Lab result explainedVitamins and mineralsLast updated November 11, 2026

Iodine test: what urine iodine levels mean, the normal range, and why the skin patch test does not work

Iodine test (urine iodine) (Urine iodine) · Urine iodine (spot or 24-hour collection); not part of routine blood panels · reported in µg/L (micrograms per liter) for spot urine; µg/g creatinine for creatinine-corrected results; µg/24 h for timed collections

An iodine test almost always means a urine iodine test, because about 90 percent of the iodine you eat leaves in the urine within a day or two, so the urine concentration mirrors recent intake. For adults the World Health Organization treats a median of 100 to 199 micrograms per liter (µg/L) as adequate, 50 to 99 as mild deficiency, 20 to 49 moderate, under 20 severe, and 300 or more as excessive; in pregnancy the adequate band shifts up to 150 to 249 µg/L. These cut-offs were written for populations, not individuals, and that distinction is the single most important thing to know about this test.

A single spot urine iodine varies by 30 to 40 percent from day to day in the same person depending on what was eaten and how dilute the urine is. One value of 80 µg/L does not mean you are deficient and one value of 250 does not mean you are overloaded; studies show that around 10 separate spot or 24-hour samples are needed to estimate an individual's status to within 20 percent. A 24-hour collection, or a spot value corrected for creatinine, smooths some of this out, and the pattern over several samples is what a clinician reads.

Iodine is the raw material for thyroid hormone, so the practical questions behind an iodine test are usually about the thyroid: a goiter, an unexplained rise in TSH, a plant-based or salt-restricted diet, planning or being in pregnancy, or heavy use of kelp or seaweed supplements. Blood iodine tests exist but are rarely useful, and the iodine skin patch test sold online, where a painted patch of iodine is timed to see how fast it fades, has no scientific basis at all; the rate of fading depends on temperature, humidity and skin, not on your body's iodine stores.

Urine iodine at a glance

What it is: the iodine concentration in a spot or 24-hour urine sample, the standard way to assess recent iodine intake; most dietary iodine is excreted in urine within 24 to 48 hours.
Adults (WHO population cut-offs): 100–199 µg/L adequate; 50–99 mild deficiency; 20–49 moderate; under 20 severe; 200–299 more than adequate; 300 µg/L or higher excessive.
Pregnancy: 150–249 µg/L adequate; under 150 insufficient; 500 or higher excessive. Breastfeeding: 100 µg/L or higher adequate.
One sample cannot diagnose an individual: day-to-day variation is 30 to 40 percent, and about 10 collections are needed for a reliable personal estimate. Read it with TSH and free T4.
The US median is around 130 to 145 µg/L, adequate overall, but pregnant women and people who avoid dairy, seafood and iodized salt commonly fall under 100.
The iodine skin patch test and the 50 mg 'iodine loading test' are not validated and should not guide supplementation.

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What Urine iodine measures

Iodine is absorbed almost completely from food, taken up by the thyroid in the amount it needs (about 60 to 80 µg a day in an adult), and the surplus is cleared by the kidneys. Because the kidney does not conserve iodine, urinary excretion tracks intake over the previous day or two with a lag of a few hours. The lab measures iodine in urine by inductively coupled plasma mass spectrometry or the older Sandell-Kolthoff colorimetric reaction, and reports it as micrograms per liter for a spot sample, micrograms per gram of creatinine, or micrograms per 24 hours for a timed collection.

The WHO cut-offs are designed to describe the median of a population surveyed with single spot samples, where individual noise averages out. Applied to one person, a spot value reflects what you ate yesterday, how much water you drank and the time of day; a first-morning sample from someone who skipped dinner reads low, and a sample the day after a sushi dinner reads high. Correcting for urine creatinine helps with dilution but introduces its own error in people with low or high muscle mass. A 24-hour collection avoids the dilution problem and is the preferred individual test, with roughly 100 µg per day or more considered adequate for a non-pregnant adult.

