Iodine Deficiency and Iodized Salt: Iodine Needs in Pregnancy

Short Answer

Adults need 150 µg of iodine per day; in pregnant and breastfeeding women this rises to 200–250 µg. A healthy adult can usually meet this need with iodized table salt and food; in Türkiye, iodization of table salt is mandatory. According to the TEMD 2025 guideline (Society of Endocrinology and Metabolism of Turkey), deficiency is still common among pregnant women, and the guideline recommends supplementation for them in addition to iodized salt. Too much iodine is also harmful; seaweed (kelp) tablets can cause problems, especially in people with thyroid disease.

What does it do?

Iodine is the building block of the thyroid hormones T4 and T3. These hormones regulate growth, development and metabolism. Iodine contributes to the normal production of thyroid hormones and to normal thyroid function.

According to TEMD 2025, iodine deficiency is the most important cause of preventable intellectual disability worldwide. Deficiency can affect the brain development of the baby in the womb. In adults, it can lead to goiter and hypothyroidism.

Daily requirement

The requirement varies with age and pregnancy-breastfeeding status. The values are for healthy people.

Group	Daily iodine	Source
Adults and over 12 years	150 µg	TÜBER 2022; WHO 2007
Pregnant and breastfeeding	200 µg	TÜBER 2022
Pregnant and breastfeeding	250 µg	WHO 2007
Children 6–12 years	120 µg	WHO 2007
0–59 months	90 µg	WHO 2007

In short, the daily requirement rises to 200–250 µg in pregnancy and breastfeeding. In the US, the NIH recommends 220 µg for pregnancy and 290 µg for breastfeeding. The figures vary somewhat by institution; all show that the requirement increases in pregnancy.

Which foods contain it?

According to TÜBER 2022 (Türkiye's national dietary guidelines), the main sources of iodine are iodized salt and seafood:

• Iodized table salt: Under the Turkish Food Codex, adding 25–40 mg of potassium iodate per kilogram of table salt is mandatory. TEMD 2025 assumes that a pregnant woman using standard iodized salt gets an average of 100–150 µg of iodine per day.
• Fish: TÜBER 2022 considers sea fish in particular a good source of iodine.
• Dairy products and eggs: The NIH also lists these among good sources.
• Vegetables and fruit: Usually a poor source, depending on the soil.

Cutting down on salt and getting iodine do not conflict. TÜBER 2022 recommends keeping daily salt below 5 g in adults and using iodized salt.

Who is at risk of deficiency?

• Pregnant and breastfeeding women: The requirement increases. According to TEMD 2025, the median urinary iodine in 3,543 pregnant women in Istanbul was 77 µg/L. According to the WHO, a median below 150 µg/L in pregnant women indicates that iodine intake in that population is insufficient. This is a population indicator; it does not show the status of individual people.
• People living in rural areas: In the 2007 survey cited by TEMD 2025, urinary iodine was at a moderate-to-severe deficiency level in 27.8% of schoolchildren. Median urinary iodine was 42 µg/L in rural schools and 147 µg/L in cities.
• People using non-iodized salt: Those who prefer rock salt or non-iodized salt.
• People who cut out salt entirely: Risk increases if there is no other source of iodine.

Symptoms: Swelling in the neck (goiter), fatigue, feeling cold, weight gain and constipation, which are signs of an underactive thyroid, may occur. These symptoms also have other causes. On their own they do not indicate iodine deficiency.

Which test, and how to read it?

There is no reliable routine blood test that shows iodine deficiency in an individual. Urinary iodine measurement was developed for population surveys. According to TEMD 2025, a single spot or 24-hour urine sample does not show an individual's iodine status. For a personal assessment, at least 10 samples on different days are needed.

Instead, your physician looks at thyroid function:

• TSH and free T4
• Anti-TPO if needed (for Hashimoto's)
• Thyroid ultrasound if there is swelling in the neck

For how to interpret these tests, see the thyroid tests guide.

When is a supplement needed, and when is it not?

Children and adults: According to TEMD 2025, increasing the use of iodized salt can solve the problem in these groups. A healthy adult does not need a routine iodine tablet.

