: Introducing iodized salt to these populations can cause a temporary spike in hyperthyroidism as thyroids adapt.

Iodized Salt vs. Other Iodine Sources: A Comparison

To put the risks into perspective, here is a comparison of typical iodine sources.


Source	Iodine Content	Risk of Excess from Typical Use
Iodized Table Salt	Approx. 75 mcg per ¼ tsp	Very low; sodium limit is reached first.
Seaweed (e.g., Kombu kelp)	Can be over 1,000 mcg per gram	High; a small amount can exceed the UL.
Milk (1 cup)	Approx. 85 mcg	Low; would need excessive consumption.
Iodine Supplements	Often 150+ mcg per dose	Moderate to High; easy to exceed UL without awareness.

Conclusion

For the average person, it is not possible to get too much iodine from table salt alone, as the amount fortified is minimal compared to the safe upper intake level. The main health concern regarding table salt is the risk of excessive sodium, not iodine. The primary sources of iodine overload are supplements, certain medications, or diets that include large quantities of iodine-rich foods, particularly seaweed. Individuals with pre-existing thyroid conditions, the elderly, and pregnant women should be more mindful of their total iodine intake from all sources and should consult a healthcare provider if they have concerns. Maintaining a balanced and varied diet remains the best approach to ensuring adequate but not excessive iodine intake. For more information on dietary minerals, refer to the NIH Office of Dietary Supplements.

Frequently Asked Questions

To reach the adult Tolerable Upper Intake Level (UL) of 1,100 micrograms of iodine, you would need to consume about 4 to 6 teaspoons of iodized salt in one day, which far exceeds the recommended daily sodium intake.

The most common sources of excessive iodine intake are dietary supplements, certain medications (like amiodarone), and natural foods, with seaweed being a particularly rich and potent source.

Yes, excessive iodine intake can cause or worsen thyroid problems, including both hyperthyroidism and hypothyroidism. It is particularly risky for people with pre-existing thyroid conditions, such as autoimmune thyroid disease.

Symptoms of acute iodine toxicity from very high doses can include a burning sensation in the mouth and throat, fever, stomach pain, nausea, vomiting, diarrhea, and a weak pulse.

Individuals most vulnerable to the effects of excess iodine include those with underlying thyroid conditions, the elderly, fetuses and neonates, and people living in regions with high natural iodine content in the water and food supply.

No, not all salt is iodized. Only salt explicitly labeled as 'iodized' has added iodine. Other salts, such as sea salt, Himalayan pink salt, and kosher salt, typically do not contain iodine unless it is added.

If you don't use iodized salt, you can get iodine from other food sources like seafood and dairy products. If you are concerned about your intake, you can speak with a healthcare provider or dietitian. They may recommend monitoring your intake or taking a supplement.