Other markers add context. Serum thyroglobulin rises when the thyroid is working harder to trap iodine and falls back with repletion, so a median thyroglobulin under 13 µg/L in children indicates adequate iodine in populations; it is less established for individuals and is uninterpretable if thyroglobulin antibodies are present. TSH is a poor iodine marker in adults because the thyroid compensates until deficiency is moderate to severe, but a TSH above 5 mIU/L in a newborn screen is a sensitive population indicator. Serum iodine (normal roughly 40 to 90 µg/L) is used mainly to detect gross excess after contrast dye or amiodarone, not deficiency.

Normal range for Urine iodine

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

Group	Typical range (µg/L (micrograms per liter) for spot urine; µg/g creatinine for creatinine-corrected results; µg/24 h for timed collections)	Notes
Severe deficiency (population median)	Below 20 µg/L	Associated with goiter in most of the population, hypothyroidism and, in pregnancy, impaired fetal brain development. Rare in the US.
Moderate deficiency	20–49 µg/L	Goiter common, thyroid hormone production starts to fall. Seen in regions without iodized salt.
Mild deficiency	50–99 µg/L	Thyroid enlarges slightly to compensate; TSH usually still normal. Common in people who avoid dairy, eggs, seafood and iodized salt.
Adequate, non-pregnant adults and children	100–199 µg/L	WHO target band. US median in national surveys is about 130 to 145 µg/L.
More than adequate	200–299 µg/L	No harm for most people; a modest increase in autoimmune thyroiditis and hypothyroidism in susceptible individuals in population studies.
Excessive	300 µg/L or higher	Risk of iodine-induced hypothyroidism (especially with Hashimoto's) or hyperthyroidism (with nodular goiter). Values in the thousands occur after kelp supplements, iodinated contrast or amiodarone.
Pregnancy	150–249 µg/L adequate; below 150 insufficient; 250–499 above requirements; 500 or higher excessive	The fetus depends entirely on maternal iodine for its thyroid hormone in the first trimester. US pregnant women have a median near 140 to 150 µg/L, borderline.
Breastfeeding	100 µg/L or higher adequate	Iodine is concentrated into breast milk, so the mother's urine runs lower than her intake would suggest.
24-hour urine iodine, adults	Roughly 100–300 µg per 24 hours typical with adequate intake	Below about 100 µg/day over repeated collections suggests insufficient intake. Some labs print 24-hour reference intervals up to 400 to 500 µg/day; use the printed range.

High urine iodine

A high urine iodine means your recent intake was high, and the first question is what you ate or were given in the previous few days. Values of 300 to 1,000 µg/L usually trace to seaweed, kelp or iodine supplements, iodine-rich multivitamins or a lot of dairy; values in the thousands or higher almost always follow iodinated contrast dye from a CT scan or angiogram, which can raise urine iodine for 4 to 8 weeks, or amiodarone, which contains 75 mg of iodine in each 200 mg tablet. Povidone-iodine skin preparation, some expectorants and water-purification tablets are other sources.

For most people a transiently high value is harmless, because a healthy thyroid shuts down hormone production briefly when flooded with iodine (the Wolff-Chaikoff effect) and then adapts within a couple of weeks. The exceptions are people whose thyroids cannot escape that shutdown, particularly those with Hashimoto's thyroiditis, a history of thyroid surgery or radioiodine, and newborns, who can slip into hypothyroidism, and people with long-standing nodular goiter or latent Graves' disease, in whom a large iodine load can trigger hyperthyroidism (the Jod-Basedow phenomenon) weeks to months later.

The US tolerable upper intake level for adults is 1,100 µg a day. Sustained intake above that, which is easy to reach with kelp capsules (some contain 1,000 to 2,000 µg or more per dose) or daily kombu, raises the rate of hypothyroidism and thyroid autoimmunity in population studies, and a persistently high urine iodine in someone with a rising TSH or new thyroid antibodies is a reason to stop the source rather than add thyroid medication straight away.