Pregnant and breastfeeding women: TEMD 2025 recommends iodine supplementation in addition to iodized salt for pregnant women in Türkiye. No urine test is needed for this. According to the recommendation box in the guideline's iodine section, supplementation ranges from 100–300 µg per day depending on salt consumption and region of residence. The text of the same guideline gives 100–150 µg for pregnant and breastfeeding women who use iodized salt. In pregnant women whose salt is restricted, this amount rises to 200–250 µg. It is recommended that supplementation begin when pregnancy is being planned and continue until breastfeeding ends. Supplementation can be given as a multivitamin, a combined product with folic acid, or an iodine-only tablet. Your obstetrician determines the right amount and product for you.

Unnecessary situations: TEMD 2025 emphasizes that the use of iodine to boost immunity or protect against radiation has increased and that this is unnecessary. Do not use iodine tablets against radiation without an official warning.

Upper limit and excess

Age group	Daily upper limit	Source
Adults, pregnant, breastfeeding	600 µg	EFSA (SCF)
Ages 15–17	500 µg	EFSA (SCF)
Ages 11–14	450 µg	EFSA (SCF)
Ages 7–10	300 µg	EFSA (SCF)
Ages 1–3 / ages 4–6	200 µg / 250 µg	EFSA (SCF)

In the US, the IOM's adult upper limit is 1,100 µg per day. The European limit is more cautious. TÜBER 2022 also gives a limit of 600 µg for adults.

What does too much iodine do? According to TEMD 2025, excess iodine can cause both goiter and hypothyroidism. In people positive for anti-TPO antibodies, it can accelerate progression to hypothyroidism. In people who have been iodine-deficient for a long time, iodine-induced hyperthyroidism (Jod-Basedow) may occur. According to the NIH, people with autoimmune thyroid disease or iodine deficiency may be affected even by amounts considered safe for the general population.

The seaweed trap: According to the NIH, the iodine content of seaweeds ranges from 16 µg to 2,984 µg per gram. This makes it hard to know how much iodine you get from kelp or seaweed tablets. TEMD 2025 also lists seaweed tablets among products that can cause hypothyroidism.

The hidden total: A pregnancy multivitamin, a separate iodine tablet and a product containing seaweed may be used together. Add up the iodine amounts on the labels and show the list to your physician.

Caution in big cities: TEMD 2025 asks that unnecessary iodine supplementation be avoided in regions such as Istanbul, where the median urinary iodine approaches 200 µg/L. The guideline also stresses that this caution should not undermine protection through iodized salt. This warning is for the general population; TEMD's recommendation of additional iodine in pregnancy and breastfeeding does not change.

Drug and lab test interactions

According to TEMD 2025, the following medicines and products contain iodine or can disrupt thyroid hormone production:

• Amiodarone (a heart rhythm medicine)
• Iodinated contrast agents (CT, angiography)
• Potassium iodide solutions and some expectorants
• Seaweed tablets and iodine-containing skin antiseptics
• Lithium

According to the NIH, iodine can enhance the effect of antithyroid medicines (methimazole, propylthiouracil) when taken together. When potassium iodide is combined with ACE inhibitors or potassium-sparing diuretics, blood potassium can rise. If you take a thyroid medicine, tell your physician or pharmacist about any iodine-containing supplements. Do not change your medicine on your own.

Thyroid scintigraphy and radioactive iodine: According to TEMD 2025, even two weeks of high iodine intake reduces the thyroid's uptake of these agents. The guideline recommends stopping iodine-containing preparations about 4 weeks before the test. Before your appointment, tell the nuclear medicine team about all your supplements and follow their instructions.

In Türkiye

• Mandatory iodization: According to TÜBER 2022, iodization of table salt has been mandatory since 1998 to prevent iodine deficiency. TEMD 2025 states that the necessary legal regulations were completed in July 1999.
• Codex rule: Under the Turkish Food Codex Communiqué on Salt (2013/48), adding 25–40 mg/kg of potassium iodate to table salt is mandatory. Iodine is not mandatory in salt for the food industry. Therefore, the salt in bread and ready-made foods may not be iodized.
• Non-iodized salt: May be sold only for people who should not take iodine, and only in packages of up to 250 g.
• Storage: According to the Communiqué, iodized salt should be stored tightly closed in a cool, dry place away from light.
• Result: According to TEMD 2025, the prevalence of goiter among schoolchildren in Ankara fell from 25% in 1997 to 1.3% in 2007.
• Current data lacking: According to the guideline, the national surveys planned for 2012 and 2015 could not be carried out due to a lack of resources. As a result, the latest national data on schoolchildren date from 2007.
• Supplement approval: You can check whether iodine-containing supplements are approved on the GGBS list of the Ministry of Agriculture and Forestry.

