Iodine (Urine)
Measures urinary iodine levels to assess iodine intake and nutritional status, particularly important for thyroid hormone production and overall metabolic health.
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Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
What this test measures
This test measures urinary iodine concentration, either from a single spot sample or a 24-hour collection, to assess the body's iodine status. Iodine is an essential trace element that the body cannot produce, so it must be obtained through dietary sources including seafood, dairy products, iodized salt, and certain vegetables. Approximately 90% of ingested iodine is excreted through the kidneys, making urinary iodine concentration a reliable reflection of recent intake.
Iodine's primary function in the body is serving as the raw material for thyroid hormone production. The thyroid gland uses iodine to synthesize thyroxine (T4) and triiodothyronine (T3), hormones that regulate metabolic rate, protein synthesis, and cellular energy production throughout every organ system. Adequate iodine is especially critical during pregnancy and early childhood, when thyroid hormones drive proper brain development, nervous system maturation, and overall growth. This test helps healthcare providers determine whether iodine intake is sufficient, excessive, or deficient, and can guide supplementation decisions.
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals with thyroid disorders or symptoms of thyroid dysfunction, including unexplained fatigue, weight changes, or temperature intolerance, may benefit from iodine assessment to determine if iodine deficiency contributes to their condition.
- Pregnant and breastfeeding women who require higher iodine intake should consider testing, as maternal iodine deficiency can impact fetal brain development and increase the risk of developmental delays in children.
- Those following restrictive diets, including vegans, vegetarians, or individuals avoiding processed foods, may have lower iodine intake since plant-based foods typically contain less iodine than seafood and dairy products.
- People living in areas with iodine-depleted soil or those who primarily consume locally grown foods from inland regions may need monitoring, as geographic variations in soil iodine content can affect dietary intake.
- Individuals taking medications that can interfere with iodine metabolism or those with a history of exposure to iodine-containing contrast agents may benefit from monitoring to ensure proper iodine balance.
What to expect
Preparation
No special preparation is typically required for a spot urine test. Avoid iodine-containing contrast agents or supplements for at least 96 hours before testing if possible.
Sample Type
Collection involves providing either a single spot urine sample or a complete 24-hour urine collection, depending on the specific test ordered.
Collection
For spot urine collection, patients provide a single urine sample at the lab. For 24-hour collection, detailed instructions are provided for collecting all urine over a full day period.
Turnaround
Results are typically available within 2-5 business days after sample collection and processing.
Understanding your results
Results are interpreted using established guidelines that classify urinary iodine concentrations for adults and children: 100 to 199 mcg/L is considered adequate intake, values below 100 mcg/L indicate insufficient intake of varying severity (with lower values signaling greater deficiency), and values above 300 mcg/L may suggest excessive intake. Healthcare providers evaluate iodine results alongside thyroid function tests (particularly TSH), dietary history, and any symptoms of thyroid dysfunction to determine whether the current iodine supply is supporting healthy thyroid hormone production.
| Population | Reference Range | Notes |
|---|---|---|
| Adults | 100-199 mcg/L | WHO-recommended range indicating adequate iodine intake for most healthy adults |
| Pregnant Women | 150-249 mcg/L | Higher range reflects increased iodine needs during pregnancy for fetal development |
| Lactating Women | >100 mcg/L | Minimum threshold for adequate iodine status during breastfeeding |
Reference ranges may vary by laboratory and individual factors. Results should be interpreted by a healthcare provider in the context of your overall health.
What does a “Low” result mean?
Low urinary iodine levels suggest insufficient iodine intake and may be associated with mild deficiency (50-99 mcg/L), moderate deficiency (20-49 mcg/L), or severe deficiency (less than 20 mcg/L). Iodine deficiency can lead to hypothyroidism, characterized by symptoms such as fatigue, weight gain, cold intolerance, and in severe cases, goiter (enlarged thyroid gland). Prolonged iodine deficiency is particularly concerning during pregnancy and early childhood, as it represents the most common preventable cause of intellectual disability worldwide and can affect cognitive development.
What does a “High” result mean?
Elevated urinary iodine levels may indicate excessive iodine intake, which can potentially lead to thyroid dysfunction including both hyperthyroidism and hypothyroidism. High iodine exposure may cause iodine-induced hyperthyroidism (IIH), particularly in individuals with pre-existing thyroid conditions, leading to symptoms such as rapid heart rate, weight loss, muscle weakness, and skin warmth. Excessive iodine intake often results from supplements, iodine-rich foods like seaweed, or medical procedures involving iodine contrast agents.
Privacy & confidentiality
All test results are kept strictly confidential and protected under HIPAA regulations. Results are not shared with insurance companies, employers, or added to your medical records without your explicit consent, ensuring your privacy throughout the testing process.
Frequently asked questions
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Basic urine testing to ensure kidney function is normal for proper iodine excretion interpretation
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Last reviewed: April 2026
CPT Code: 84525
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
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LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
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