Common causes

Kelp, bladderwrack and seaweed supplements
Kelp tablets commonly deliver 500 to 2,000 µg per serving and some far more, and the label is often inaccurate. These are the most frequent cause of a urine iodine over 500 µg/L in someone who feels well, and a common cause of iodine-induced hypothyroidism.
Seaweed in the diet
Iodine content varies a thousandfold: nori used for sushi has roughly 16 to 43 µg per gram, wakame about 100 to 400, and kombu (kelp) 1,000 to nearly 3,000 µg per gram, so a single serving of kombu broth can exceed the upper limit several times over.
Iodinated contrast dye
A CT or cardiac catheterization contrast dose contains grams of iodine, pushing urine iodine into the thousands for days and keeping it elevated for 4 to 8 weeks. A test in this window is uninterpretable, and about 5 percent of people develop transient thyroid dysfunction afterward.
Amiodarone
Each 200 mg tablet releases about 6 to 7 mg of free iodine, 40 times the daily requirement, and the drug is stored in fat for months. Urine iodine is high throughout treatment and thyroid function is monitored every 6 months because both hypothyroidism and hyperthyroidism occur.
High-dose iodine or potassium iodide supplements
Products sold for 'thyroid support', nascent iodine drops and the 12.5 to 50 mg daily protocols promoted online deliver 100 to 300 times the RDA. There is no evidence they help and good evidence they cause thyroid dysfunction.
Topical and antiseptic iodine
Povidone-iodine applied to large wounds or burns, used as a mouthwash, or absorbed through the skin of newborns during procedures is enough to raise urine iodine and transiently suppress the thyroid.
Prenatal vitamins plus iodine-rich diet
A 150 µg prenatal supplement on top of generous dairy, eggs and seafood commonly puts pregnant women in the 250 to 500 µg/L 'above requirements' band, which is not harmful; values over 500 µg/L in pregnancy usually mean an additional kelp or iodine product.
Dilute or concentrated urine
A spot sample on a day of low fluid intake reads higher than the same intake would in dilute urine. Creatinine correction or a 24-hour collection sorts this out.

Symptoms that can go with it

Usually none; a high urine iodine after a seafood meal or a scan is a number, not an illness
With iodine-induced hypothyroidism: fatigue, cold intolerance, weight gain, dry skin, constipation, puffy face
With iodine-induced hyperthyroidism: palpitations, heat intolerance, weight loss, tremor, anxiety, insomnia, usually weeks after a large iodine load in someone with nodules
Goiter or a feeling of neck fullness; chronic iodine excess enlarges the thyroid just as deficiency does
Metallic taste, burning mouth, excess saliva, acne-like rash or stomach upset with very high supplement doses (iodism)
A newborn with poor feeding, jaundice or low temperature after maternal high-dose iodine exposure or topical iodine at delivery

Low urine iodine

A low urine iodine suggests your recent intake has been below requirements, but one spot value under 100 µg/L is weak evidence on its own. The lab result reflects the last day or two, and a low reading after a day of light eating, lots of water or no dairy is common in people who are perfectly replete. The result becomes meaningful when it is repeated (ideally several spot or 24-hour samples), when it is well below the band (under 50 µg/L), or when it fits a diet that is genuinely short of iodine: little or no dairy, eggs or seafood, non-iodized or sea salt, and no supplement containing iodine.

When intake really is low, the thyroid compensates for a long time. It traps a larger fraction of the available iodine, enlarges slightly, and keeps TSH and free T4 in the normal range until deficiency is moderate (urine iodine persistently under 50 µg/L). That is why iodine deficiency is usually silent in adults and why a normal TSH does not exclude it. The exceptions are pregnancy and infancy: the fetal brain depends on maternal thyroid hormone in the first trimester and on maternal iodine afterward, and even mild maternal deficiency (median 50 to 150 µg/L) has been linked in observational studies to small reductions in children's IQ and reading scores, which is why the RDA rises to 220 µg in pregnancy and 290 µg while breastfeeding and why the American Thyroid Association recommends a prenatal supplement containing 150 µg of iodide.