Which doctor should you see?

• Swelling in the neck, fatigue, weight change: Family physician or Internal Medicine; Endocrinology if needed.
• Planning a pregnancy or pregnant: Obstetrics and Gynecology; discuss iodine supplementation.
• If you have Hashimoto's or another thyroid disease: Endocrinology; consult before starting a supplement containing iodine or seaweed.
• Bring with you: Supplement boxes, the package of the salt you use, and your latest thyroid test results.

When to seek emergency care?

• Rapidly growing swelling in the neck or difficulty swallowing: go to the emergency department without waiting. If you are short of breath, call 112 (the emergency number in Türkiye).
• If an iodine solution or a large number of tablets has been swallowed: call the National Poison Information Center at 114 right away; if there is burning in the mouth and stomach or vomiting, call 112.
• If a child has swallowed a product containing iron, call 112 without waiting for symptoms. If they have swallowed another supplement, call the National Poison Information Center at 114; if there is drowsiness, vomiting, breathing difficulty or a seizure, call 112.
• Very fast palpitations, high fever, clouding of consciousness: this may be a thyroid storm; call 112.
• Shortness of breath or a widespread itchy rash after a contrast agent: call 112.

Related guides

• Vitamin and Mineral Guide
• Deficiency risk test
• Thyroid diseases and Hashimoto's guide
• Selenium and Hashimoto's
• Folic acid, iron, vitamin D and iodine in pregnancy
• Pregnancy planning guide
• Hidden salt in ready-made food

What changed? (October 2026)

• Data for Türkiye and the pregnancy recommendation were given according to the TEMD 2025 thyroid guideline. The pregnancy amounts in two sections of the guideline (100–300 µg and 100–150 µg) were shown together.
• Upper limits were taken from EFSA's summary table dated August 2025.
• Reference values for Türkiye were given according to TÜBER 2022. It was explained that the Istanbul pregnancy data are a population indicator. Emergency guidance was updated.
• The current (consolidated) text of the Communiqué on Salt was re-checked in October 2026; the 25–40 mg/kg potassium iodate rule has not changed.

Sources

• Türkiye Endokrinoloji ve Metabolizma Derneği. Tiroid Hastalıkları Tanı ve Tedavi Kılavuzu 2025. https://file.temd.org.tr/Uploads/publications/guides/documents/tiroid2025_11042025.pdf (accessed October 4, 2026)
• Sağlık Bakanlığı. Türkiye Beslenme Rehberi (TÜBER) 2022. https://hsgm.saglik.gov.tr/depo/birimler/saglikli-beslenme-ve-hareketli-hayat-db/Dokumanlar/Rehberler/Turkiye_Beslenme_Rehber_TUBER_2022_min.pdf (accessed October 4, 2026)
• T.C. Gıda, Tarım ve Hayvancılık Bakanlığı. Türk Gıda Kodeksi Tuz Tebliği (No 2013/48). Resmî Gazete 16.08.2013, sayı 28737. https://www.resmigazete.gov.tr/eskiler/2013/08/20130816-15.htm (accessed October 4, 2026)
• T.C. Tarım ve Orman Bakanlığı, Güvenilir Gıda. Bir takviye edici gıdanın onaylı olup olmadığını nereden öğrenebiliriz? February 10, 2026. https://guvenilirgida.tarimorman.gov.tr/Haber/Detay/17314 (accessed October 4, 2026)
• WHO, UNICEF, ICCIDD. Assessment of iodine deficiency disorders and monitoring their elimination: a guide for programme managers. 3rd edition, 2007. https://www.who.int/publications/i/item/9789241595827 (accessed October 4, 2026)
• EFSA. Overview on Tolerable Upper Intake Levels as derived by the SCF and the EFSA NDA Panel. Version 11, August 2025. https://www.efsa.europa.eu/sites/default/files/2024-05/ul-summary-report.pdf (accessed October 4, 2026)
• NIH Office of Dietary Supplements. Iodine: Fact Sheet for Health Professionals. Updated November 5, 2024. https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional/ (accessed October 4, 2026)