The US as a whole is iodine sufficient because of iodized salt and dairy, but intake has halved since the 1970s, only about half of table salt sold is iodized, salt used in processed food is almost never iodized, and plant-based milks contain little iodine unless fortified. Pregnant women in national surveys have a median of around 140 to 150 µg/L, just under the 150 target, and vegans, people on strict low-salt diets and those who have cut dairy are the groups most often found to be low.

Common causes

Little or no dairy, eggs or seafood
Dairy supplies roughly half the iodine in the typical US diet (about 85 µg per cup of milk, from iodine in feed and sanitizing solutions), with eggs (about 25 µg each) and ocean fish (about 100 µg per 3 oz of cod) next. Vegan and dairy-free diets remove most of it unless replaced by fortified foods or a supplement.
Non-iodized salt, sea salt or a low-salt diet
A quarter teaspoon of US iodized salt provides about 70 µg of iodine; sea salt, kosher salt and Himalayan salt contain essentially none, and the salt in restaurant and processed food is not iodized. Someone who cooks with specialty salt and eats little dairy can easily fall under 100 µg a day.
Pregnancy and breastfeeding
Requirements rise by about 50 percent because the kidneys clear more iodine, the fetus takes a share, and breast milk concentrates it. Only about 60 percent of US prenatal vitamins contain iodine, and many that do contain less than the 150 µg recommended.
Goitrogen-heavy diets with marginal intake
Thiocyanates from cassava, raw cruciferous vegetables in large quantities, millet, soy and cigarette smoke compete with iodine uptake. They only matter when iodine intake is already low; a normal intake overrides them.
Dilute urine or a single unrepresentative sample
High fluid intake, a sample after a day of fasting or illness, or a first-morning void in someone who ate lightly the night before all read low. Repeat samples or a 24-hour collection, or ask for creatinine correction.
Selenium or iron deficiency alongside low iodine
Both are needed for thyroid hormone synthesis and metabolism, and coexisting deficiency worsens the thyroid consequences of low iodine without changing the urine iodine itself.
Certain medications and dialysis
Loop diuretics increase urinary losses slightly, and iodine handling is altered in advanced kidney disease and dialysis; both are rare causes of true deficiency in the US.

Symptoms that can go with it

Usually none in adults; mild deficiency is silent for years
A visible or palpable swelling at the front of the neck (goiter), the earliest sign of chronic deficiency
If hypothyroidism develops: fatigue, cold intolerance, dry skin, constipation, weight gain, slowed thinking, heavier periods
In pregnancy: usually no maternal symptoms; the concern is fetal brain development and a higher rate of miscarriage and stillbirth with moderate to severe deficiency
In infants and children: poor growth, developmental delay, and in severe maternal deficiency, congenital hypothyroidism
Hoarseness or difficulty swallowing if a goiter becomes large

Read it alongside

TSH — the first thyroid check; it stays normal in mild iodine deficiency and rises only when deficiency is moderate to severe, or when iodine excess has suppressed the gland.
Free T4 and free T3 — in deficiency the thyroid preferentially makes T3, so free T3 may be normal or high while free T4 drifts down; both fall in overt hypothyroidism.
Thyroglobulin — rises when the thyroid is straining to trap iodine and falls with repletion; a useful second marker of iodine status when thyroglobulin antibodies are absent.
TPO antibodies and thyroglobulin antibodies — identify Hashimoto's thyroiditis, the group most likely to become hypothyroid when exposed to excess iodine.
Urine creatinine — used to correct a spot urine iodine for dilution (µg/g creatinine), which reduces, but does not remove, sample-to-sample scatter.
Ferritin and selenium — iron and selenium deficiency impair thyroid hormone production and amplify the effect of low iodine; ferritin is routinely available, serum selenium less so.
hCG and prenatal panel — in pregnancy, urine iodine is interpreted against the higher 150 µg/L target and the 220 µg daily requirement.
Thyroid ultrasound — not a lab test, but it measures gland volume and nodules, the long-term signature of both deficiency and excess.

What usually happens next

A single low or high spot value is repeated, ideally as a 24-hour collection or several spot samples on ordinary eating days, before anything is concluded; ask for creatinine correction if only spot samples are practical.
Expect TSH and free T4 alongside, and thyroid antibodies if TSH is abnormal, because the thyroid's response, not the urine number, decides whether anything needs treating.
Go through your sources with the clinician: type of salt at home, servings of dairy, eggs and fish per week, plant milks and whether they are fortified, any multivitamin, prenatal or kelp product, recent CT contrast, and medications such as amiodarone.
If you are pregnant, planning pregnancy or breastfeeding and your prenatal vitamin does not list 150 µg of iodine (as potassium iodide), ask about switching; this is the group where correcting intake matters most.
If you take kelp, bladderwrack, sea moss or an iodine protocol and your urine iodine or TSH is high, the usual advice is to stop the product and recheck thyroid function in 6 to 8 weeks rather than start medication immediately.
If urine iodine was measured within 8 weeks of a contrast scan, treat the result as uninterpretable and repeat later.

Diet, lifestyle and natural levers with evidence

What can move Urine iodine once the cause is known. Nothing here replaces finding the cause.

Iodized salt in home cooking

Strong evidence

Salt iodization is the intervention that eliminated goiter in the US Midwest in the 1920s and remains the WHO-recommended strategy worldwide; universal programs raise population median urine iodine from under 50 to over 100 µg/L within a year. US iodized salt contains about 45 µg of iodine per gram, so half a teaspoon a day in cooking (about 140 µg) covers most of an adult's 150 µg requirement. Sea salt, kosher salt and Himalayan salt are not iodized unless the label says so, and the salt in processed and restaurant food almost never is.

Use it in place of other salt, not in addition; people on a sodium-restricted diet for blood pressure or heart failure should get iodine from dairy, eggs, fish or a supplement instead.

Dairy, eggs and ocean fish

Moderate evidence

In US national surveys, people who drink milk daily have a median urine iodine about 50 µg/L higher than those who do not, and dairy supplies roughly half of US iodine intake. A cup of milk or yogurt provides about 85 µg, an egg about 25 µg, 3 ounces of cod about 100 µg and a serving of shrimp about 35 µg. Two to three servings a day from this group, with iodized salt, reliably keeps spot urine iodine in the 100 to 199 µg/L band in intervention and observational studies.

Plant milks contain little iodine unless fortified; check the label if dairy is excluded.

A supplement with 150 µg iodide, especially before and during pregnancy

Moderate evidence

The American Thyroid Association, the American Academy of Pediatrics and the Endocrine Society recommend that women who are pregnant, breastfeeding or planning pregnancy take a daily supplement containing 150 µg of iodine as potassium iodide, which raises median urine iodine by roughly 50 to 100 µg/L in trials. Benefits for child cognition are clear when maternal deficiency is moderate to severe; in mild deficiency, the largest randomized trial (Thailand and India, 2017) found no measurable IQ difference at 5 to 6 years, so the supplement is insurance rather than a proven brain enhancer. For non-pregnant adults who avoid dairy and iodized salt, a multivitamin with 150 µg is enough.

Do not exceed 1,100 µg a day in total from all sources. People with Hashimoto's, thyroid nodules or on thyroid medication should discuss any iodine supplement, since both deficiency and excess can shift thyroid function.

Seaweed, in moderation and the right kind

Preliminary evidence

A sheet of nori (about 3 g) supplies roughly 50 to 130 µg of iodine, a sensible amount, whereas kelp and kombu contain 1,000 to nearly 3,000 µg per gram, so a few grams can deliver 10 times the upper limit. Case series and Japanese population data show that regular kombu intake or kelp supplements raise urine iodine into the thousands and cause reversible hypothyroidism and goiter. Occasional nori or wakame is a reasonable iodine source; kelp capsules and daily kombu are not, and the iodine content printed on supplement labels is frequently wrong by severalfold.

Avoid kelp, bladderwrack and sea moss supplements in pregnancy, with Hashimoto's or nodular goiter, and alongside thyroid medication. Seaweed can also concentrate arsenic and heavy metals.

Correcting iron and selenium shortfalls

Moderate evidence

Thyroid peroxidase, the enzyme that attaches iodine to thyroglobulin, needs iron, and the enzymes that activate thyroid hormone need selenium. In trials in iodine-deficient children, iron repletion improved the response to iodized salt (goiter rates fell further), and selenium status modifies thyroid outcomes of both low and high iodine intake. A ferritin check is worthwhile when iodine is low and TSH is drifting up; selenium needs are met by one to two Brazil nuts or a diet with fish, eggs and whole grains, and supplements above 200 µg a day add no benefit.

Selenium above 400 µg a day is toxic; Brazil nut content is variable, so do not eat them by the handful.

When to see a clinician promptly

A rapidly enlarging neck swelling, or a goiter with difficulty swallowing, breathing or a change in voice.
Symptoms of hyperthyroidism (palpitations, a resting heart rate over 100, tremor, weight loss, heat intolerance) in the weeks to months after a large iodine exposure such as contrast dye, kelp supplements or starting amiodarone; a heart rate over 120 with confusion, fever or agitation is a possible thyroid storm and an emergency.
You are pregnant with a urine iodine under 100 µg/L, a TSH above 2.5 to 4 mIU/L (lab and trimester dependent) or a goiter, so thyroid function and supplementation can be sorted out early in pregnancy.
A newborn exposed to high-dose maternal iodine, kelp or topical iodine who is feeding poorly, jaundiced, unusually sleepy or cold; congenital hypothyroidism is treatable but time-sensitive.
Urine iodine persistently over 500 µg/L or any thyroid symptoms while taking an iodine, kelp or 'nascent iodine' product, so the product can be reviewed and thyroid function checked.
Symptoms of hypothyroidism (fatigue, cold intolerance, constipation, weight gain, dry skin) with a very low or very high urine iodine, so TSH and free T4 can be measured.

Frequently asked questions

What is the normal range for urine iodine?

For non-pregnant adults the WHO adequate band is 100 to 199 µg/L; 50 to 99 is mild deficiency, 20 to 49 moderate, under 20 severe, 200 to 299 more than adequate and 300 or higher excessive. In pregnancy, 150 to 249 µg/L is adequate and under 150 insufficient. These cut-offs were set for population medians; for one person, a single spot sample can be off by 30 to 40 percent, so repeat samples or a 24-hour collection are needed before calling someone deficient or overloaded.

How do I test my iodine levels?

Ask for a urine iodine test, either a spot sample (reported in µg/L or µg per gram of creatinine) or a 24-hour collection (µg per day). Because intake varies daily, the most reliable approach is several samples on ordinary eating days, and the result should be read with TSH and free T4. A blood iodine test is rarely helpful except after contrast dye or amiodarone, and home kits that use a skin patch or hair sample do not measure iodine status.

Is the iodine patch test accurate?

No. The patch test, where tincture of iodine is painted on the skin and the time it takes to fade is supposed to show deficiency, has never been validated and is not used by any medical laboratory. Iodine on the skin disappears mainly by evaporation (sublimation), and the rate depends on temperature, humidity, airflow, skin oils and the concentration used, not on how much iodine your body holds. Only a small, variable fraction is absorbed. A fast-fading patch is not a reason to take iodine.

What is the iodine loading test and is it valid?

It involves swallowing a 50 mg dose of iodine (more than 300 times the RDA) and measuring how much appears in a 24-hour urine, with less than 90 percent excretion labeled 'deficient'. The 90 percent threshold was never established in controlled studies, the body does not handle a pharmacologic dose the way it handles dietary iodine, and the test is used to justify high-dose iodine protocols that cause thyroid dysfunction. Thyroid and nutrition societies do not recognize it.

What are the symptoms of iodine deficiency?

In adults, usually none until it is moderate to severe. The earliest sign is a goiter, a painless enlargement of the thyroid at the front of the neck. If hypothyroidism develops there is fatigue, cold intolerance, weight gain, dry skin, constipation, slowed thinking and heavier periods. In pregnancy the mother often feels fine while the fetus is affected, which is why the recommendation to take 150 µg of iodine in a prenatal vitamin does not depend on symptoms or testing.

How much iodine do I need, and how do I get it without supplements?

The RDA is 150 µg a day for adults, 220 µg in pregnancy and 290 µg while breastfeeding, with an upper limit of 1,100 µg. Half a teaspoon of iodized salt in cooking (about 140 µg), a cup of milk or yogurt (about 85 µg), an egg (about 25 µg) or 3 ounces of cod (about 100 µg) each contribute. Sea salt, kosher salt, processed-food salt and most plant milks contain almost none, so people who rely on those and avoid dairy and fish are the ones who fall short.

Can too much iodine cause thyroid problems?

Yes. Sustained intake above about 1,100 µg a day, common with kelp supplements or daily kombu, triggers hypothyroidism in people with Hashimoto's or a previously treated thyroid and hyperthyroidism in people with nodular goiter, and it raises thyroid antibody rates in populations. A single large exposure such as CT contrast is harmless for most people but causes transient thyroid dysfunction in about 5 percent. More is not better; the goal is the 100 to 299 µg/L band, not the highest number possible.

Does iodine deficiency cause hypothyroidism or Hashimoto's in the US?

Rarely. Over 90 percent of hypothyroidism in the US is autoimmune (Hashimoto's) or follows thyroid surgery or radioiodine, not iodine deficiency; the population is iodine sufficient thanks to iodized salt and dairy. Adding iodine to a Hashimoto's diet does not help and can make hypothyroidism worse. Deficiency becomes a plausible cause only with a clearly low-iodine diet, repeated low urine values and a goiter without antibodies.

References

Iodine: fact sheet for health professionals. National Institutes of Health, Office of Dietary Supplements (2024)View source
World Health Organization, UNICEF, International Council for Control of Iodine Deficiency Disorders. Assessment of iodine deficiency disorders and monitoring their elimination: a guide for programme managers, 3rd edition. World Health Organization (2007)
Zimmermann MB, Andersson M. Assessment of iodine nutrition in populations: past, present, and future. Nutrition Reviews (2012)
König F, Andersson M, Hotz K, Aeberli I, Zimmermann MB. Ten repeat collections for urinary iodine from spot samples or 24-hour samples are needed to reliably estimate individual iodine status in women. Journal of Nutrition (2011)
Alexander EK, Pearce EN, Brent GA, et al.. 2017 Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and the postpartum. Thyroid (2017)
Leung AM, Braverman LE. Consequences of excess iodine. Nature Reviews Endocrinology (2014)
Leung AM, Pearce EN, Braverman LE. Iodine content of prenatal multivitamins in the United States. New England Journal of Medicine (2009)
Perrine CG, Herrick KA, Gupta PM, Caldwell KL. Iodine status of pregnant women and women of reproductive age in the United States. Thyroid (2019)
Gowachirapant S, Jaiswal N, Melse-Boonstra A, et al.. Effect of iodine supplementation in pregnant women on child neurodevelopment: a randomised, double-blind, placebo-controlled trial. Lancet Diabetes and Endocrinology (2017)
Teas J, Pino S, Critchley A, Braverman LE. Variability of iodine content in common commercially available edible seaweeds. Thyroid (2004)
Council on Environmental Health; Rogan WJ, Paulson JA, Baum C, et al.. Iodine deficiency, pollutant chemicals, and the thyroid: new information on an old problem. Pediatrics (2014)
Iodine deficiency. Merck Manual Professional Version (2024)

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This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.